Công bố quốc tế trong lĩnh vực kiến trúc, xây dựng (Tuần 3 tháng 5-2021)
Trong số này chúng tôi xin giới thiệu tới quý độc giả những nội dung chính của các công bố quốc tế đăng tải trên ScienceDirect và Springer Nature do Cục Thông tin khoa học và công nghệ quốc gia (NASATI) mua quyền truy cập như sau:
Quy hoạch đô thị:
- Mô hình vi quy trình địa lý: Xem xét quá trình mở rộng đô thị toàn cầu từ quan điểm định hướng quy trình
- Ước tính các khu vực tắc nghẽn và chỉ số thời gian di chuyển dựa trên dữ liệu động (FCD)
- Tác động của bố cục và quy mô không gian đô thị đối với khí hậu địa phương: nghiên cứu điển hình ở Bắc Kinh
- Lập mô hình phát triển đô thị và mức độ ảnh hưởng của nó trước nguy cơ lũ lụt sông ở Đông Nam Á
- Ra quyết định phát triển đô thị: Áp dụng phương pháp đánh giá kết hợp từ kinh nghiệm của Ý
Khoa học và công nghệ trong lĩnh vực xây dựng:
- Hiệu suất nhiệt của các tòa nhà chung cư dưới tác động tổng hợp của hiện tượng nóng lên toàn cầu và cục bộ
- Thiết kế cấu trúc của một ngôi nhà bền vững tính đến hiệu quả sử dụng năng lượng và nước
- Khảo sát thực nghiệm về tính năng địa chấn trong mặt phẳng của các bức tường xây bị hư hỏng được sửa chữa bằng lớp phủ cốt thép phun vữa
- Đánh giá so sánh các tác động môi trường từ ba trường hợp thi công mặt đường nhựa tiên tiến
-Vật liệu xây dựng:
- Bê tông nhẹ dựa trên vỏ lúa mì và cây gai dầu làm cốt liệu sinh học và chất kết dính magie oxysulfate biến tính: Cấu trúc vi mô và hiệu suất công nghệ
- Khung định hướng bền vững cho việc áp dụng các sản phẩm phụ công nghiệp vào lớp nền của các con đường
Xin trân trọng giới thiệu!
QUY HOẠCH ĐÔ THỊ
1. Geographic micro-process model: Understanding global urban expansion from a process-oriented view
Computers, Environment and Urban Systems, Volume 87, May 2021, 101603
Urban expansion across the globe accelerates land cover change and significantly influences the environment and human beings. Measuring the urban expansion process can help us better understand urban expansion dynamics and contribute to urban growth simulation and spatial planning. By using urban land density (defined as the proportion of the built-up area to the buildable area) as a spatial variable, we propose a new model to fit urban land density from the city center outwards (distance-decay rule), based on the assumption that urban shapes are formulated by the accumulation of micro-processes of urban growth. The model is based on simple math with only two parameters that clearly denote urban process characteristics. Using a sample set of 112 large cities around the world at three time points (1990, 2000, and 2014), the proposed model fitted urban expansion data very well, verifying its applicability. One parameter in the model that describes the density gradient can be used to measure the compactness of a city. The model can be easily extended to fit the intermediate process of a given time span and provide a clear indicator of the compactness of the process. The results of our case study clearly show disparities of global cities in terms of urban land compactness. For example, cities in Latin America and the Caribbean are the most compact, cities in Europe and East Asia are moderately compact, and cites in the United States, Canada, and Australia are the most sprawling. Furthermore, we identified a path dependence of urban expansion patterns as well as uneven compactness change trajectories in rapidly urbanizing areas.
2. Estimating congestion zones and travel time indexes based on the floating car data
Computers, Environment and Urban Systems, Volume 87, May 2021, 101604
Efficiently predicting traffic congestion benefits various traffic stakeholders, from regular commuters and logistic operators to urban planners and responsible authorities. This study aims to give a high-quality estimation of traffic conditions from a large historical Floating Car Data (FCD) with two main goals: (i) estimation of congestion zones on a large road network, and (ii) estimation of travel times within congestion zones in the form of the time-varying Travel Time Indexes (TTIs). On the micro level, the traffic conditions, in the form of speed profiles were mapped to links in the road network. On the macro level, the observed area was divided into a fine-grained grid and represented as an image where each pixel indicated congestion intensity. Spatio-temporal characteristics of congestion zones were determined by morphological closing operation and Monte Carlo simulation coupled with temporal clustering. As a case study, the road network in Croatia was selected with spatio-temporal analysis differentiating between the summer season and the rest of the year season. To validate the proposed approach, three comparisons were conducted: (i) comparison to real routes’ travel times driven in a controlled manner, (ii) comparison to historical trajectory dataset, and (iii) comparison to the state-of-the-art method. Compared to the real measured travel times, using zone’s time-varying TTIs for travel time estimation resulted in the mean relative percentage error of 4.13%, with a minor difference to travel times estimated on the micro level, and a significant improvement compared to the current Croatian industrial navigation. The results support the feasibility of estimating congestion zones and time-varying TTIs on a large road network from FCD, with the application in urban planning and time-dependent routing operations due to: significant reduction in the data volume without notable quality loss, and meaningful reduction in the pre-processing computation time.
3. Detecting anomalous spatial interaction patterns by maximizing urban population carrying capacity
Computers, Environment and Urban Systems, Volume 87, May 2021, 101616
Rapid urbanization in China has prompted plenty of urban facilities to be constructed with the expectation of harmonizing with the rapid growth of urban population. However, regarding the spatial interactions produced by cross-area human mobility, the diversity and variability of residents’ trip requirements inevitably cause the deviations of the real interaction patterns from the optimal status determined by the current allocation of urban facilities. To maximize the utility of urban facility allocation, we designed a bipartite network-based approach to explore anomalous spatial interaction patterns within cities. First, considering the potential area attractiveness, a weighted origin-destination bipartite network was constructed to structure the spatial interactions between traffic analysis zones. Then, a branch and bound (BnB) based augmenting path algorithm was proposed to optimize the distribution of spatial interactions, which can maximize the urban population carrying capabilities. Finally, anomalous interaction patterns causing both overload and underload were detected through comparisons between the actual and optimal spatial interaction distribution. The experimental results show that the two types of anomalous interaction patterns have significantly different spatial distribution characteristics. Through further analyzing the relationships between the two types of anomalous interaction patterns and urban evolution process, this study can also provide targeted decision supports for the accommodating of urban facility allocations to the distributions of resident trips in space.
4. Driving as a commuting travel mode choice of car owners in urban China: Roles of the built environment
Cities, Volume 112, May 2021, 103114
Car dependency has been well recognized in low-density urban areas in developed countries, where travel demand management (TDM) has focused on providing transit-riding and non-motorized modes of transport, rather than restricting car ownership. In contrast, many megacities in China have adopted vehicle quota systems, fearing that additional car owners will become addicted to driving despite the soaring travel congestion and air pollution. This study investigated two research questions: Under what built environment characteristics would China’s car owners give up driving for other commuting modes? Are the effects of built environment characteristics on car ownership and commuting mode choice spatially heterogeneous across zones? We use a household travel survey in Nanjing city, where no car quota system exists, to examine car owners’ commuting mode choice. Innovatively, a multilevel discrete choice model with sample selection was used to reveal the effects of the built environment on car ownership and commuting mode choice simultaneously. We found significant spatial heterogeneities in car ownership and commuting mode choice across traffic analysis zones, while the built environment was found to play an important role. Our findings suggest that Chinese urbanites may be less addicted to driving than they appear, and city governments should be more progressive in regulating driving by improving the urban form.
5. The suitability of the urban local climate zone classification scheme for surface temperature studies in distinct macroclimate regions
Urban Climate, Volume 37, May 2021, 100823
The Local Climate Zone (LCZ) classification scheme, initially designed to distinguish between standard built (urban) and non-built (land cover) types in terms of screen-level air temperature relevant for urban heat island (UHI) studies, has been widely used for land surface temperature (LST) and surface urban heat island (SUHI) studies. However, some concerns remain about the global suitability of the scheme for LST and SUHI studies in different macroclimate regions. By analyzing and comparing a large number of representative LCZ sites and multi-year remotely-sensed LST data, the aim of this work is twofold. Firstly, to study the suitability of the LCZ scheme, with a focus on the built types, for surface temperature studies in four distinct macroclimate regions, namely, the tropical, the arid, the temperate and the cold. Secondly, to understand the influence of the macroclimate region on the LST and SUHI characteristics of the standard LCZ built types. Results show that the urban LCZ standard scheme is applicable, with varying degrees, to all macroclimate regions other than the arid, where a LCZ subclassification might be essential. Also, it has been demonstrated that most LCZ built types exhibit significantly different LST and SUHI characteristics across the remaining macroclimate regions.
6. Impacts of urban spatial layout and scale on local climate: A case study in Beijing
Sustainable Cities and Society, Volume 68, May 2021, 102767
Based on the meteorological data (2009–2018) acquired by high-density automatic meteorological stations (AMSs) in Beijing, the influences of urbanization on urban heat island (UHI), wind, and humidity were described by UHI, wind speed ratio (Wsr), and specific humidity ratio (qr), respectively. For the 37 AMSs in central Beijing, the relationships between UHI, Wsr, and qr and six spatial morphological parameters (building height (BH), building density (BD), floor area ratio, sky view factor, frontal area index, and roughness length (RL)) and two land surface parameters (vegetation coverage and impervious cover) in the range of 200−3000 m from the station were studied. The scale effect of each parameter on local climate was also studied. The results showed that individually, these parameters account for 46.8–79.6 % of the change in UHI, 25.6–52.8 % of the change in Wsr, and 25.7–29.3 % of the change in qr. The impact of spatial morphological parameters on local climate has surpassed that of land surface parameters. The parameters that make the largest contributions to the annual average UHI, Wsr, and qr are RL, BH, and BD, respectively. The optimal influencing ranges of the spatial morphological parameters on UHI, Wsr, and qr are 800−1000 m, 1600−2600 m, and 1200−1400 m, respectively.
7. Modeling urban development and its exposure to river flood risk in Southeast Asia
Computers, Environment and Urban Systems, Volume 87, May 2021, 101620
Countries in Southeast Asia have been developing quickly from a predominantly rural to predominantly urban society, leading to a rapid increase in urban land. This increase in urban land has mainly occurred in river deltas and floodplains, exposing humans and human assets to flood hazard. Here we present an assessment of current and future flood risk in five countries of mainland Southeast Asia, using a new modeling approach that accounts for differences in urban land systems. To that effect we mapped urban land on a rural-urban gradient and projected urban development until the year 2040 in two contrasting scenarios. The urban expansion scenario mainly projects the development of new urban areas, while the intensification emphasizes an increase in the number of inhabitants in already existing urban areas. Subsequently, we assessed the expected annual damage due to flood risk, using country specific exposure values for different land-system classes along the rural-urban gradient, based on typical construction materials. Results indicate that expected annual flood damage will increase in all countries and in both scenarios, ranging from +8% in Thailand to +211% in Laos. We showed that preferable development pathways are context dependent. In Cambodia and Laos, the increase in flood risk was largest for the intensification scenario, while for Myanmar, Thailand and Vietnam, the increase in flood risk was largest in the urban expansion scenario.
8. Research on outdoor thermal comfort of high-density urban center in severe cold area
Building and Environment, Available online 7 May 2021, 107938
With high intensity of urban land development and dense population, urban high-density central area has obvious heat island effect, which has a great impact on thermal comfort. Taking Qiulin commercial district, the high-density central area of Harbin as the research object, this paper uses physical measurement and questionnaire survey to evaluate the outdoor thermal comfort. The results show that: (1) In high-density blocks of Harbin, there is a strong correlation between TCV and TSV, which is mainly affected by air temperature and globe temperature. And the correlation is stronger in transition season and winter than in summer; (2) The applicability PET in severe cold area was verified. The logistic regression method was used to obtain the range of neutral PET [12.99 °C, 19.89 °C] and the acceptable PET [5.14 °C, 27.15 °C]. At the same time, the 11-point TSV scale was verified to be accurate in assessing the thermal sensation in severe cold area; (3) Preferred PET in summer and transition season were 24.8 °C and 23.5 °C, respectively. Temperature expectation is the main factor influencing the difference of preferred temperature between cold and hot seasons; (4) Residents in severe cold area have become psychologically adapted to the cold environment due to long-term exposure to cold conditions, so that people are less sensitive to low temperatures in winter. In this situation it is important to have a general understanding of the outdoor thermal comfort in severe cold regions, which can guide planners to a better urban design.
9. Decision making in urban development: The application of a hybrid evaluation method for a critical area in the city of Turin (Italy)
Sustainable Cities and Society, Available online 19 May 2021, 103028
Smart cities and sustainable neighbourhoods are increasingly gaining more attention within policy decisions on urban transformations. In this context, Decision-Makers (DMs) need evaluation methodologies able to support the definition of policies and actions for the future of cities, that focus on a higher degree of life quality and new needs. In this paper, an integrated framework is proposed which combines the Stakeholder Analysis, the STEEP and SWOT analyses (STEEP + SWOT), the Scenario Building and the Multicriteria Decision analysis approach (MCDA) which can be used to envision sustainable future scenarios for an underdeveloped area in Northern Italy. The adoption of integrated methodologies facilitates the analysis of each phase of the decision problem, from its early stage to the selection of the most suitable scenario according to the context and the stakeholders engaged. With this perspective, the present research is a guiding tool for DMs for the design of transformation/regeneration scenarios with a long-term perspective of sustainable cities and neighbourhoods. From the results obtained, it is possible to build new and unexpected scenarios by combining the main opportunities and strengths of most suitable alternatives.
10. A robust metamodel-based optimization design method for improving pedestrian wind comfort in an infill development project
Sustainable Cities and Society, Available online 15 May 2021, 103018
Constructing a new building inevitably modifies the microclimate in its vicinity. We propose a metamodel-based optimization method to devise optimal designs that minimize building’s adverse impacts on nearby pedestrians’ wind comfort in hot and cold seasons. Four design parameters, i.e., building width, building depth, building height, and building orientation, are considered for a greatly simplified building design task. Specifically, computational fluid dynamics (CFD) analyses are performed to calculate the mean wind velocity, while all CFD experiment samples are determined through the Box-Behnken design of experiment method. Based on 54 CFD experiments, the relationships between building design variables and the summer and winter mean velocities within a specified assessment area are learned using the response surface methodology. Finally, the desirability function and a genetic algorithm are combined to identify optimum design options under the robustness control (i.e., family error rate λ) for response surface models. The framework is applied to an infill development project to highlight its suitability in a real application. The experiment results show that as λ gradually decreases from 1 to 0.05, the overall desirability index dwindles from 0.33 and 0.22, consequently generating a more conservative optimum design decision.
11. Developing a place-sensitive tool for park-safety management experiences from green-space managers and female park users in Oslo
Urban Forestry & Urban Greening, Volume 60, May 2021, 127057
Fear of crime may restrict people’s use of urban green spaces and thus decrease those spaces’ potential public health benefits. Managerial measures in public green spaces that enhance perceived safety are therefore necessary. However, park managemnet in the Nordic countries seems to lack the knowledge and practice of assessing park users’ perceptions of safety. The objective of this paper was to develop a place-sensitive tool for park safety–management practice that combined park manager and user perspectives adapted to the Nordic context. Two empirical studies were conducted in Oslo to achieve this objective. Phase 1 included a focus-group interview with a team of municipal green-space managers to investigate challenges in their safety-related work. In phase 2 a multi-method field study was conducted in an urban park to assess female user’s perceptions of safety in a place-sensitive manner and test methods to be included in a tool for managers. First, safety walks and interviews with ten female residents provided on-site information on how their local park was perceived in terms of safety. The walks also resulted in identification of problematic places. These places were then systematically assessed by twenty female non-residents using questionnaires exploring the relation between perceived environmental attributes and perceived safety. Based on the green-space managers’ experiences and addressed needs, as well as experinces from the field study, a place-sensitive method and accompanying tool—called SAFE—for assessing perceived safety in urban parks for managerial purposes is presented.
12. A surrogate-assisted optimization framework for microclimate-sensitive urban design practice
Building and Environment, Volume 195, 15 May 2021, 107661
Simulations can often benefit microclimate-sensitive urban design by offering insightful Abstract:ions of stochastic urban system behaviors, yet many of them are difficult to use and generally consume significant computational resources. We adapt an advanced surrogate-assisted evolutionary optimization algorithm instead of other empirical multi-objective evolutionary algorithms commonly used to search for optimal design alternatives to confront the challenge. Moreover, a parametric design module is hybridized with this surrogate-assisted evolutionary optimization algorithm to create a working scheme for mathematically modeling microclimate-sensitive urban design problems. This seven-step scheme is tested using a hypothetical case, a spatial planning problem in a residential block, to search for design proposals that maximize project development profits and facilitate the needed creation of a comfortable wind environment. Moreover, by utilizing three optimization solvers, we obtained a near-optimal site plan with a wind velocity ratio of 0.36, a wind velocity Gini index of 0.31, and a gross profit of 4.05 × 108 RMB. Also, the case study results show that the proposed optimization framework, which consists of a global surrogate (additive Gaussian process model) and a local surrogate (gradient boosted regression trees model), converges faster and provides better optimal solutions to a high-dimensional design problem compared to the algorithm which only uses a single surrogate. Built with a flexible structure, we believe the proposed framework can address the emerging demands for a wide range of microclimate-sensitive design tasks, especially those with costly simulations and small experimental datasets.
13. The effects of lateral entrainment on pollutant dispersion inside a street canyon and the corresponding optimal urban design strategies
Building and Environment, Volume 195, 15 May 2021, 107740
Intensive traffic emissions have caused many environmental problems and have a negative effect on public health. With the aim of mitigating these problems, it is essential to figure out how the flow structure affects the pollutant dispersion within the urban canopy. Most previous studies focus on the canopy vortex caused by top entrainment, but few previous studies are aware of the importance of lateral entrainment. By conducting computational fluid dynamic (CFD) simulations validated by wind tunnel data, we investigate the effects of lateral entrainment on pollutant dispersion inside a street canyon. Eight three-dimensional street canyons with various building heights and street lengths are considered. Besides, three optimal design strategies are proposed to improve the air quality by enhancing the lateral entrainment. The results of this analysis demonstrate that lateral entrainment could conditionally reduce the pollutant concentration of low-rise canyons. This reduction, which is affected by lateral entrainment, is confined in a range of approximately 2.5 times the street width from the street ends. In contrast, the lateral entrainment causes a more pronounced reduction in the pollutant concentrations of the high-rise canyons. Besides, all three strategies can considerably facilitate the lateral entrainment, leading to a significant reduction in the cross-section pollutant concentrations (by up to 76%) and therefore a significant reduction in the personal intake fraction P_IF of the residents (by up to 81%).
14. Beyond neoliberal urbanism: Assembling fluid gentrification through informal housing upgrading programs in Shenzhen, China
Cities, Volume 112, May 2021, 103111
Over the past decade, Chinese metropolitan cities, Shenzhen included, have waged large-scale gentrification campaigns through land appropriation and demolition of old neighborhoods, resulting in the financialization of the urban property market. Since 2018, however, a new gentrification scheme under the rubric “comprehensive improvement” has been introduced in Shenzhen, in which the rehabilitation and formalization of informal housing arrangements in urban villages, instead of sweeping demolition, have become the focus. Based on fieldwork in a migrant community experiencing gentrification, I argue that the new gentrification scheme is fluid in the sense that, first, it comprises an assemblage of heterogenous actors, socialist institutions, market mechanisms, and a development regime. Even though the relationships between these components are not stable, this assemblage of factors enables the state to maintain some degree of power that it uses to regulate and channel the capital involved in the scheme. Second, gentrification is not a coherent process driven by a single force inevitably towards neoliberalism. Rather, it serves multiple purposes. Other than capital accumulation, fluid gentrification also functions as infrastructure for incorporating young professionals into state-led development. Fluid gentrification therefore goes beyond neoliberalism, pioneering a post-industrial mode of urban regeneration that is unstable, temporal and flexible in nature.
15. Spatial, infrastructural and consumer characteristics underlying spatial variability in residential energy and water consumption in Amsterdam
Sustainable Cities and Society, Available online 1 May 2021, 102977
To design effective strategies for sustainable urban resource management, it is essential to understand which urban characteristics underlie consumption patterns. We used multiple linear regression analyses to examine sixteen factors on their explanatory power for spatial variation in residential electricity, gas and water consumption in Amsterdam. Four models per resource were used, based on distinct spatial units aggregating high-resolution data: neighbourhoods, districts, 100 m squares and 500 m squares. We found twelve explanatory variables for spatial variability in consumption in total and nine or ten per resource. The number and relative importance of explanatory variables varies with the spatial units used. Overall, neighbourhood models explain variance in consumption data best (adjusted R² = 0.88, 0.86, 0.74). Income level and building type stand out for having high relative importance (top 4) in all four models for two of the three resources; migration history shows an important correlation with water consumption, which was not described hitherto. We conclude that explanatory variables for resource consumption are sensitive to size and shape of spatial units used. We recommend to use future high resolution studies for different resources of interest to determine which spatial and temporal resolutions of analysis can support urban planners and designers in formulating context-specific interventions.
16. Case comparison of typical transit-oriented-development stations in Tokyo district in the context of sustainability: Spatial visualization analysis based on FAHP and GIS
Sustainable Cities and Society, Volume 68, May 2021, 102788
Sustainability in transportation development has been a fixture in recent discourse. TODness is a principle that evaluates the extent to which sites meet Traffic-Oriented Development (TOD). To an extent, it reflects some criteria for sustainable transportation development. Based on the TODness, this paper develops a comprehensive index called “Sustainable TODness” around the four dimensions of sustainable development—environmental, economic, social, and transportation efficiency—combined with the Fuzzy Analytic Hierarchy Process. Using this index, an evaluation of 13 TOD stations in the Tokyo metropolitan area was carried out, and the impedance pedestrian catchment area of each station was spatially analyzed in conjunction with the geographic information system to generate a heat map of indicators’ distribution. According to the spatial characteristics reflected by the heat map, the stations are divided into three categories. We found that some popular TOD stations have high scores on the economic level, but have more or fewer deficiencies in the other three dimensions. We believe that the research method in this article is applicable to the sustainability evaluation of any TOD site in the world and provides new ideas for the renewal of developed urban areas and new land use in the future.
17. Citizen engagement body of knowledge – A fuzzy decision maker for index-term selection in built environment projects
Cities, Volume 112, May 2021, 103137
Contribution of citizens is a key factor in the success of urban development projects and the cornerstone of smart cities in general. The domain researchers have attempted to understand the attributes of a meaningful and effective collaboration with citizens and improve the quality of engagement accordingly. With this aim, a rich and extensive literature has been created, covering different aspects of citizen engagement. The subjective-ness and context-sensitivity of involved issues, however, do not allow for a ‘universal’ standard solution to be proposed, even to a similar problem, in different spatiotemporal contexts. In this paper, after an extensive analysis of a broadly inclusive range of existing literature through more than 1092 publications, a conceptual framework is proposed to contextualize citizen engagement in urban projects. Using this framework, a model is trained, with the aid of the fuzzy paradigm to provide fuzzy sets of most relevant keywords for a query regarding citizen engagement in urban projects, and a decision support system is developed to retrieve the most relevant publications, based on the fuzzy inference mechanism. The system provides the most relevant keywords for reviewing the literature, as well as the most related documents, through answering a set of simple questions. The solution is deployed through a user interface, linked to the well-known Elsevier online database Scopus. The developed system can assist researchers and practitioners with retrieving knowledge from the literature, for setting up new projects.
18. Urban ecological security assessment and forecasting using integrated DEMATEL-ANP and CA-Markov models: A case study on Kolkata Metropolitan Area, India
Sustainable Cities and Society, Volume 68, May 2021, 102773
Due to rapid urbanization, Indian cities have faced serious environmental problems, including pollution, loss of urban green space, increasing heat island phenomena, and destruction of the urban ecosystem, over the past few decades. Urban ecological security (UES) measures the degree of urbanization pressure and level of ecological sensitivity. Currently, urban ecological security assessment (UESA) is an important aspect of sustainable urban development. Accurate assessment of ecological security status has become a real problem because of differential evaluation methods produced variable results. The present study aims to address these shortcomings using integrated DEMATEL-ANP model to select the influencing factors and assess ecological security of Kolkata Metropolitan Area (KMA). Moreover, a combined cellular automata and Markov chain model was applied to simulate land-use/land-cover change and predict the future state of UES in KMA. The result shows that land use land cover change rate, built-up density, green area change intensity index and landscape connectivity index are the most influencing factors in UES. The present study can enrich the methods in the field of UESA and the findings of this study can provide valuable and scientific guidance to optimize land-use planning and potentially improving the ecological security of an urban area.
19. Rethinking urban heat stress: Assessing risk and adaptation options across socioeconomic groups in Bonn, Germany
Urban Climate, Volume 37, May 2021, 100857
With climate change and socioeconomic trends expected to exacerbate the risk of urban heat stress, implementing adaptation measures is paramount to limit adverse impacts of heat on urban inhabitants. Identification of the best options needs to be based on sound, localised assessments of risk, understood as the interaction of hazard, exposure and vulnerability. Yet a review of the literature reveals that minimal research to date considers the perceived impacts of heat among urban residents. Based on a household survey in Bonn, Germany, this paper adopts an integrated approach to assess how different socioeconomic groups are affected by heat stress and explores the connections between perceived impacts of heat and indicators of exposure and vulnerability across groups. Results indicate that all socioeconomic groups are at risk of urban heat stress, though to differing extents and for different reasons. Exposure was found to be lowest in groups typically considered to be of higher risk, such as older respondents, who at the same time have the highest susceptibility. Students and other younger respondents, on the other hand, face comparably high exposure and have the lowest coping and adaptive capacities. At the same time, each group has its own capacities with the potential to mitigate risk. The study shows that urban inhabitants beyond “classic risk groups” usually addressed in literature and policy are affected by heat stress in ways that may not be accounted for in current urban policy.
20. Non-linear relationship between urbanization paths and CO2 emissions: A case of South, South-East and East Asian economies
Urban Climate, Volume 37, May 2021, 100814
This study investigates the non-linear relationship between urbanization paths and CO2 emissions in selected South, South-East, and East Asian countries over the period 1971–2014. Based on the STIRPAT (Stochastic Impacts by Regression on Population, Affluence, and Technology) framework, we applied the advanced and robust methods of dynamic seemingly unrelated regression (DSUR), dynamic OLS (DOLS), and fully modified OLS (FMOLS) to estimate the long-term effects. The empirical findings revealed the inverted U-shaped effects of urbanization and urban agglomeration and the U-shaped impact of the largest city ratio on CO2 emissions. Urbanization and urban agglomerations improve environmental quality in the long-run and support ecological modernization theory. However, excessive concentration in the largest cities have severely affected the environmental quality and violates the notion of compact-city efficiencies. Moreover, energy intensity and economic growth positively affect CO2 emissions, while trade openness negatively influences CO2 emissions. Our robustness analysis at the country-level applies the augmented mean group (AMG) panel ARDL technique, which further supports the non-linear effect of urbanization paths on CO2 emissions except for a few countries. The results of the panel Granger non-causality approach unveil bidirectional causality of energy efficiency, economic growth, urbanization, and largest city ratio with CO2 emissions. In contrast, unidirectional causality runs from urban agglomeration to CO2 emissions. Our findings have important policy implications as we suggest green urban infrastructures, eco-friendly dwellings, smart cities, country-specific trade policies, and renewable energy options to improve the environmental quality.
KHOA HỌC VÀ CÔNG NGHỆ TRONG LĨNH VỰC XÂY DỰNG
1. The recent residential apartment buildings’ thermal performance under the combined effect of the global and the local warming
Energy and Buildings, Volume 238, 1 May 2021, 110828
Both global and local heating phenomena can potentially influence the building thermal performance and comfort. The residential construction sector had a real estate “boom” in the beginning of the 2000’s in Sao Paulo and there is no available information on how this recent built stock performs under the current climate and how it will do, considering the warming climate. Therefore, this study addresses the real estate residential apartment buildings developed in the 2000’s, aiming to investigate their thermal performance and expected comfort conditions, considering the urban present and future climate. The average air temperature difference (ΔT) between the high-rise dense urban area and the suburban stations was registered and then coupled to the future weather file. Comparing the apartment’s thermal performance under the base weather file (SWERA) and the Future (2045–2074) + UHI, in yearly values, an important decrease in comfort hours (from 81% to 65%) was found, while in a hot period (February) the results are much more critical (64% heat discomfort hours). It is important to address how central is the adaptability for improving the domestic comfort conditions, especially in the pandemic and post pandemic scenarios, when people are expected to spend more time inside their homes.
2. Structural design of a sustainable house with energy and water efficiency
Materialstoday, Available online 8 May 2021
This research aimed to develop a prototype of sustainable housing for the Latin American and Caribbean region, specifically for Pucallpa City, which is located in the Peruvian Jungle. A structural design Truss and Column was proposed, made up of Capirona wood as the main construction material, while for the covering of the walls housing, the construction of modular panels was carried out using low carbon footprint materials, such as Bamboo. Besides, the design of an Artificial Wetland was presented to optimize the use of natural resources such as treated water. Finally, the energetic feasibility of an On-Grid Photovoltaic system was evaluated using the PVsyst software. The main results of the structural design showed that the elements such as beam, joist, and column do not exceed what is admissible, complying with Peruvian Technical Standard E010. The Artificial Wetland achieved removal efficiencies of 96.27% turbidity and 98.6% Biochemical Oxygen Demand (BOD). The Photovoltaic system showed a performance ratio of 0.767, with low losses by temperature (11.29%) and ohmic wiring (1.15%), achieving to avoid the emission of 16.1 tons of carbon dioxide in a lifetime of 30 years. Through this project, we are modeling the constructive customs of the jungle residents and providing an innovative solution for sustainable housing with energy and water efficiency for dense and urban areas of the Peruvian Amazon.
3. Brickwork wall models strengthened with diagonal and horizontal GFRP strips
Composite Structures, Available online 6 May 2021, 114062
The use of fiber reinforced polymers (FRPs) as external bonded (EB) strengthening of unreinforced brickwork masonry has became a common intervention technique for restoration of masonry walls damaged by seismic actions with the aim to improve the capacity under in-plane shear loading. The exact knowledge of the behavior of system composed by masonry and EB FRP strips through the interaction mechanism between strengthening and substrate is essential for the effectiveness of interventions based on the use of FRP strips. This paper provides an investigation on the behaviour of unreinforced and reinforced masonry walls made with solid clay bricks in scale 1/3rd, considering the presence of different types of masonry, such as historic and modern, and different configuration of the GFRP strengthening. Three walls, characterized by double T shape, were tested under combined compression and shear loading. Two of them were strengthened after damage using, respectively, diagonal and horizontal EB GFRP strips; another one was strengthened with horizontal GFRP strips without damage and subjected to the same loading path until failure. The response of all models is illustrated and discussed considering the walls’ shear strength and effects on the failure mechanism due to diagonal and horizontal EB GFRP strips.
4. Construction type influences features of rising damp of blue-brick masonry walls
Construction and Building Materials, Volume 284, 17 May 2021, 122791
The occurrence of rising damp in historical buildings results in material deterioration, energy waste, water-related damage, uncomfortable indoor air, and mould growth. The rising process in a real wall is influenced by the construction types, masonry details, environmental conditions, physical properties of brick and mortar. To clarify the features of rising damp influenced by the construction types in blue-brick masonry walls, a solid wall and a cavity wall made of clay blue bricks and lime mortar with a size of 3 m (high) × 1.2 m (wide) × 0.24 m (thick) were constructed to perform a water rising experiment for 600 days in a closed laboratory. The results demonstrated that the construction types directly affected the rising speed and the height of sharp fronts, which were 192 cm in the cavity wall and 168 cm in the solid wall after 600 days. The calculation model of the moisture rising in the solid wall and cavity wall obeyed the sharp front model of a homogeneous wall; however, the environmental conditions affect the rise of sharp front and moisture distribution. The research expands the understanding of the rising damp in real masonry and provides data supporting the moisture simulation, energy consumption, and heritage conservation of brick masonry.
5.Damage evaluation of sandwich material on side plate hull using experimental modal analysis
Materialstoday, Available online 10 May 2021
Sandwich material is a material innovation that is applied widely. One example is the sandwich material in ship construction. The application of the sandwich material provides the advantages of reduced weight and toughness under impact loads. In the development of this material can be damaged. The majority of damage that occurred in the core of the material was hard to identify. In this study, the identification of damage evaluates by testing the sandwich material on a laboratory scale. The damage was evaluated by experiments modal analysis (EMA). This technique uses a vibration base to determine damage to the material. Damage indicators detect when there is a natural frequency decrease in the frequency of the sandwich material.
6. Experimental investigation on the in-plane seismic performance of damaged masonry walls repaired with grout-injected ferrocement overlay
Construction and Building Materials, Volume 282, 3 May 2021, 122565
This experimental study compares two scaled unreinforced masonry (URM) walls before and after being repaired by grout-injected ferrocement overlay reinforcement (GFOR), with the aim of investigating the effectiveness of an alternative ferrocement overlay technique. In the experiment, loading was performed on a multistory opening URM wall to induce damages, and the reinforced wall (defined as FRM) was retested using the same procedure. A comparative analysis of the seismic performances of the two walls in terms of failure modes, bearing capacity, hysteresis curve, energy dissipation capacity, and deformation behaviors was performed. The experimental results indicated the following. (i) The application of GFOR on the damaged URM wall altered its diagonal shear failure into the flexural-dominant mode. (ii) The ultimate resistance and residual strength of FRM increased by 6% and 13%, respectively, compared with those of URM. (iii) The ultimate and residual deformations of FRM increased by 110% and 60%, respectively, compared with those of the URM. (iv) The ductility of the overall walls improved from 2.48 to 2.72. This study verified the reasonability and effectiveness of the application of GFOR to damaged masonry structures.
7. Cumulative Deformation Capacity of Structural Steel Subjected to Extremely Large Amplitude Strain Histories
Journal of Building Engineering, Available online 11 May 2021, 102649
This study investigated deformation behavior of structural steel subjected to large strain. When structures experience powerful earthquakes, strain amplitudes at the fracture locations can be quite large, and the material fractures after few loading cycles. The Manson-Coffin relationship is commonly used to predict failure of metals subjected to cyclic loadings. However, the traditional Manson–Coffin relationship does not necessarily hold for some materials under extremely large strain amplitude. There are few relevant experiments, largely because it is difficult to reproduce structural steel behavior under large amplitude cyclic stains in the laboratory due to buckling. In this study, 71 steel plate specimens of structural steel were loaded until fracture under diverse cyclic axial strain loadings and monotonic tension. The relationship between cumulative strain and its skeleton portion was obtained based on the analysis of the hysteresis loops. Due to the limitation of test setup, the largest compression strain amplitude is 6%, which is still not sufficient to study the material behavior of structural steel under severe earthquakes. Therefore, numerical simulations of single steel elements subjected to cyclic strain were conducted to complement the material behavior under extremely large constant strain amplitudes. The cumulative deformation capacity of structural steel subjected to extremely large strain amplitudes was evaluated through a strain-life curve with the experimental and analytical results. In the final part of this study, experimental results from former research were introduced to validate the proposed strain-life curve.
8. Non-destructive testing and Finite Element Method integrated procedure for heritage diagnosis: The Seville Cathedral case study
Journal of Building Engineering, Volume 37, May 2021, 102134
One of the major problems faced by historic cities today involves the conservation of heritage buildings. Damage suffered by these buildings can be irreversible and fast-acting, leading to their disappearance over a short period. The study and analysis of the origin of the damage suffered by these buildings have proved themselves to be key to their conservation. Non-destructive testing (NDT) can detect problems indiscernible to the naked eye, thereby preventing potential losses. In this paper, a non-invasive method for the diagnosis of building structures integrated with the Finite Element Method (FEM) was applied to the Tabernacle Chapel; a building included in the northwest wing of the Cathedral of Seville complex. Despite the many interventions carried out to date, the issue of the chapel’s deterioration has yet to be entirely solved. This research describes the results of a detailed constructive and structural diagnosis methodology for heritage buildings. The data provided from NDT methods, such as Digital Image Processing (DIP), Infrared Thermography (IRT), Laser Levelling (LL), Ambient Vibration Testing (AVT), and Ground-Penetrating Radar (GPR), has been verified and integrated as boundary conditions in a 3D Finite Element Method (FEM) in order to establish the critical points of the structure, including the failure mechanisms. The results led to the conclusion that the main causes of deterioration involved the settling of the grandstand built in the northwest sector of the building and the effects of the thrusts of the dome on the lateral façades. An integrated implementation methodology of NDT and FEM has enabled accurate knowledge to be ascertained of the principal damage affecting this heritage building.
9. Seismic performance of angle steel frame confined concrete columns: Experiments and FEA model
Engineering Structures, Volume 235, 15 May 2021, 111983
Angle steel frame confined concrete columns (ASFCs) are an improved form of steel-jacketed concrete composite columns. An ASFC consists of an concrete column and an inner angle steel frame (ASF). The ASF offers two advantages: confining core concrete and improving seismic performance. The existing studies have been limited on seismic performance of ASFCs. This paper presents experimental and numerical studies on seismic performance of ASFCs. The experimental program included the lateral quasi-static cyclic tests of eight specimens, with the main variables being the axial compression ratio, the section form and the assembly of steel batten. The numerical program included establishment process of numerical models in finite element analysis software (OpenSees), and the expanding analysis on influence factors of ASFCs. The experimental results showed that all ASFCs have high bearing capacity, high ductility and full hysteretic curve. The numerical model could provide reasonably accurate prediction of experimental results. The factor analysis showed that axial compression ratio and steel content of angle steel are two main factors for seismic factors, and the confining effect exerts great influence on dividing axial compression ratio.
10. Progressive collapse of RC flat slab substructures with unbonded posttensioning strands after the loss of an exterior column
Engineering Structures, Volume 234, 1 May 2021, 111989
Reinforced Concrete (RC) flat slab structures are mainly composed of load-bearing columns and RC slabs, which are vulnerable to collapse once one or several local load-bearing columns fail due to accidental loads such as terrorist bomb attack or vehicle collision. To investigate the progressive collapse performance of flat slab structures after the loss of an exterior column, static collapse tests were conducted on three 1 × 2 bay RC flat slab substructures. Effect of prestress and layout of the unbonded posttensioning strands (UPSs) on the progressive collapse of flat slab structures was discussed. Experimental results showed that punching shear failure (PSF) foremost occurred at the slab-column connection (SCC) of the failed exterior column during collapse, and then successively occurred at the SCCs close to the corner column and the exterior column adjacent to the failed column. Primary cracks on the top slab surfaces around the failed exterior column generally presented arc-shaped distribution; while primary cracks on the bottom slab surfaces radially propagated from the failed exterior column. Comparing with the flat slab substructure without UPSs in the slabs, the load-bearing capacity of the substructures with UPSs in the slabs significantly improved. Flexural action was the fundamental collapse resistance mechanism in the initial collapse stage, and tensile membrane action gradually formed during collapse. The flexural action, the tensile membrane action, as well as the post-punching behaviors of the slabs resisted the collapse load together before the final collapse occurred. Most of the load applied on the failed exterior column mainly transmitted along the shorter slab bay under the exterior-column-removal scenario. Arranging posttensioning strands in the slabs contributed to reducing vertical deformation of the slabs. The UPSs in the column strip passing through the failed column played a more important role in resisting collapse load than those arranged in the middle strip. The residual flat slab substructures still possessed satisfactory load-carrying capacity even if PSF occurred in one or several SCCs.
11. A review of the circularity gap in the construction industry through scientometric analysis
Journal of Cleaner Production, Volume 298, 20 May 2021, 126870
The circular economy (CE) concept has gained popularity among scholars and practitioners as the best way to circumvent the effects of the linear economy and create an effective platform to attain sustainable development within industries including the construction industry. However, understanding parameters of the knowledge body and key issues which needs to be harnessed to enhance the application of concept to the construction industry has been a challenge. In this study, a scientometric analysis was employed to analyze 486 bibliometrics-searched filtered articles of CE in the construction industry to provide a critical understanding of current research trends and applications. Content analysis of selected articles were provided to elucidate key findings, challenges, and proposed strategies, and a SWOT analysis was conducted to appraise the incidental results of applying various circularity strategies to the construction industry. The study has found that key influential areas such as circular product design, end-of-life consideration including the quality, economics, and modular integrated construction were narrowly covered in existing studies. Moreover, there is still a lack of practical CE approach which can integrate the holistic performance assessment tool with the circular business model for the construction industry. Based on the circularity gaps identified through the content analysis, a research framework which consists of eight different research themes including the circular design; manufacture and supply; strategies for CE adoption; consideration of end-of-life principle; CE outcomes/consequences; information exchanges; construction process; and waste management strategies is developed. In addition, a compressive methodological framework is proposed for the effective CE implementation and evaluation. The circularity gaps, key influential areas, research themes, and CE approach highlighted in this study can be used as a guide for future scholarly work and practical adoption of CE in the construction industry.
12. Comparative assessments for environmental impacts from three advanced asphalt pavement construction cases
Journal of Cleaner Production, Volume 297, 15 May 2021, 126659
Applying advanced asphalt pavement technology is a promising trend for future sustainable road construction. However, the environmental impacts of different advanced asphalt pavements remain unclear, thus hindering their future applications. This study presents comparative assessments for the energy consumption and Greenhouse Gas (GHG) emission of advanced asphalt pavement constructions in light of life cycle assessment (LCA), taking three selected cases as representatives for self-healing, steel slag recycling and warm mix technology. A holistic inventory for material and machinery is compiled based on the primary data from construction sites. Afterwards, the environmental assessments of three advanced asphalt pavements are compared from the upper and the overall asphalt layers perspectives, respectively. In addition, the critical sectors during pavement construction are identified based on comparative analysis. The results show that considering the single upper layer, the construction of 1 km self-healing layer causes the most of environmental burdens at 139.51 metric tons of CO2 equivalent and 1.81 TJ of energy consumption; steel slag recycled layer causes the lightest, approximately 60% of self-healing layer’s consequences. From the overall asphalt layers perspective, constructing warm mix asphalt pavement is the most environmentally friendly which generates 238.74 metric tons of CO2 equivalent and 3.59 TJ of energy consumption for 1 km. The environmental burdens generated in materials extraction stage occupy considerable percentage with 47.41%–71.29% of CO2 equivalent and 55.08%–73.68% of energy consumption. Recycled materials applications, transport distance managements and located climate conditions are three identified aspects of strikingly affecting environmental impacts of asphalt pavement construction.
13. Estimation of resilient modulus of cement-treated construction and demolition waste with performance-related properties
Construction and Building Materials, Volume 283, 10 May 2021, 122107
Construction and demolition (C&D) waste is generated for 100 billion tonnes per annum globally, which has caused underground water contamination and farmland occupation when disposing the C&D waste by landfilling. The C&D waste materials have been recycled and used as an alternative to virgin mineral aggregates in pavement construction. This study aims at proposing a convenient method to estimate resilient modulus of cement-treated C&D waste materials when used in pavement base layer based on material performance-related properties and using discrete element simulation tests. Two kinds of materials are investigated, they’re blends of two C&D waste materials, crushed bricks (CB) and recycled concrete aggregate (RCA). Fundamental property experiments were carried out on the aggregates to evaluate the engineering performance. Unconfined compress strength (UCS) tests were conducted on cement-treated materials to analyze the effect of curing duration and cement content on UCS. The numerical resilient modulus (Mr) tests by the discrete element method (DEM) were conducted to evaluate the resilient performance of C&D waste. The simulation results were verified with the lab measurements. Test results showed that the test materials have a high water absorption and a low durability. The minimum cement content was determined as 5% to satisfy the strength requirement of 4 MPa according to the national standards. Mr increases with confining pressure. Performance-related properties (UCS, γd, E50) were proposed to build their correlations with k values of the resilient modulus model, which are formulated to predict the k values. The values of Mr predicted by the performance-relatedproperties were consistent to the DEM modeled ones.
14. Covalently construction of poly(hexamethylene biguanide) as high-efficiency antibacterial coating for silicone rubber
Chemical Engineering Journal, Volume 412, 15 May 2021, 128707
Biofilm formation on biomedical devices & implants and the resulting bacterial induced infections are remaining severe clinic issues. Here, a facile layer-by-layer strategy to covalently construct poly(hexamethylene biguanide) (PHMB) as the high-efficiency bactericidal coating on silicone rubber (SR) has been developed. Based on the NHS/NH2 chemistry (the reaction between active ester groups and amino groups), an active ester homo-polymers (pNHSMA) as the precursor layer was created on activated SR surface (SR-NH2), which followed by the immobilization of dense PHMB coating. XPS and water contact angle tests verified the successful construction of PHMB coating on the surface. Robust relationships between the contact time/initial seeding density of bacteria and the bactericidal capacity of the coating have been established based on systematical qualitative and quantitative antibacterial evaluations. Results showed that the PHMB coating is able to kill 100% of the attached S. aureus cells within 1 h with initial density below 1.18 × 105 CFU/cm2 without compromising of the cytocompatibility of the substrates. Interestingly, the coating significantly increased the mechanical property of the SR substrates due to the additional crosslinking introduced by the coating. Furthermore, the high-efficiency antibacterial property of PHMB coating (bactericidal ratio of 96.83%) and the significant suppressed implant-induced infection have been verified via the in vivo simulated infection model on rats. In the meantime, this surface modification strategy can be easily applied to SR based catheters, which is able to completely kill the surface attached bacteria when immersed in a bacterial suspension with a density of 3 × 106 CFU/mL for 30 min. These findings provide a new approach to combat the biofilm formation and devices-associated infections for general SR based biomedical devices/implants.
15. Preparation and characterization of high-strength and water-resistant waterborne epoxy resin/magnesium oxychloride composite based on cross-linked network structure
Construction and Building Materials, Volume 285, 24 May 2021, 122902
To expand the application of magnesium oxychloride cement (MOC) as a kind of engineering materials in the construction field, organic–inorganic hybrid modifications were performed. Waterborne epoxy resin/magnesium oxychloride composites (WER/MOC) with high-strength and water-resistance were prepared using a simple and green method with MOC as matrix and WER as reinforcement. The effects of WER on the resulting composite’s viscosity, mechanical strength, water resistance, phase composition, thermal stability, and micromorphology were discussed. The results demonstrated that WER reduced the viscosity of the WER/MOC complex system, and the composite water resistance and compressive strength were improved, which were mainly attributed to chemical reactions between WER and MOC to form a crosslinked network structure. Meanwhile, XRD analysis results showed that the intensity of the diffraction peak of the 3-phase decreased and 5-phase increased with WER addition to the composite and no new crystal phase appeared. The compressive strength, water resistance, thermal stability, and porosity of these WER/MOC composites reached the best values when the WER mass proportion was 4.8%. Here, the composite water absorption rate decreased to 8.7%, softening coefficient increased to 17.8%, middle compressive strength (sealed for 7 d) at 48.0 MPa, and dry bulk density increased to 1.34 g/cm3. Thus, these WER/MOC composites were suitable for use as engineering materials in the construction and road industries.
16. Sustainable construction and demolition waste management in Somaliland: Regulatory barriers lead to technical and environmental barriers
Journal of Cleaner Production, Volume 297, 15 May 2021, 126717
The large amount of construction and demolition waste (CDW), coupled with poor management create burdens for the environment, society and economy. Barriers hinder sustainable CDW management. Understanding the barriers can promote the development of eco-friendly, socially harmless, and economically viable strategies. This study aims to integrate sustainable waste management in construction (SWM) and demolition practices. This study develops a valid set of attributes to justify the interrelationships among the barriers. The attributes of sustainable waste management are qualitative by nature, and uncertainties exist because of linguistic preferences regarding the attributes. This study applies the fuzzy Delphi method to validate five barriers and 14 criteria under uncertainties. Fuzzy decision-making trial and evaluation laboratory (DEMATEL) with qualitative information is used to determine the interrelationships among the barriers. The results indicate that regulatory barriers are the primary cause of technical and environmental barriers. In Somaliland, the criteria hindering sustainable CDW management practices are the lack of awareness, the lack of commitment, ineffective management, the lack of collaboration, the lack of national vision, inadequate funding, limited infrastructure, the lack of supervision, and the lack of legal enforcement. The theoretical and managerial implications of this study are discussed.
17. Abating heat waves in a coastal Mediterranean city: What can cool roofs and vegetation contribute?
Urban Climate, Volume 37, May 2021, 100863
The frequency and intensity of heat waves (HW) in cities are on the rise due to climate change as well as urban fabric materials and anthropogenic activities that affect heat accumulation. The efficacy of HW mitigation strategies depends on a city’s specific and unique morphology, land use, building materials, climate and geography. In this study, we show the effectiveness of cool roofs and vegetation in reducing temperature in the Metropolitan Area of Barcelona (AMB). We use the Weather and Research Forecasting (WRF) model with the urban scheme BEP+BEM, including11 urban classes to simulate a HW that occurred in August 2015. We find that cool roofs reduce temperature best during the day (0.67 °C average and 2.22 °C maximum reductions), while additional green areas moderate temperatures to a lesser degree but also more evenly during the day and at night (average reductions of 0.15 °C and 0.17 °C, respectively). However, when irrigation is increased, the temperature reduction during the day is intensified due to the cooling effect of more evapotranspiration. The thermal regulation of combining the two strategies is the most evenly distributed over the AMB and has the highest impact, with an average and maximum reduction of 1.26 °C and 4.73 °C at 13:00UTC.
18. New step-by-step retrofitting model for delivering optimum timing
Applied Energy, Volume 290, 15 May 2021, 116714
Although the Energy Performance of Buildings Directive 2018/844/EU introduced the building renovation passport and by such proposed to consider step-by-step renovation, a literature review could not identify any explicit step-by-step retrofitting optimisation model. Therefore, the present study seeks to explore the following research questions: which indications regarding the optimum timing of renovation steps can a net present value maximising model deliver; how are model’s results impacted by the interdependency of renovation steps and by homeowner’s budget restrictions. The model relies on three pillars: homeowners’ budget restrictions; building material ageing processes; and interdependency between the retrofitting steps. Implemented as a mixed-integer linear program, it maximises the net present value of households’ energy-related cash flows, and delivers the optimum timing when each step should be performed. As input data, five real-life building renovation roadmaps were used. The appropriate metric to assess building’s retrofitting energy savings is also discussed. When comparing both single-step and step-by-step approaches, the step-by-step presented 11–22% higher cumulated energy savings. Results also show that a renovation period would last between 1 and 14 years and 2 to 11 years, depending on whether interdependency of measures is considered. This has direct implications on the improvement of building stocks’ energy efficiency, and consequently, the achievement of decarbonisation targets set for 2050. In this context, the model delivers a more concrete time horizon perspective in regards to the achievement of these targets. Future work will include quantifying the economic effects of interdependency of steps and expanding the analysis for varies techno-economic building typologies.
19. Optimization of drilling process parameters of AA7150/MoO3 composites using Taguchi method
Materialstodya, Available online 15 May 2021
Aluminum 7150 has established a wide variety of uses in aerospace, industrial, architectural manufacturers, frames, tubes and pipes due to its unique properties and the Mechanical properties of aluminum alloy 7150 composites (AMCs) reinforced with 40-µm molybdenum-trioxide particles were examined in this work. This experimental work was highly focused on optimized the surface roughness analysis of AA7150 – Molybdenum Trioxide (MoO3) AMCs with three machining variables. The superior strength AA7150 alloy is perceived for this function and boosts the strength by strengthening MoO3 particles with various mass proportions. The AA7150/MoO3 AMCs are manufactured via the melt stir casting method. The optimization of the drilling variables for this analysis was regarded as drilling feed (40, 80, 120 mm/min), machining speed (800 rpm, 1200 rpm and 1600 rpm), and weight proportion of MoO3 particles (4 percent, 8 percent and 12 percent). In this process, spindle speed, feed and filler materials were used as input process variables for the drilling operation. Surface roughness was taken as the response parameters.
20. Facile fabrication of 3D TiO2 – graphene aerogel composite with enhanced adsorption and solar light-driven photocatalytic activity
Ceramics International, Volume 47, Issue 10, Part A, 15 May 2021, Pages 14290-14300
Three-dimensional (3D) titanium dioxide – graphene aerogels (TA-TiO2-GA) with network architectures and in-situ growth of TiO2 NPs onto its surface were facilely self-assembled via one-step hydrothermal treatment by employing tannic acid (TA). TA as the reducing agent and linker promoted a strong coupling between the graphene and TiO2. The TA-TiO2-GA exhibited good photocatalytic performance and reusability in the degradation of typical organic contaminants: upon 3 h simulated solar irradiation, the removal rate of tetracycline, methylene blue and rhodamine B reached 43.2%, 77.8%, and 91.9%, respectively; nearly no deactivation of the TA-TiO2-GA was observed after reuse of over10 cycles. Mechanistic studies indicated that the synergy of adsorption and photocatalysis played an important role, and superoxide radical anions and hydroxyl radicals are the major reactive oxidative species. To conclude, this study provides a novel alternative to fabricate 3D TA-TiO2-GA which has great potential in solar light-driven environmental applications.
VẬT LIỆU XÂY DỰNG
1. Cobalt ferrite: A review
Materialstoday, Available online 3 May 2021
Ferrite Cobalt (CoFe2O4) is a recognized attractive material with normal implementation and normal size of polarization. It has unmistakable substance security and motorized hardness. It is an eager promoter for the strategy of tactile gadgets and actuators, as an authoritative fixing, attractive medication gadgets electrical and having a broad scope of researching in materialistic innovation or science for mechanical uses and applications. These nanoparticles cobalt and ferrite on an ensnared viably handled on surrounding temperature by a basic process of co-precipitation. This precious stone structures and architecture of image was controlled through X-ray diffraction and SEM. The range of XRD affirms that composite nano-particles were shaped by ideal structure of spinel. This normal pace of precious stones was controlled through methods for Modified Scherer (54 nm) and Williamson-Hall (49 nm) techniques. A SEM view demonstrated nanoparticles CoFe2O4 being assembled in close-by structures. This visual and bond highlights was depicted by FTIR and UV–Vis Spectrum. As the temperature of the production rises, so does the magnetics period for the NPs and the magnetization of the concentration improves monotonously from 2.6 μB to 16 μB plus from 37 to 66 emu/g. According to the actions of both SPM and attendance of a dead layer (surface amorphous shell layer), which systemically decreases as the synthesis temperature increases, the optimum curve-appropriate of M-H statistics is due to the reduced particle/particle interaction.
2. Measurement and modelling of thermal and physical properties of wood construction materials
Construction and Building Materials, Volume 284, 17 May 2021, 122780
Construction materials exposed to fire conditions may decompose resulting in a loss of strength as well as contributing to the growth and size of the fire. Predicting the behavior of timber and other construction materials during a fire exposure requires accurate thermal modeling of the material considering both the effects of elevated temperature and material decomposition state (virgin to char) on the thermal and physical properties. This paper evaluates the use of different techniques to measure the porosity, permeability and thermal diffusivity of wood construction materials at different levels of decomposition due to a high temperature exposure. The porosity and thermal diffusivity values of wood exhibit similar changes with decomposition level. It was found that virgin and char material properties can be used in conjunction with thermogravimetric data to estimate material properties at intermediate decomposition levels. The findings can be used to reduce the number of experiments required to characterize other materials. Permeability was observed to be dependent on the structure and composition of the material. Scanning electron microscopy images revealed that decomposition increased the space between the otherwise compact-arranged elements (grain, particles), resulting in an increase in permeability. Consequently, permeability should be measured at different decomposition levels and direction to quantify the material changes due to a high temperature exposure.
3. Engineering and environmental evaluation for utilization of recycled pulp mill fly ash as binder in sustainable road construction
Journal of Cleaner Production, Volume 298, 20 May 2021, 126758
The inorganic solid waste generated in pulp and paper industries called pulp mill fly ash (PFA) is a potentially valuable resource as supplementary cementitious material. However, large PFA volume is discarded in landfills due to stringent environmental regulations and lack of proper guidelines for safe alternative applications, thereby posing substantial environmental liability. The present study investigated the effectiveness of recycled PFA as a green binder for stabilizing weak silty sand pavement subgrades by conducting a series of laboratory experiments. The important physicochemical and ecotoxicological properties of PFA indicated its valuable potential for beneficial application as an energy-efficient and low embodied carbon construction raw material. Further, the substantial soil strength and stiffness after PFA treatment and short-term curing under ambient conditions indicated its efficiency as an effective stabilizer. The dramatic improvement was mainly due to the hydration reactions of calcium-rich PFA, leading to stable cementitious compounds. Microstructural evolution of PFA treated and cured soil revealed the formation and deposition of new products in the inter and intra-aggregate pores, thereby forming strong inter-particle bonds and a dense matrix with refined pore structure. Further, the leaching tests confirmed that the cementation process minimized the bio-availability of toxic metals present in the treated soil by encapsulating in the newly formed water-stable compounds. These results demonstrated that recycled PFA could be successfully implemented as an environmentally and economically sustainable binder in road construction and rehabilitation applications, reducing stockpiles of this waste and associated ecological footprints.
4. Lightweight concretes based on wheat husk and hemp hurd as bio-aggregates and modified magnesium oxysulfate binder: Microstructure and technological performances
Construction and Building Materials, Volume 284, 17 May 2021, 122751
Using lightweight building materials from ecological resources reduces the environmental impact of buildings. Most attention has been paid to lime-based agro-concretes, but low binder-aggregate compatibility as well as slow strength gain are drawbacks. The use of magnesia-based binders has the potential to mitigate these problems. Here, a modified magnesium oxysulfate (MOS) cement was used to manufacture lightweight concretes using wheat husk, a highly available and unexploited resource, and hemp hurd as bio-aggregate. A combined microstructural-technological study was performed, filling gaps in existing literature. Through microstructural observations made by X-ray Powder Diffraction, microscopy imaging (optical, electron) and mercury porosimetry, mechanical and thermal properties in the different concretes were elucidated. It will be shown that the developed lightweight concretes are technologically competitive with lime-based ones, having the advantage of possessing high early strength.
5. A sustainability-oriented framework for the application of industrial byproducts to the base layers of low-volume roads
Journal of Cleaner Production, Volume 295, 1 May 2021, 126440
Roadway engineering works typically rely on the utilization of natural aggregates as building materials. However, growing pressures for sustainable roads are highlighting the importance of replacing virgin materials with industrial byproducts. Constructors worldwide are trying to select optimum soil-byproduct mixtures that have a fair trade-off between engineering properties, environmental impacts and material costs. This requires a multi-objective analysis to explore feasible mixtures that honor a set of preferences to mathematically identify the best compromised soil-byproduct mixture. In this paper, a sustainability-oriented framework is proposed for selecting optimum soil-byproduct proportions for unbound base layers of unpaved roads. A compromise programming tool is implemented to select a mixture that is statistically preferred over mixtures with different byproduct contents. The method is illustrated using technical, economic and environmental indicators that are easily measurable. Investigations are performed for different decision-making perspectives including the constructor’s, contractor’s and the environment’s viewpoints. Two byproducts from the steel industry are mixed in different proportions from 50% to 80% by weight with a clayey soil. The optimum mixture was obtained at a proportion of 70% byproduct and 30% clay. Monte Carlo simulations and sensitivity analysis of transport scenarios further supported this conclusion. Results demonstrate that mixture selection based only on strength properties provides inadequate optimum from a sustainable standpoint. The proposed framework can help road constructors incorporate environmentally-friendly materials in a cost-effective way, while maintaining the technical quality of base layers.
6. Biomarkers of phthalates and alternative plasticizers in the Flemish Environment and Health Study (FLEHS IV): Time trends and exposure assessment
Environmental Pollution, Volume 276, 1 May 2021, 116724
Restrictions on the use of legacy phthalate esters (PEs) as plasticizer chemicals in several consumer products has led to the increased use of alternative plasticizers (APs), such as di-(iso-nonyl)-cyclohexane-1,2-dicarboxylate (DINCH) and di-(2-ethylhexyl) terephthalate (DEHTP). In the fourth cycle of the Flemish Environment and Health Study (FLEHS IV, 2016–2020), we monitored exposure to seven PEs (diethyl phthalate (DEP), di-(2-ethylhexyl) phthalate (DEHP), di-isobutyl phthalate (DiBP), di-n-butyl phthalate (DnBP), butylbenzyl phthalate (BBzP, di-isononyl phthalate (DINP), and di-isodecyl phthalate (DIDP))and three APs (DINCH, DEHTP, and di-(2-ethylhexyl) adipate (DEHA)) by measuring multiple biomarkers in urine of 416 adolescents from Flanders, Belgium (14–15 years old). The reference values show that exposure to PEs is still widespread, although levels of several PE metabolites (e.g., sum of DEHP metabolites, mono-normal-butyl phthalate (MnBP) and mono-benzyl phthalate (MBzP)) have decreased significantly compared to previous human biomonitoring cycles (2003–2018). On the other hand, metabolites of DINCH and DEHTP were detected in practically every participant. Concentrations of AP exposure biomarkers in urine were generally lower than PE metabolites, but calculations of estimated daily intakes (EDIs) showed that exposure to DINCH and DEHTP can be considerable. However, preliminary risk assessment showed that none of the EDI or urinary exposure levels of APs exceeded the available health-based guidance values, while a very low number of participants had levels of MiBP and MnBP exceeding the HBM value. Several significant determinants of exposure could be identified from multiple regression models: the presence of building materials containing PVC, ventilation habits, socio-economic status and season were all associated with PE and AP biomarker levels. Cumulatively, the results of FLEHS IV show that adolescents in Flanders, Belgium, are exposed to a wide range of plasticizer chemicals. Close monitoring over the last decade showed that the exposure levels of restricted PEs have decreased, while newer APs are now frequently detected in humans.
7. Promoting sustainable cleaner production paradigms in palm oil fuel ash as an eco-friendly cementitious material: A critical analysis
Journal of Cleaner Production, Volume 295, 1 May 2021, 126296
Long term goals need to be set to promote the country’s circular economy (CE) as well as the cleaner environment by recycling waste materials into useful products. In pursuit of controlling environmental threats of carbon-based industrial wastes, different preprocessing techniques for their conversion into other value-added materials are being put in use. This review targets the purposeful utilization of massive amount of palm oil fuel ash (POFA), generated as a waste from power plants of palm oil processing mills in the major palm oil-producing countries. Currently, unrestrained disposal of POFA captures not only precious land but also creates environmental threats and health-related issues. Present work is an attempt to establish a sustainable cleaner production (SCP) system instead of unmanaged POFA disposal. Major palm oil producer countries should address the emerging issues of POFA related unsafe environment, energy consumption and landfill spaces by adopting reuse, reduce and recycle principles. Technically, this review also focuses on the use of POFA as a promising cementitious material in concrete production. It also maps the importance of POFA in concrete production as a cement replacement by presenting various state-of-the-art chemical reactions, mode of action of POFA for its pozzolanic reactivity in cement compositions and associated technical, environmental, and economic benefits. This will provide an alternative option and a sustainable solution for the global construction industry. It is conclusively evident from an extensive literature survey of 463 published results from last 26 years that POFA can be effectively used in concrete production to replace cement without compromising on its strength, performance, and durability. Based on the till that research work on POFA applications in the cement industry and other multiple areas, a circular economic model has been presented to support the concept of zero waste and SCP. It will stimulate the technical persons and decision-makers to make policies and strategies that can spotlight the effective use of POFA in multiple applications, primarily focusing on concrete production not only for curtailing the land and water pollution but also acquiring economic benefits.
8. Enhanced workability, durability, and thermal properties of cement-based composites with aerogel and paraffin coated recycled aggregates
Journal of Cleaner Production, Volume 297, 15 May 2021, 126518
The use of construction and demolition (C&D) wastes in building materials is a key step toward a sustainable construction industry. In this context, the application of recycled concrete aggregates (RCAs) in cement composite mixtures has been investigated by various researchers. The results available in the literature indicate that cement mortar adhered to the surface of RCAs leads to high water absorption and large porosity in cementitious mixtures. As a result, lower workability, durability, and mechanical properties in comparison to conventional aggregates are often known as the main attributes of mixtures containing RCAs. Additionally, improving the thermal energy storage capability of RCAs by using high-performance thermal insulation materials, such as phase change materials (PCMs) and aerogel can assist in minimizing the energy consumption in buildings. Accordingly, this paper aims at characterizing RCA mixtures with enhanced workability, durability, and thermal properties. The effect of using paraffin coated recycled concrete aggregates (PCRAs) and aerogel aggregates on the mechanical, thermal, and durability properties of cement composites are investigated in this paper. Results of dry density, compressive strength, water absorption content, permeable voids, thermal conductivity, rapid chloride migration test (RCMT), capillary water absorption, and scanning electron microscopy (SEM) tests along with energy-dispersive X-ray spectroscopy (EDX) are reported to evaluate the effect of several variables on the investigated concrete mixtures. Results of the conducted tests indicate that using PCRA significantly improves the durability characteristics of mixtures such as water absorption content, permeable voids, and RCMT, while it slightly decreases the compressive strength of mixtures with respect to the control mixture. In addition, aerogel aggregates significantly improve the thermal conductivity of mixtures while reduced the mechanical and durability characteristics.
9. Using cellulose nanocrystals to improve the mechanical properties of fly ash-based geopolymer construction materials
Engineering Science and Technology, an International Journal, Available online 7 May 2021
Ordinary Portland cement production is one of the biggest emitters of carbon dioxide. Consequently, there is a strong need for construction materials with lower environmental footprints. However, the development of alternative green construction materials requires a standardized framework. Although cellulose nanocrystals have shown considerable reinforcement potential in conventional construction materials, its effect on the mechanical properties of fly ash-based geopolymers as green construction materials is not known. Consequently, a detailed database outlining the cellulose nanocrystals interactions on the compressive strength, density, and corrosion resistance properties of geopolymers can optimize and guide further research efforts. The aims of this study were to firstly determine the effect of cellulose nanocrystals on the mechanical properties of fly ash-based geopolymers. Secondly, to produce a database of the effects of cellulose nanocrystals concentration and activator concentration on the mechanical properties of the formed geopolymers. Finally, to formulate an empirical framework to develop green construction materials. An empirical framework was developed alongside the cellulose nanocrystals-reinforced geopolymers, which were optimized using a statistical experimental design. The experimental results yielded the geopolymer property database. It was found that low cellulose nanocrystals concentrations (less than 0.5%) favoured the geopolymer mechanical properties. Using industrial wastes to produce green construction materials can divert industrial wastes from landfills and minimize the widespread use of environmentally degrading conventional construction materials. The framework developed in this study can facilitate the commercialization of green construction materials in industry.
10. Tensile behavior of flax textile reinforced lime-mortar: Influence of reinforcement amount and textile impregnation
Cement and Concrete Composites, Volume 119, May 2021, 103984
Companies and practitioners working in the civil construction sector are more and more aware and motivated to develop and adopt sustainable building materials, possibly obtained from renewable and locally available resources. As part of this common effort, special attention is being paid to an emerging class of materials generally referred to as bio-based composite systems.
In this context, this paper investigates the mechanical properties of a Textile-Reinforced Mortar (TRM) system produced with Flax textile embedded within a hydraulic lime-based mortar. The research aims at revealing the influence of either the reinforcement amount and the applied pre-treatment of the textile on the resulting tensile response and the cracking patterns exhibited by these TRM systems. The analysis of the results presented herein allows to have a comprehensive overview of the feasibility of using flax textiles for strengthening and retrofitting of existing structures.
11. Novel C-A-S-H/PCE nanocomposites: Design, characterization and the effect on cement hydration
Chemical Engineering Journal, Volume 412, 15 May 2021, 128569
Concrete is the most widely used building material in the world. With the development of the modern civil engineering construction, the rapid development of early-age strength of concrete is becoming more and more crucial. Nowadays, the early-age strength of concrete is generally enhanced by thermal curing at high temperature. However, the drawbacks of thermal curing include the high energy consumption and the adverse effect on the long-term strength of concrete, which promotes the development of green and highly-efficient accelerator. During the past decade, it has been found that C-S-H (calcium-silicate-hydrates) nanoparticles could act as the seeds for cement hydration and thus effectively enhance the early-age strength of concrete, which has drawn many research interests due to their economic and environmental benefits. This study proposes novel C-A-S-H (calcium-alumina-silicate-hydrates) nanocomposites by incorporating moderate Al into C-S-H in the presence of PCE (polycarboxylate superplasticizer), and find the formed C-A-S-H/PCE nanocomposites could remarkably promote the dispersion retention ability and the effect on early-age strength development of concrete comparing to traditional C-S-H nanoparticles. Moreover, this study also provides a basis for the production of green and cheap nano-seeding materials based on Al-rich wastes.
12. Impact of “healthier” materials interventions on dust concentrations of per- and polyfluoroalkyl substances, polybrominated diphenyl ethers, and organophosphate esters
Environment International, Volume 150, May 2021, 106151
Per- and polyfluoroalkyl substances (PFAS), polybrominated diphenyl ethers (PBDEs), and organophosphate esters (OPEs) are found in building materials and associated with thyroid disease, infertility, and impaired development. This study’s objectives were to (1) compare levels of PFAS, PBDEs, and OPEs in dust from spaces with conventional versus “healthier” furniture and carpet, and (2) identify other product sources of flame retardants in situ. We measured 15 PFAS, 8 PBDEs, and 19 OPEs in dust from offices, common areas, and classrooms having undergone either no intervention (conventional rooms in older buildings meeting strict fire codes; n = 12), full “healthier” materials interventions (rooms with “healthier” materials in buildings constructed more recently or gut-renovated; n = 7), or partial interventions (other rooms with at least “healthier” foam furniture but more potential building contamination; n = 28). We also scanned all materials for bromine and phosphorus as surrogates of PBDEs and OPEs respectively, using x-ray fluorescence. In multilevel regression models, rooms with full “healthier” materials interventions had 78% lower dust levels of PFAS than rooms with no intervention (p < 0.01). Rooms with full “healthier” interventions also had 65% lower OPE levels in dust than rooms with no intervention (p < 0.01) and 45% lower PBDEs than rooms with only partial interventions (p < 0.10), adjusted for covariates related to insulation, electronics, and furniture. Bromine loadings from electronics in rooms were associated with PBDE concentrations in dust (p < 0.05), and the presence of exposed insulation was associated with OPE dust concentrations (p < 0.001). Full “healthier” materials renovations successfully reduced chemical classes in dust. Future interventions should address electronics, insulation, and building cross-contamination.
13. Characterization and hydrophobic surface study of silicon-based TiO2, ZnO and recycled carbon additives on cementitious materials surface
Journal of Building Engineering, Available online 18 May 2021, 102689
The hydrophobic properties of cementitious mortar surfaces coated with silicone-based TiO2, ZnO and recycled nano carbon black (RNCB) filled composites prepared in different proportions to protect building materials were compared. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffractometer (XRD), 3D surface profilometry, surface roughness and contact angle tests were performed to evaluate the surface performance of hydrophobic samples. The results showed that the particles were uniformly distributed over the mortar surface of the hydrophobic samples. It was determined that the amount of TiO2 and ZnO particles in the crystalline phase is an important factor in crystallite sizes and lattice strain. For the ZnO-S2 sample, the contact angle of the water droplet showed hydrophobic behavior up to 155o. However, the contact angle of the 145° RNCB-S2 sample is important for low cost hydrophobic surface work. While the highest homogeneous roughness distribution (4.33 μm) was determined on the sample surfaces in the ZnO-S sample, the closest value to the ZnO-S sample was determined in the RNCB-S sample (3.47 μm). In this study, it was tried to prevent liquid ingress from the porous structure of mortar by forming a hydrophobic coating on the mortar surface. Especially, the hydrophobic properties of RNCB particles on the cementitious material surface are thought to be important in reducing the wettability on cementitious material surfaces.
14. Legacy and novel flame retardants from indoor dust in Antarctica: Sources and human exposure
Environmental Research, Volume 196, May 2021, 110344
The air humidity in Antarctica is very low and this peculiar weather parameter make the use of flame retardants in research facilities highly needed for safety reasons, as fires are a major risk. Legacy and novel flame retardants (nFRs) including polybrominated diphenyl ethers (PBDEs), hexabromocyclododecanes (HBCDs), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), Dechlorane Plus (DP), and other nFRs were measured in indoor dust samples collected at research Stations in Antarctica: Gabriel de Castilla, Spain (GCS), Julio Escudero, Chile (JES), and onboard the RRS James Clark Ross, United Kingdom (RRS JCR). The GC-HRMS and LC-MS-MS analyses of dust samples revealed ∑7PBDEs of 41.5 ± 43.8 ng/g in rooms at GCS, 18.7 ± 11.6 ng/g at JES, and 27.2 ± 37.9 ng/g onboard the RRS JCR. PBDE pattern was different between the sites and most abundant congeners were BDE-183 (40%) at GCS, BDE-99 (50%) at JES, and BDE-153 (37%) onboard the RRS JCR. The ∑(4)HBCDs were 257 ± 407 ng/g, 14.9 ± 14.5 ng/g, and 761 ± 1043 ng/g in indoor dust collected in rooms at GCS, JES, and RRS JCR, respectively. The ∑9nFRs were 224 ± 178 ng/g at GCS, 14.1 ± 13.8 ng/g at JES, and 194 ± 392 ng/g on the RRS JCR. Syn- and anti-DP were detected in most of the samples and both isomers showed the highest concentrations at GCS: 163 ± 93.6 and 48.5 ± 61.1 ng/g, respectively. The laboratory and living room showed the highest concentration of HBCDs, DPs, BTBPE. The wide variations in FR levels in dust from the three research facilities and between differently used rooms reflect the different origin of furnishing, building materials and equipment. The potential health risk associated to a daily exposure via dust ingestion was assessed for selected FRs: BDEs 47, 99, and 153, α-, β-, and γ-HBCD, BTBPE, syn- and anti-DP. Although the estimated exposures are below the available reference doses, caution is needed given the expected increasing use of novel chemicals without a comprehensive toxicological profile.
15. Effect of SiC powder on the properties of SiC slurry for stereolithography
Ceramics International, Volume 47, Issue 9, 1 May 2021, Pages 12442-12449
Silicon carbide (SiC) is a kind of structural ceramics with excellent properties and it is widely used in industrial fields. Stereolithography (SL) is a potential additive manufacturing technique to fabricate fine complex SiC components, the resin-based SiC slurry with superior rheological and photo-polymerization properties is important for SL. In this paper, we investigated the influence of SiC powder on the properties of the SiC slurries for SL. The physical characteristics of SiC powder such as particle size, size distribution and appearance were tested and observed, and their influence on the dispersion, sedimentation and photo-polymerization property of the SiC slurry were investigated and discussed in detail based on their correlative theory, we finally prepared SiC slurry with superior rheological and photo-polymerization properties, and fabricated the fine complex SiC green body with low defects, high accuracy and high bending strength successfully. The SiC slurry with the solid content of 40 vol% was fabricated by the SiC powder with the median diameter D50 ≈ 10.0 μm and a narrow particle size distribution, it is Bingham fluid with good fluidity and the viscosity of it is 464.40 mPa s under the shear rate of 51.08 s−1, the cured SiC parts with Z – axis dimension change of 0.75% was finally fabricated, the three points bending strength of it is 50.18 MPa. Our research work provides some fundamental understanding of the SL technique for fabricating fine complex SiC components, explored a suitable way to fabricate high quality SiC green parts through SL, and offers some valuable references for preparing SiC slurry with superior rheological and photo-polymerization properties.
16. Photocatalytic ethanol to H2 and 1,1-diethoxyethane by Co(II) diphenylphosphinate/TiO2 composite
Polyhedron, Volume 200, 15 May 2021, 115140
Through a facile solvothermal method, the novel composites of cobalt(II) diphenylphosphinate/TiO2 have been synthesized and used for photocatalytic hydrogen production in ethanol solution. The chemical composition and surface morphology were analyzed by XPS, XRD, ICP-OES, EA, IR and SEM. The composite CoTi10 showed high photocatalytic activity in H2 evolution that the quantity is ca. 1155.86 μmol/g for 3 h in ethanol solution under the illumination of UV–visible light source, which is 12 times higher than the commercial P25. The composites also exhibited unique selectivity for converting ethanol to 1,1-diethoxyethane in the photocatalytic process. Moreover, their good stabilities were revealed in the recycling test. It is thus clear that the composite can effectively inhibit the recombination of electron-hole pairs in photocatalytic reactions and lead to the enhanced hydrogen production rate.
17. An LCA-based model for assessing prevention versus non-prevention of construction waste in buildings
Waste Management, Volume 126, 1 May 2021, Pages 608-622
Waste generated by the Construction Sector represents an environmental problem in many countries. To achieve increasingly eco-efficient waste management, Life Cycle Assessment (LCA) provides an objective method for the quantification of the potential impact that waste management exerts on the environment. Traditionally, LCA has focused on the evaluation of non-prevention scenarios once the waste is generated, mainly by showing the benefits of recycling vs. disposal. Consequently, the literature has hardly addressed the positive environmental impacts caused by waste prevention, that is, the reduction at source, which constitutes the preferred option of any waste management hierarchy. Therefore, this study proposes a model to simulate the environmental performance of the prevention vs. the non-prevention of construction waste production. The model is applied to an urban system of residential buildings in Spain. The results provide evidence of the environmental benefits achieved with the prevention scenario. The prevention scenario reduces the construction waste generated in the non-prevention scenarios by up to 57%. Furthermore, it allows a potential reduction of up to 4.6 and 171.1 times the impact caused by the disposal scenario; and up to 1.7 and 8.3 times those of the recycling scenario. The model can be implemented in other contexts with other reference buildings, and enables the environmental benefits of reduction strategies to be studied, thereby providing a tool to guide and support decision-making during the building design stage. Moreover, the results obtained can help professionals and policymakers to incorporate effective construction waste prevention measures in waste prevention plans and programs.
18. Spatial autocorrelation, influencing factors and temporal distribution of the construction and demolition waste disposal industry
Waste Management, Volume 127, 15 May 2021, Pages 158-167
The construction and demolition waste disposal industry plays a vital role in improving the utilisation rate of construction and demolition waste worldwide, however, too little work has been devoted to the industrial economic analysis. To explore the economic pattern and promote the development of the construction and demolition waste disposal industry, the spatial autocorrelation and influencing factors were analysed, and a temporal development process was evaluated. Spatial measurement results show that the spatial autocorrelation of the construction and demolition waste disposal industry is significant at a 1% level. Per capita GDP, annual yield of construction and demolition waste, research and development level, transportation development level, human capital and education level positively affect the construction and demolition waste disposal industry. Conversely marketisation level negatively influences the development of the construction and demolition waste disposal industry. Temporal analysis results reveal that development of the construction and demolition waste disposal industry accelerated significantly in 2016 and increasing by 35.79% because of a policy stimulus. Suggestions on regional management plans and targeted policies for special cities were proposed. A novel perspective for investigating the C&D waste disposal industry was developed, which may be very helpful for researchers from other countries to study the agglomeration effect in various waste disposal industries. The findings can contribute to the development plan of the C&D waste disposal industry, and be of value to investors to make investment and site planning.
19. Framework for characterizing the time-dependent volumetric properties of aerated cementitious material
Construction and Building Materials, Volume 284, 17 May 2021, 122781
The expansion in cementitious materials can be generally caused by a generation of air bubbles by adding pore generation materials. Even though these materials are beneficial for forming porous structure, they can cause drastic changes in fresh and hardened properties due to their reactions with cementitious materials. To identify these relationships, an accurate measurement of volumetric properties of expansive cementitious materials in the fresh state is needed to be developed. This study proposes a non-contact testing framework for quantitative analysis of time-dependent volumetric properties of expansive cementitious materials using ultrasonic sensor and depth camera during a mixing process. To validate the proposed framework, two types of pore-generation materials—aluminum powder and air-entraining (AE) agent—were used to prepare the aerated cementitious materials as expansive materials. In the estimations of their volume changes, a depth camera-based scheme provided accurate results by scanning entire rough surfaces of testing samples. To suggest the relationship of volume changes with fresh and hardened properties, various tests for analyzing rheological properties, compressive strength, density, and porous microstructure were also performed. All tested results of the aerated cementitious series showed strong correlations with their volume changes, which were measured by a depth camera system. This experimental study indicated the importance and potential of the proposed framework as a practical and reliable means for characterizing time-dependent fresh properties of cementitious materials.
20. Behavior of alkali-activated pozzocrete-fly ash paste modified with ceramic tile waste against elevated temperatures and seawater attacks
Construction and Building Materials, Volume 285, 24 May 2021, 122866
Huge quantities of ceramic tile waste are disposed annually in an unsafe manner, causing some environmental problems including air and soil contamination. So the re-use of such waste would be the perfect solution to get rid of these problems. This research focused on exploring durable and thermal stable geopolymer-based alkaline activation of pozzocrete-fly ash (PFA) doped with different ratios of ceramic tile waste (CW) compared to their plain mixtures under normal conditions. The PFA waste was modified upon partially replaced with the CW waste at replacement levels of 0%, 5%, 10%, 15% and 20%, by weight. All PFA-CW pastes activated with a mixture of NaOH and Na2SiO3 solutions. The hardened specimens were cured in 100% RH at 40 ± 2 °C for 1, 7, 14 and 28 days. After 28 days, some specimens were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C and 1000 °C with a heating rate of 5 °C/min. Another batch of specimens were subjected to seawater for 1, 3 and 6 months. The mechanical properties as well as microstructure analysis prior and after exposure were monitored. The geopolymer phases were examined by Fourier transform infrared spectroscopy (FT-IR), Thermogravimetric analysis plus its derivative (TGA/DTG) and Scanning electron microscopy (SEM). The findings indicated that the CW waste has a positive effect on the properties of PFA-geopolymer. The inclusion of 10% CW enhanced the properties in terms of compressive strength and microstructure before and after exposure to high-temperature and seawater solution.