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:

– Gắn đa dạng sinh học vào thiết kế đô thị

– Các dự án thành phố thông minh chống COVID-19: kinh nghiệm từ Trung Quốc

– Một cách tiếp cận mới để phát hiện và thiết kế cấu trúc sống của môi trường đô thị

– Đánh giá hiệu quả của không gian mở đô thị để đạt được các tiêu chuẩn của thành phố bền vững và có khả năng chống chịu: nghiên cứu thí điểm về hai công viên đô thị ở Dublin, Ireland

– Thiết kế cảnh quan kiến ​​trúc đường phố dựa trên Internet of Things và hệ thống GIS không dây

– Nghiên cứu môi trường nhiệt của vỉa hè trong các cấu trúc đường đô thị khác nhau

– Đặc điểm không gian xanh đô thị ảnh hưởng như thế nào đến sự đa dạng hoạt động thể chất trong môi trường xây dựng mật độ cao?

– Hệ thống năng lượng hiệu quả và điều tiết thông minh cho chiếu sáng đường phố

– Tối ưu hóa tiềm năng bóng mát của cây trồng bằng cách tính đến bối cảnh cảnh quan

– Hướng tới quản lý tài sản theo định hướng người dùng đối với hệ thống đường sắt đô thị

Khoa học và công nghệ trong lĩnh vực kiến trúc, xây dựng:

– Ảnh hưởng của sợi bột giấy xenlulo đến tính năng vật lý, cơ học và nhiệt của vật liệu ép đùn từ đất

– Ưu tiên các kích thước và hạng mục bền vững cho các công trình nhà ở trong khu vực khí hậu nhiệt đới

– Thông gió cho các tòa nhà có hệ thống thu hồi nhiệt

– Ảnh hưởng của bố trí không gian đến hiệu suất năng lượng của các tòa nhà văn phòng ở ba vùng khí hậu

– Khả năng cách âm của vách ngăn thạch cao: phân tích vách ngăn đơn và vách kép

– Hệ thống quản lý tòa nhà thông minh: đặc điểm kỹ thuật hoạt động và yêu cầu thiết kế

– Triển khai tích hợp Thiết kế và Xây dựng Ảo (VDC) và hệ thống phân phối dự án tinh gọn (LPDS)

Vật liệu xây dựng:

– Khả năng chịu nhiệt độ cao của vật liệu kết dính thay đổi pha ở nhiệt độ cao

– Hiệu suất của vật liệu tổng hợp gốc xi măng cốt sợi ở nhiệt độ cao

– Nghiên cứu so sánh các tính chất cơ học, độ co ngót tự sinh và tính dễ nứt của bê tông hoạt tính kiềm và bê tông xi măng poóc lăng thường

– Xốp cách nhiệt siêu nhẹ không cháy dựa trên vi cầu thủy tinh rỗng với cấu trúc liên kết điểm

– Đánh giá quan trọng về việc sử dụng xỉ đồng (CS) làm thành phần thay thế trong bê tông

– Sử dụng bền vững chất thải sinh khối-tro trấu làm vật liệu rắn chắc mới trong công trình địa kỹ thuật

Xin trân trọng giới thiệu!

QUY HOẠCH ĐÔ THỊ

1. Building biodiversity into the urban fabric: A case study in applying Biodiversity Sensitive Urban Design (BSUD)

Urban Forestry & Urban Greening, Volume 62, July 2021, 127176

Abstract

Biodiversity within cities is fundamental for human health and well-being, and delivers a wide range of critical ecosystem services. However, biodiversity is often viewed as an afterthought or final addition once an urban development nears completion. As such, provisions for biodiversity are typically tokenistic and do not achieve the experience of everyday nature that people need. Considering biodiversity requirements at the start of an urban development allows for strategic, intentional design with biodiversity enhancement in mind. Biodiversity Sensitive Urban Design (BSUD) is a protocol that aims to create urban areas that deliver on-site benefit to native species and ecosystems through the provision of essential habitat and food resources. Here we present a case study demonstrating how BSUD methods can be used to (a) encourage successful outcomes for nature, (b) improve the aesthetics and liveability of the urban form, and (c) engage stakeholders in a process that supports other aspects of urban design including park and streetscape design. Fishermans Bend (Melbourne) is the largest urban renewal project in Australia, and one of the first of this scale to explicitly include biodiversity targets. We outline the methods used to co-create biodiversity objectives with diverse stakeholders, and how these, combined with a quantitative analysis of their potential biodiversity impact, were translated into clear design and planning recommendations. We critically reflect on the success of this method for 1) communicating and facilitating provisions for biodiversity across different stakeholders and 2) providing clear messaging around biodiversity across different planning disciplines.

2. Smart city projects against COVID-19: Quantitative evidence from China

Sustainable Cities and Society, Volume 70, July 2021, 102897

Abstract

The outbreak of COVID-19 pandemic worldwide has brought huge challenges to urban governance. Whether the smart city projects play a significant role in the COVID-19 prevention and control process is a question worthy of attention. Based on the data of COVID-19 confirmed cases and the smart cities projects investment in China cities, our empirical results show that smart city projects have significantly reduced the number of COVID-19 confirmed cases. Specifically, for every 1 million yuan increase in smart city investment per 10,000 people, the number of COVID-19 confirmed cases per 10,000 people would decrease by 0.342. The heterogeneity analysis results show that the effect of the smart city projects on COVID-19 in the spread phase inside a city is stronger than that in the input phase. In addition, the effect differs for cities with different population sizes. This study provides quantitative evidence of the impact of smart city projects on COVID-19 prevention and control.

3. A new approach to detecting and designing living structure of urban environments

Computers, Environment and Urban Systems, Volume 88, July 2021, 101646

Abstract

Sustainable urban design or planning is not a LEGO-like assembly of prefabricated elements, but an embryo-like growth with persistent differentiation and adaptation towards a coherent whole. The coherent whole has a striking character – called living structure – that consists of far more small substructures than large ones. To detect the living structure, natural streets or axial lines have been previously adopted to be topologically represent an urban environment as a coherent whole. This paper develops a new approach to detecting the underlying living structure of urban environments. The approach takes an urban environment as a whole and recursively decomposes it into meaningful subwholes at different levels of hierarchy (or scale) ranging from the largest to the smallest. We compared the new approach to natural street and axial line approaches and demonstrated, through four case studies, that the new approach is better and more powerful. Based on the study, we further discuss how the new approach can be used not only for understanding but also – probably more importanly – for effectively designing or planning an urban environment to be living or more living.

4. Assessing the performance of urban open space for achieving sustainable and resilient cities: A pilot study of two urban parks in Dublin, Ireland

Urban Forestry & Urban Greening, Volume 62, July 2021, 127180

Abstract

The urban environment is at increased risk of unforeseen disturbances associated with climate change and urbanisation. Urban open space, when appropriately located, designed and managed, can potentially support underlying ecosystem services and provide multiple social-ecological benefits. Conversely, poor planning or design can result in mono-functional open space with potentially negative results for the built environment. To anticipate future uncertainty and create more sustainable and resilient cities, it is important to assess the performance of urban open space. This paper provides a deeper understanding of resilience at the scale of open space within the urban fabric and suggests a framework conceptualising resilience with an emphasis on ecosystem services and spatial configuration. A hierarchical index system (HIS) comprising twenty-six measurable indicators and an associated assessment methodology is proposed to evaluate the performance of urban parks in terms of their contribution to urban resilience and sustainability. The applicability of the HIS and assessment methodology is examined in a pilot study by assessing two urban parks in Dublin, Ireland. This paper contributes to the coupling of resilience thinking with urban design by proposing an evaluation method that assists design professionals and urban decision-makers in evaluating the performance of existing schemes and new proposals for urban open space. This paper will help a range of stakeholders better understand the settings of these spaces through scientific evidence.

5. Street architecture landscape design based on Wireless Internet of Things and GIS system

Microprocessors and Microsystems, Volume 80, February 2021, 103362

Abstract

An infrastructure that provides geospatial analysis, better understands simulations, great potential for visualizing natural and artificial landscapes, and the universal recognition of the use of the Wireless Internet of Things. Everyday devices, whose platform is the Internet of Things, will be smarter in their daily processing, richer in their daily communication, and smarter. The Wireless Internet of Things still wants its landscape design. Still, its impact is already looking at the scene where the Wireless Internet of Things and GIS (Geographic Information System) systems were connected to make incredible advances. It opens up architecture-specific research and the usual architectural landscape area. It can be used for soil mapping studies and can be used for remote sensing in other engineering areas to obtain a wide range of weather compensation. It encourages the use of geographic information systems for geotechnical applications in soil. Geographic information systems can manipulate georeferenced information to be displayed, store, assemble and create georeferenced data from existing data, and generate multiple missing spatial data based on the attributes attached to it. The system briefly introduces street architecture landscape applications and promotes a street landscape design environment for Wireless Internet of Things and GIS system architecture. The proposed system is described as a thing and GIS as network technology, especially in smart design, street architecture and landscape wireless network connectivity. This is an overview of smart network providers, first to help explore some essential landscapes, equipped with wireless internet and geographic information systems, and how it is used in street architecture.

6. Study of the thermal environment of sidewalks within varied urban road structures

Urban Forestry & Urban Greening, Volume 62, July 2021, 127137

Abstract

Vehicle-oriented transportation has been dominating road design for decades and worsening the urban outdoor thermal environment. Introducing the concept of human-oriented design in road reconstruction, this study considered road orientation, number of planting strips, and leaf area index (LAI) of trees when developing alternative road structures that aims to provide pedestrians a more satisfying walking experience. The ENVI-met V4 model, was used to simulate the thermal environment of sidewalks within the scenarios. Results demonstrated that road orientation had significant but time-varied effects on mean radiant temperature (T_mrt) and physiological equivalent temperature (PET). Two T_mrt and PET peaks were noticed in East-West (EW) oriented roads; but only one peak was found in North-South (NS) roads due to that the aisle buildings on NS roads shaded sidewalks and reduced the solar radiation received in the morning.

Changing tree’s LAI from low to high on EW and NS roads can reduce the mean T_mrt by 5.5 and 3.0 °C, and the mean PET by 3.2 and 1.7 °C, respectively. Simulation results also showed that adding one more planting strip in the middle of roads did not reduce the mean T_mrt (all cases less than 1.7 °C) and mean PET (all cases less than 1.2 °C) much. A significant synergistic cooling effect from road orientation, number of planting strips, and LAI of trees on the sidewalks’ T_mrt and PET was observed. Thus, the number of planting strips and LAI of trees could be more precisely applied while considering road orientation. These results provide quantitative and alternative information for designers to create a better walking experience for pedestrians.

7. How does urban green space feature influence physical activity diversity in high-density built environment? An on-site observational study

Urban Forestry & Urban Greening, Volume 62, July 2021, 127129

Abstract

Urban green space (UGS) plays an important role in maintaining and promoting public health because it provides opportunities for outdoor physical activities (PA). Many studies have proved that different UGS characteristics, such as area, shape, distance, etc., have a certain impact on the intensity or frequency of PA. It is noteworthy that most studies are completed on a city scale, which explains how ensemble characteristics of a park affect PA. However, few researchers have explored the relations between UGS features and physical activities at the parcel level. To address this gap, this study has investigated the effect of multiple features of UGS on the diversity of PA, with downtown Shanghai as the study site.

To identify types of PA and features of UGS based on on-site observation of a total of 101 sites in five urban parks located in a central district of Shanghai, China, we established an ordinal logistic regression with total types of PA (PA diversity hereafter) as the dependent variable and UGS characteristics as independent variables. The results show that green coverage ratio and diversity of shrubs are positively related to PA diversity, while diversity of trees has an inverse impact. Moreover, the paved area shape index and green view ratio are negatively correlated with PA diversity, which suggests that the irregular shape of paved areas with winding edges and excessive green view ratio are factors detrimental to PA diversity. These findings provide pertinent guidance in the design of UGS for the promotion of PA.

8. Smart regulation and efficiency energy system for street lighting with LoRa LPWAN

Sustainable Cities and Society, Volume 70, July 2021, 102912

Abstract

Public lighting installations represent an important consumption in smart cities. Therefore, it is necessary to implement energy saving solutions. In this sense, the use of smart meters (SM) provides a fundamental tool in the development of energy saving systems, which require monitoring and control in real time. The information flow generated requires an efficient communication system. Long Range (LoRa) protocol sends information across long distances with very low energy consumption. For this reason, it is especially interesting to implement in street light (SL) installations. This research designs a control, monitoring and energy saving system for SLs composed of three devices: Gateway for Street Lights System (GWSLS), Operating and Monitoring Device for Street Lights (OMDSL), and Illumination Level Device (ILD). Street Lights Regulation (SLR) algorithm was developed to dynamically control the lighting level. Lighting levels are selected using the Artificial Bee Colony (ABC) optimization algorithm, which is fast, reliable and accurate. Measured data is sent to the GWSLS gateway by the OMDSLs installed with the LoRa network and uploaded to the cloud using Firebase.

9. Assessment of city sustainability from the perspective of multi-source data-driven

Sustainable Cities and Society, Volume 70, July 2021, 102918

Abstract

From the perspective of multi-source data-driven, this paper combined the traditional assessment data with the network data, that is, integrating the behavioral guidance ideas and the emotional needs of the public in the assessment process. Through the emotional analysis of the network data, the subjective weight of the social, economic, and environmental systems were determined. This method not only reduces the cost of group decision making but also improves the assessment effect. At the same time, the objective weight with behavioral guidance was obtained by dynamic data analysis of the traditional assessment data. The sustainability performances of 14 cities in Liaoning, China were investigated. The results indicate that the sustainability was not ideal, most cities showed a downward trend. In addition, this paper concluded that the public in Liaoning paid the highest attention to the environmental system, followed by economic system and social system. Through curve fitting regression of the results, it is seen that in at this stage, it is not that the greater the indicator improvement of one system, the better the development of the other systems. It is suggested to make overall plans for the development of the three systems in light of the actual situation.

10. Toward user-oriented asset management for urban railway systems

Sustainable Cities and Society, Volume 70, July 2021, 102903

Abstract

Managing public infrastructure is becoming more complex due to aging assets, increasing demand, and budget limitations. Besides these challenges, best practices recommend putting stakeholders (specifically end-users) in the center of asset management planning for public assets incorporating provided services in the decision-making process to achieve sustainable cities goals. This study improves the classical asset-based approach and proposed a user-oriented platform to maintain urban railway systems. The model is applied to the Toronto regional railway network (Go Transit) in Canada and the Greater Montreal regional railway network (Exo). Results indicate that a proactive approach significantly can save money and bring higher value and performance for the agency. The user-oriented platform was able to push budget allocation toward enhancing provided and potential services for users. The same idea can be extended to other transit systems as well as other infrastructure.

11. Outdoor thermal performance of green roofs across multiple time scales: A case study in subtropical China

Sustainable Cities and Society, Volume 70, July 2021, 102909

Abstract

In recent years, roof greening technologies have been developed and implemented worldwide, as green roofs are an effective nature-based solution for alleviating outdoor heat and reducing building energy costs. While most observational green roof studies have investigated the cooling effect of model or test plots, few studies have conducted full-scale measurements; however, to guide green roof implementation, the thermal performance of full-scale roofs is crucial. This experimental study explored the ability of extensive green roofs to reduce outdoor temperatures on multiple time scales. The outdoor cooling effect of green roofs and the main factors that drive its performance were analyzed using long-term observational data collected from May 2016 to April 2019 in Nanjing, China. The results suggest that the cooling effect of green roofs exhibits significant diurnal, seasonal, annual, and vertical trends, and that the cooling performance across different time scales corresponds to weather and soil characteristics. The best cooling effect occurred at a height of 60 cm. The green roof displayed a temporary diurnal warming effect but had a good cooling effect on a seasonal time scale, with the largest amount of cooling occurring during the summer (average of 0.28 °C). The findings of this study can support the development, management, and maintenance of green roofs in subtropical areas.

12. Optimizing the shade potential of trees by accounting for landscape context

Sustainable Cities and Society, Volume 70, July 2021, 102905

Abstract

Urban trees provide important cooling effects and lower the human health risks associated with UV radiation through shading. However, maximizing the shade potential of trees to improve the benefits to the health and sustainability of cities is not well studied. To explore whether optimizing the spatial pattern of buildings and trees could improve the shading capacity of trees, we sampled 65 neighborhoods in Beijing, China, and used ground-based light detecting and ranging (LiDAR) data and the solar radiation tool in ArcGIS™ to describe the shade pattern. We chose eight landscape metrics to quantify the landscape pattern of buildings and trees. We found that 56.4 % of potential tree shade in Beijing’s neighborhoods was lost to building shade, and we proposed a new concept of shade efficiency of trees (SET) to quantify this inhibition effect of buildings on trees. In addition, trees also weaken each other’s shade potential, as the shade provided by a unit area of trees declines sharply with increasing tree cover. Optimizing the spatial pattern of buildings and trees could ease those inhibition or weakening effects, and enhance the shading capacity of trees.

13. Influence of permeability ratio on wind-driven ventilation and cooling load of mid-rise buildings

Sustainable Cities and Society, Volume 70, July 2021, 102894

Abstract

Natural ventilation potential in terraced buildings is affected by numerous parameters such as permeability ratio, distribution pattern, depth of terraces, etc. This research aims to evaluate the impact of permeability ratio on natural ventilation potential and cooling load of a terraced office building in the hot- humid climate. To this end, one solid block and eight porous models with different permeability ratios (20 %–30 %–40 %–50 %) and random distribution patterns were simulated and analyzed by Energyplus engine and computational fluid dynamics (CFD). For better comparison, two distribution patterns for each permeability ratio were simulated. CFD simulations were validated according to the wind-tunnel measurements. The cooling load amount, mean and maximum airspeed as well as the mean age of air in terraces and offices were used to evaluate the best configurations of porous buildings.

The results show that increasing the permeability up to 50 % will enhance the interior and inlet airspeed by 38.59 % and 49.07 % compared to the solid case. Simulations proved that a small change in porosities from 20 % to 30 % resulted in a significant difference in mean and maximum airspeed in terraces. The case with 50 % permeability ratio indicated higher values of mean and maximum airspeed in terraces. The mean age of air amount follows a descending process from the permeability ratio of 0–30 % and then increases gradually. The 30 % porous model with 30.8 s mean age of air is considered as the best case.

According to the results, the introduction of permeability does not leave a positive effect on cooling energy demand despite natural ventilation performance. Although porosity reduces the solar radiation heat gain and increases the natural ventilation potential, porous models indicated high values of cooling energy consumption. This is due to the high amount of exposed surface area in porous models which leads to an increase of cooling energy demand up to 2.7 % compared to the solid case.

As a result, among the permeable models, the best natural ventilation performance and the lowest cooling energy consumption are attributed to 50 % and 20 % permeable groups respectively.

This study helps the designers to better understand the ventilation and energy performance of a porous model and to improve the energy-efficient buildings in hot-humid regions.

14. Effect of urban form on microclimate and energy loads: Case study of generic residential district prototypes in Nanjing, China

Sustainable Cities and Society, Volume 70, July 2021, 102930

Abstract

To conduct a more comprehensive evaluation regarding the correlations between urban form, microclimate and energy performance of buildings, this study investigates eight generic residential district prototypes in Nanjing, China. Cases are characterized based on form indices such as the floor area ratio (FAR), surface area ratio (SAR) and mean sky view factor (SVF). A co-simulation method combining ENVI-met and EnergyPlus is proposed to simulate the microclimate, represented by average conditions around the exterior surfaces of all buildings in the studied district, and building energy loads during typical summer and winter days. The results show that, generally, air temperature and direct shortwave radiation are negatively correlated with the SAR. The cooling and heating loads are negatively correlated with the FAR and SAR, and positively correlated with the mean SVF. The differences in energy loads can reach 23.4 % with obvious deviation of the regression analyses of hourly heating loads and air temperature if neglecting the microclimate effect.

15. Land availability in Europe for a radical shift toward bio-based construction

Sustainable Cities and Society, Volume 70, July 2021, 102929

Abstract

The renovation and construction of buildings presents an opportunity for climate change mitigation in urban environments. Bio-based construction is particularly promising since the plant’s sequestered carbon offsets the building’s carbon emissions. However, the required land to cultivate suitable biomass and the feasibility of environmentally sustainable materials for resilient cities should be understood. This study analyzes timber, straw, hemp and cork construction and renovation in Europe. A prediction-based model, tuned-up on four systems (built environment, natural environment, carbon balance, industrial processing), converts construction activities until 2050 into required material, embodied land and carbon storage. A novel material-land nexus concept analyzes the required land for bio-based construction. Land transformation is not analyzed. The aim is to evaluate the biomass supply considering the current cross-sectoral use of land in Europe. The results indicate that current forests and wheat plantations are more than sufficient for supplying construction materials. Straw seems better than timber, in terms of resource availability and carbon storage potential. Cork is only favorable locally in southern dry countries. The current legal limitations hinder hemp’s potential at a large scale. A wider application of bio-based materials remains unrealistic until an appropriate legal framework is provided.

16. Understanding policy and technology responses in mitigating urban heat islands: A literature review and directions for future research

Sustainable Cities and Society, Volume 70, July 2021, 102873

Abstract

Policy and technology responses to increased temperatures in urban heat islands (UHIs) are discussed in a variety of research; however, their interaction is overlooked and understudied. This is an important oversight because policy and technology are often developed in isolation of each other and not in conjunction. Therefore, they have limited synergistic effects when aimed at solving global issues. To examine this aspect, we conducted a systematic literature review and synthesised 97 articles to create a conceptual structuring of the topic. We identified the following categories: (a) evidence base for policymaking including timescale analysis, effective policymaking instruments as well as decision support and scenario planning; (b) policy responses including landscape and urban form, green and blue area ratio, albedo enhancement policies, transport modal split as well as public health and participation; (c) passive technologies including green building envelopes and development of cool surfaces; and (d) active technologies including sustainable transport as well as energy consumption, heating, ventilation and air conditioning, and waste heat. Based on the findings, we present a framework to guide future research in analysing UHI policy and technology responses more effectively in conjunction with each other.

17. Finding optimal reconstruction plans for separating trucks and passenger vehicles systems at urban intersections considering environmental impacts

Sustainable Cities and Society, Volume 70, July 2021, 102888

Abstract

Separating trucks and passenger vehicles (STPV) systems in urban road networks is an effective way to reduce damage to the environment and public health. The STPV systems for urban networks have different circumstances and objectives than those for freeways. For example, environmental impacts and public health are emphasized more in urban areas than on freeways. In this paper, we propose an identification method for determining the optimal reconstruction plans for STPV systems at urban intersections, while considering the environmental impacts. Before proposing the identification method, we analyze the characteristics and applicability of reconstruction plans for STPV systems, and then propose an evaluation index system that includes fuel consumption and vehicle exhaust pollutant values for the STPV system. The proposed identification method incorporates a principal component analysis (PCA) into a simulation model. Using the proposed method, we can score alternative reconstruction plans, so as to determine the optimal reconstruction plans for specific urban intersections. We illustrate the proposed method through a case study of a real urban intersection. The proposed method provides a solid basis for academic research and industrial applications based on STPV systems for urban intersections.

18. Prediction of surface temperature of building surrounding envelopes using holistic microclimate ENVI-met model

Sustainable Cities and Society, Volume 70, July 2021, 102878

Abstract

Simulating the building’s surface condition as one of the important factors helps to predict the building’s energy consumption, mould growth and deterioration of materials.

A microclimate ENVI-met model is one type of the existing software that can predict the building’s surface temperature by considering the urban texture as well as the physical properties of the material.

Since accurate determination of climatic variables largely depends on the adjustment of different computational parameters, this paper aims to evaluate the reliability of the ENVI-met with different model settings for both summer and winter in Hanover, Germany.

According to the model verification, it is suggested to apply full-forcing weather data based on cloud cover for simulations and set a building’s inside temperature constant during the winter and vary during the summer. Also, comparing the different facade modes shows that for the exposed smooth facade, the predicted surface temperature based on DIN 6946 is more accurate than the MO method.

Finally, the accuracy of the model in predicting the building’s surface temperature varies, depending on the urban structure and climate condition. The model is more reliable in common urban areas than semi-closed spaces. Moreover, an average RMSE during summer is ∼ 2.2 °C higher than in winter.

19. A sustainable mobility strategy based on electric vehicles and photovoltaic panels for shopping centers

Sustainable Cities and Society, Volume 70, July 2021, 102891

Abstract

The transition from conventional centralized energy production to a distributed one may represent one of the solutions to reduce greenhouses emissions. The present work aims at proposing a novel approach for energy and environmental issues, related to the high density of vehicular traffic for shopping centers by introducing photovoltaic panels and electric vehicles into the energy system. In order to achieve such goal a specific case study was developed for the main shopping centers located in the Campania Region, South of Italy. Two well-known simulation platforms, EnergyPLAN and TRNSYS, were purposely integrated. TRNSYS is used to develop a dynamic model of a shopping and the outputs were used as EnergyPLAN inputs to evaluate the role that this sustainable layout can play within the different sectors. Environmental, energy and economic analyses are performed for three different scenarios including the baseline one at 2019, 2030 and 2050. The proposed system can cover about 45.7 % of the shopping centre electric demand. At a regional scale, in the 2050 scenario the yearly reduction of CO₂ and energy consumption are 42.0 kt and 160.0 GW h, respectively. The economic results show a SPB (Simple Pay Back) of 2 years and a PI (Profit Index) of 5.4.

20. An experience-based mining approach to supporting urban renewal mode decisions under a multi-stakeholder environment in China

Land Use Policy, Volume 106, July 2021, 105428

Abstract

As a complex systematic process, urban renewal needs to balance the multiple goals that transfer the original socio-economic foundation to the contemporary social-economic needs under a multi-stakeholder environment. The urban renewal mode decision determines the planning direction in an urban renewal project. How to select options from different urban renewal modes before implementation phase has been a decision-making dilemma. No existing method yet is available to give a satisfactory solution. Therefore, an existing experience-based method for analyzing and summarizing rules of urban renewal mode decision is suitable for this study. This paper adopts experience-based mining method to extract practical experiences from previous urban renewal projects for supporting urban renewal mode decisions with involvement of multi-stakeholder. Data are retrieved from materials of urban renewal projects in China, and an experience-based mining system of urban renewal mode decisions is constructed through text mining and case experience engine. The results reveal that: (1) Urban renewal mode decisions can be supported by experience extracted from case base of urban renewal mode decisions; (2) Urban renewal modes can be classified to development modes (conservation, renovation and redevelopment), resettlement modes (on-site resettlement and off-site resettlement), mode decisions relate to development foundation, development demand and multi-stakeholders’ decision-making role; (3) Different groups of stakeholders represent differentiated renewal demand preferences. The decision-making roles of some groups are not fully available in current urban renewal practices. The experience-based mining approach provides practical support for urban renewal mode decisions that could be relevant key points for guidance of future urban renewal decision-making in China.

KHOA HỌC VÀ CÔNG NGHỆ TRONG LĨNH VỰC KIẾN TRÚC, XÂY DỰNG

1. Computational studies on the airflow developed by the building-integrated passive solar energy system

Abstract

Ventilation and cooling demand are expected to rise in the next decades. Sustainable standalone solar passive air ventilation technique could be one of the clean options. In this study, a building-integrated passive solar energy technology (BIPSET) consists solar photovoltaic (PV) and solar still, was implemented for attaining multiple outputs, such as air ventilation, power and clean water in a building prototype proposed based on Chief Minister’s solar powered green house scheme, Government of India. Solar PV and solar still were connected separately with single chimney using necessary duct connections. The heat gain in the PV panels was used for air ventilation inside the building. Computational fluid dynamics analysis was carried out in SOLIDWORKS-2017 Flow simulation software to study the airflow behaviour, such as air change per hour, heat gain and efficiencies in the building-integrated system. The results are in good agreement with experimental values for both sunny and cloudy conditions. This solar still duct arrangement reduced the airflow inside the building in noon hours by 30%. However, it improved the airflow by 8% in the evening hours. The present system is in accordance with standards like ASHRAE 62.1–2010 and GRIHA, which indicates its commercial applicability. Moreover, the environment analysis indicates that the system offers CO₂ savings of 17.5 kg/year by adopting passive air ventilation. A modified integrated system was proposed to utilize the heat energy from the solar still for air ventilation by altering the duct arrangements.

2. Image-based occupancy positioning system using pose-estimation model for demand-oriented ventilation

Journal of Building Engineering, Volume 39, July 2021, 102220

Abstract

Dynamic changes in the position, number, and activities of occupants create various indoor scenarios that affect the operation of and energy required for heating, ventilation, and air conditioning (HVAC) systems. HVAC systems can use less energy by adapting their operational parameters according to the occupant distribution. However, accurate and non-intrusive occupancy positioning systems have yet to be established for conventional HVAC and more recently developed demand-oriented ventilation (DOV) systems. Herein, a novel image-based occupancy positioning system is proposed. This system uses multiple cameras to capture images from different views and a computer to perform digital image processing and three-dimensional (3D) reconstruction. Data fusion and 3D reconstruction algorithms were developed based on skeleton key points extracted from the images with a human pose estimation model. The entire system was built and tested in a multi-function room under two different scenarios. The results showed that the system provides positioning and orientation information for a dozen of people in real time. Because the system requires an ordinary computer and conventional surveillance cameras, it can be integrated into existing video surveillance systems to avoid privacy issues. As the speed of digital image processing and computer calculations increases, the cost of the system will decrease; these characteristics provide a solid foundation for the operation of highly efficient DOV systems.

3. Cyclic behavior of bracket connections for cross-laminated timber (CLT): Assessment and comparison of experimental and numerical models studies

Journal of Building Engineering, Volume 39, July 2021, 102197

Abstract

This paper reports the comprehensive test and numerical models assessments for uniaxial cyclic behaviors of standard bracket connections for cross-laminated timber (CLT). Five analysis methods are compared for the determination of yield points of CLT connections. The applicability of the methods to various types of CLT bracket connections is discussed in order to identify the most universal approach. Key mechanical properties of bracket connections such as strength, stiffness, yield point, failure point and ductility are shown and compared. Pinching4 hysteretic model is used and calibrated to match the experimental hysteretic curves. The damage index error based on energy-based accumulation principle is applied to assess the precision of the model on hysteretic details. It is found that the Yasumura&Kawai approach provids a suitable estimation of the yield point based on bilinear approach, avoiding underestimation like the CSIRO and Karacabeyli&Ceccotti methods and improving results from the methods of EN 12512 and ASTM E2126. The damage indicator can precisely indicate the quality of correlation between experimental results and model predictions. The Pinching4 model is proved the ability in modeling the cyclic experimental uniaxial behavior of the CLT bracket connections. It can capture most details of hysteretic load-displacement curves and offer closer predictions to the test results in the advanced stage of loading to damage. But it has limited abilities for modeling high unloading stiffness at the initial stage for CLT connections.

4. Relationship between buck electrical resistivity and drying shrinkage in cement paste containing expansive agent and mineral admixtures

Journal of Building Engineering, Volume 39, July 2021, 102261

Abstract

The buck electrical resistivity, drying shrinkage, mass loss rate and compressive strength are investigated in cement-based materials at early age with a fixed water-binder ratio and constant expansive agent content, considering the effects of different fly ash and slag replacements of cement. Moreover, microstructure of the matrix was analyzed by scanning electron microscope (SEM). The results showed that the specimens with fly ash presented higher buck electrical resistivity and mass loss rate and lower drying shrinkage, due to their loose structure and large expansion behavior generated by more ettringite crystals. Two stages in buck electrical resistivity and three stages in drying shrinkage were defined according to the continuous cement hydration and water evaporation. A natural logarithm relationship between buck electrical resistivity and drying shrinkage in cement paste was constructed. Therefore, electrical response measurement can be applied to characterize the drying shrinkage behavior of cementitious materials.

5. Effect of cellulose pulp fibres on the physical, mechanical, and thermal performance of extruded earth-based materials

Journal of Building Engineering, Volume 39, July 2021, 102259

Abstract

Due to the growing concerns of deforestation, renewable materials as recycled cellulosic waste and non-wood fibres provide an alternative solution for partial replacement of wood resources as a reinforcement agent in building material. This study examined the effect of cellulose pulp inclusion on the physical, mechanical, and thermal performance of extruded cement stabilized earth-based matrices. Laboratory experiments of earth-based matrices reinforced with two types of fibres (bamboo pulp and recycled waste carton pulp) at varying fibre contents (0, 5, 7.5 and 10 %wt.) were performed. The results show that the inclusion of recycled waste carton pulp fibre in the soil matrix significantly improved the performance of the composites compared to matrices reinforced with bamboo pulp fibre. Addition of recycled waste carton pulp displayed improvement in flexural strength (56%), in toughness (733%), and in thermal insulation (36.35%) compared to the control sample. Inclusion of recycled waste carton pulp in earth-based matrix increases the moisture loss, the drying shrinkage and behaves as a water reservoir for earth-based materials. It has been concluded from this study that recycled waste carton pulp has the potential as a suitable reinforcement for the promotion of lightweight earthen wall block materials (reduction of bulk density up to 21% after the inclusion of 10% of recycled waste carton pulp), where flexural strength, ductility, and thermal insulation performance are the primary requirements. In addition, the successful replacement of virgin bamboo pulp fibres with recycled waste carton pulp fibres reduces the environmental footprint of the building material. Therefore, the use of this recycled waste carton pulp in the construction industry will be an attractive alternative as it will solve both energy and environmental concerns.

6. Prioritization of sustainability dimensions and categories for residential buildings of tropical climate: A multi-criteria decision-making approach

Journal of Building Engineering, Volume 39, July 2021, 102262

Abstract

Green Building Rating Systems (GBRS) are widely acknowledged in the building industry towards achieving sustainable development. Initially developed GBRS were often criticized for not being holistic and region-specific. Hence, many researchers are involved in developing a holistic system incorporating environmental, social and economic dimensions of sustainability respecting the requirements of specific countries. However, limited studies exist, considering the region-specific needs, especially in a country like India with a diversified climatic setting within. Therefore, the current study attempts to establish a hierarchy tree for assessing sustainability, focusing on residential buildings of the tropical climatic region of India. An in-depth review of GBRS and published literature succeeded by expert interviews established the hierarchy tree with eleven categories classified under three basic sustainability dimensions. Further, the perception of stakeholders was recorded and the collected data was analyzed using the Fuzzy Analytic Hierarchy Process (FAHP) to determine the priority weight of sustainability dimensions and categories. The stakeholders perceived approximately equal weight for all the three dimensions with slightly higher weight for the environmental dimension. The results also highlight the relevance of the social and economic dimensions in a developing country like India. The categories ‘Energy efficiency’ and ‘Environmental quality and well-being’ received the highest weight under environmental and social dimensions, respectively. The hierarchy tree proposed would remain as a reference for assessing building sustainability in the tropical climate. Moreover, the methodology proposed would serve as a base for developing other region-specific systems.

7. A systematic review of emerging technologies in industrialized construction

Journal of Building Engineering, Volume 39, July 2021, 102265

Abstract

Industrialized construction, because of its factory-based nature, has significant potential for successful adoption of emerging technologies compared to traditional construction. The main objective of this review is to identify the current mainstream research directions and research gaps in applying emerging technologies in industrialized construction. This review classifies and analyzes 102 relevant articles published in the construction management-related journals in the last 15 years (i.e. 2004-2019) according to technology types, structural systems, project phases, and application fields. Results indicate there are apparent differences in the utilization level of different technology types, the research focus for different project phases, and the number of articles for different structural systems. Major benefits and challenges for different application fields are also discussed. This review identifies several research gaps, including less focus on specific structural systems or technologies, inadequate research on performance assessment measures, and a lack of effective training programs. Significantly, this review provides a roadmap for future research, with specific short-term and long-term solutions to address the identified research gaps.

8. Sustainable development of ultra high performance concrete using geopolymer technology

Journal of Building Engineering, Volume 39, July 2021, 102267

Abstract

This paper presents the investigation on the adoption of reaction powder concrete (RPC) concept in geopolymer concrete (GPC) technology to develop ultra high performance concrete (UHPC). Ultra high performance geopolymer concrete (UHPGPC) was developed by completely eliminating Portland cement (PC) with industrial by-products such as ground granulated blast furnace slag (GGBFS) and silica fume (SF) activated with sodium hydroxide (NaOH) and sodium silicate (Na₂SiO₃) solution. The fresh (flow) and mechanical (compressive strength) properties of the mixes with varying replacement level of GGBFS with silica fume, river sand with quartz powder and the inclusion of steel fibres were investigated. The results infer that the inclusion of silica fume, quartz powder and steel fibres has a momentous role on the strength development of the UHPGPC mixes. Additionally, statistical analysis has been carried out by design of experiments using response surface methodology. The ecological parameters were also assessed with the aid of embodied energy and carbon dioxide emission and the results were compared. From the results, it has been inferred that the analytical results were well correlated with the experimental results and the ecological parameters were also less compared to the cement concrete mixes and terms it to be sustainable production.

9. Stress-cognizant 3D printing of free-form concrete structures

Journal of Building Engineering, Volume 39, July 2021, 102221

Abstract

3D printing enables engineers to design and manufacture geometrically complex structures. As 3D printing technology affords design freedom, it also brings along new challenges. One common property of classical 3D printing is the anisotropy arising from the filament-wise 3D printing process. This anisotropy reduces the load bearing capabilities of the 3D printed part when loaded in its weaker axes, that is the directions orthogonal to the filament. Conversely, by designing the 3D printing path through analyses of its mechanical constraints, the 3D printed part may be strengthened and printed such that it carries the majority of the load in its strongest axis, parallel to the filament (T1), thereby increasing its load-carrying capabilities. We experimentally investigated this idea by designing and printing several concrete samples following two strategies: (i) the classical strategy consisting of parallel rectilinear paths irrespective of the load distribution, and (ii) our proposed strategy consisting of paths that are as much parallel as possible to the principal stress lines. We then subjected the samples to mechanical testing. The test results confirmed that the proposed printing strategy significantly improved mechanical characteristics. Cracking patterns were also observed and discussed.

10. Study on aggregate interlock behavior of pre-cracked recycled aggregate concrete without stirrups

Journal of Building Engineering, Volume 39, July 2021, 102257

Abstract

In this study, experiments on pre-cracked push-off specimens without stirrups were conducted to analyze the aggregate interlock behavior of recycled aggregate concrete (RAC). The major variables considered in this study were the surface roughness, recycled coarse aggregate (RCA) replacement ratio, concrete strength, aggregate particle size and loading rate. Experimental results indicate that the roughness of the fracture surface relating to the ratio of aggregate fracture significantly affects the shear stress of pre-cracked push-off specimens. The findings reveal that the RCA replacement ratio has adverse effects on the macro-roughness and the aggregate interlock behavior of RAC. The increasing concrete strength leads to a decrease in the surface roughness and the aggregate interlock capacity of RAC. The inferior properties of RCA contribute to decreasing the aggregate interlock behavior of RAC specimens with larger RCA particles. The influence of the loading rate on the aggregate interlock behavior of RAC is insignificant with the increase from 0.06 mm/min to 0.6 mm/min.

11. Predicting carbonation coefficient using Artificial neural networks and genetic programming

Journal of Building Engineering, Volume 39, July 2021, 102258

Abstract

Concrete carbonation is considered an important problem in both the Civil Engineering and Materials Science fields. Over time, the properties of concrete change because of the interaction between the material and the environment and, consequently, its durability is affected. Conventionally, concrete carbonation depth at a given time under steady-state conditions can reasonably be estimated using Fick’s second law of diffusion. This study addresses the statistical modelling of the concrete carbonation phenomenon, using a large number of results (827 specimens or samples, i.e. 827 is the number of data concerning the measurement of the carbonation coefficient in concrete test specimens), collected in the literature. Artificial Neural Networks (ANNs) and Genetic Programming (GP) were the Soft Computing techniques used to predict the carbonation coefficient, as a function of a set of conditioning factors. These models allow the estimation of the carbonation coefficient and, accordingly, carbonation as a function of the variables considered statistically significant in explaining this phenomenon. The results obtained through Artificial Neural Networks and Genetic Programming were compared with those obtained through Multiple Linear Regression (MLR) (which has been previously used to model the carbonation coefficient of concrete). The results reveal that ANNs and GP models present a better performance when compared with MLR, being able to deal with the nonlinear influence of relative humidity on concrete carbonation, which was the main limitation of MLR in modelling the carbonation coefficient in previous study. ANNs are commonly seen as a black box; in this study, an attempt is made to address this issue through Knowledge Extraction (KE) from trained weights and biases. KE helps to understand the influence of each input on the output and the influences identified by the KE technique are in accordance with general knowledge.

12. Ventilation of buildings with heat recovery systems: Thorough energy and exergy analysis for indoor thermal wellness

Journal of Building Engineering, Volume 39, July 2021, 102255

Abstract

This work analyses deeply and critically the behavior of a heat recovery device of the ventilation system, in a dwelling of the Basque Country, under the energy and the exergy point of view. The aim is to show the different results that come from both perspectives. Heating period was monitored and data of the velocities and temperatures of the extracted and renovation airflows have been registered. With the data recorded, the effectiveness, energy efficiency and exergy efficiency of the recovery system have been calculated. Later, energy savings, primary energy savings and economic savings have been evaluated. Besides, the minimum difference between the outdoor and the indoor temperatures, from which the operation of the recovery system achieves a primary energy saving, an economic saving or an exergy saving were calculated. In addition to the exhaustive monitoring, the concentration of carbon dioxide in each room of the dwelling has been measured. The results obtained show the convenience of using ventilation systems with heat recovery from an energy point of view (with an energy efficiency of 89%), but not so if an exergy analysis is performed (with an exergy efficiency of 4%). After all, Second Law perspective penalizes a lot the electricity consumption for heating purposes, requiring a temperature differences (between the indoor and outdoor temperatures) higher than 32 °C in order to obtain exergy savings (not so under the energy perspective, where a difference of 1.6 °C is enough for having savings). The indoor air quality analysis confirms the adequacy in terms of CO₂ concentration. This work is pioneer in terms of deep exergy application for ventilation systems.

13. Effect of space layouts on the energy performance of office buildings in three climates

Journal of Building Engineering, Volume 39, July 2021, 102198

Abstract

Numerous studies have shown that architectural design affects energy performance significantly. However, the effect of space layouts on building energy performance has not been fully analysed. In this paper, we aim to study the effect of space layouts on energy performance. An office building was used as the reference, and 11 layout variants were proposed and compared for energy performance. Three climates (temperate, cold and tropical) were inspected, with three typical cities (Amsterdam, Harbin and Singapore). Dynamic simulation was conducted for the energy performance assessment integrating daylighting simulation with energy simulation. For each layout, two situations were simulated: one has no shading system, and the other one has an exterior screen for shading. Based on the simulation results, it is found that lighting demand is affected the most by the layout variance, and the resulting maximum difference (difference divided by the highest demand) happens in Harbin, being 46% without shading and 35% with shading. Regarding the sum of the final energy for heating, cooling and lighting, using a heat pump system, the maximum difference is 8% for the layouts both without and with shading system occurring in Amsterdam.

14. Thermal performance of additively manufactured polymer lattices

Journal of Building Engineering, Volume 39, July 2021, 102243

Abstract

The energy performance of buildings is a key point to achieve the sustainability goals of the modern world. The reduction of the heat loss by incorporating porosity in a monolithic material was studied. To this aim, lattice structures with varying lattice topology and specimen size were synthesised using polymer based additive manufacturing. Commercially available 3D printers and polymer filaments were utilised to manufacture such polymer lattices. Their thermal performance was characterised using a bespoke compact temperature-change hot chamber. A scaling law, based on the experimental results, has been proposed for the first time to predict the U-value of polymer lattices by correlating their effective thermal conductivities. It was observed that the lattice’s relative density and the sizes of a unit cell and specimen affected significantly the U-value. Also, it was found that polymer-lattice structures can be designed to only allow a conductive mode of heat transfer when their hydraulic diameter was less than 8 mm. The effect of an AM process parameters such as the layer thickness and type of 3D printer on the U-value of the polymer lattices was also characterised and found that they had a mild effect on the U-value of the lattices. Thus, a highly optimised lattice structure, aiming at achieving the higher thermal resistance to make it suitable for energy saving applications, can be obtained using the proposed scaling law.

15. Sound insulation of gypsum block partitions: An analysis of single and double walls

Journal of Building Engineering, Volume 39, July 2021, 102253

Abstract

This paper presents an evaluation regarding the sound insulation of simple walls built with gypsum blocks, both solid and hollow, with different thicknesses and densities, and double walls with and without acoustic absorbent material. Currently, the sound reduction index (R) is one of the parameters used in residential building projects in Brazil, since it is of fundamental importance for predicting acoustic insulation in the field, a requirement recommended by the Brazilian performance standard ABNT NBR 15575 [1], in line with international standards. Gypsum blocks are elements commonly used in the internal vertical partitions of buildings, in Europe and especially in Brazil. In this paper, the sound reduction index of 22 partitions was analyzed by conducting tests in a standardized laboratory. The results show that, above 70 kg/m², hollow gypsum blocks tend to demonstrate greater acoustic efficiency than solid blocks. The critical frequency of the single walls was analyzed; these values theoretically calculated for the solid gypsum blocks are within the frequency range obtained experimentally. The double walls without acoustic absorbent material showed similar efficiency, regardless of the air gap. Double walls with acoustic absorbent material are more efficient and this varies depending on what materials, such as glass wool and PET wool, are placed in the same space between the walls. It is still very rare for the literature to report laboratory data regarding the acoustic performance of the gypsum blocks used in this paper and therefore our doing so is a significant contribution to this field of study.

16. Impacts of design deficiencies on maintenance cost of high-rise residential buildings and mitigation measures

Journal of Building Engineering, Volume 39, July 2021, 102215

Abstract

The building design has drawn great attention in recent years because of its large impact on many aspects of the functionality and maintenance activities in high-rise residential buildings (HRRB). These buildings include innovative and exciting design solutions that increase project complexity and produce substantial unexpected design deficiencies. Therefore, the aim of this study was to identify and examine the design deficiencies’ impact on maintenance cost and investigate the mitigation strategies in reducing this cost. To fulfill the aim of this study, 42 design deficiencies and 11 mitigation measures were identified through a comprehensive literature review. This was followed by a questionnaire that was developed and administered to collect data, and 118 respondents graded the identified design deficiencies and mitigation measures using a five-point Likert scale during this online survey. Then the ranking analysis was done utilizing mean value and standard deviation (SD). The analysis revealed that architectural design deficiencies group has the most impact on increasing maintenance cost. Among 42 design deficiencies, only 23 were recognized as critical design deficiencies (CDD). Kruskal–Wallis analysis of variance (ANOVA) test result showed that statistically insignificant differences in rankings were observed for two design deficiencies: non-availability of specific building materials in the market and difficult to reach and maintain fenestration. The Mann-Whitney test revealed that the building supervisors and facility managers had different opinions for these two design deficiencies compared to three other groups of the respondents. Furthermore, applying the factor analysis technique, 23 CDD were categorized into six groups: poor quality of design, inaccessibility for maintenance work, inappropriate material selection, lack of designer’s responsibility, lack of designer’s experience, and improper design scheme. Finally, the relationships between the 23 CDD and the mitigation measures were identified using the Spearman correlation test. This study is worthy of industry-wide attention and its implementation can be greatly advantageous for the construction industry professionals.

17. Smart building management system: Performance specifications and design requirements

Journal of Building Engineering, Volume 39, July 2021, 102222

Abstract

In a smart building, physical and computational elements are integrated to create an environment that is energy-efficient, comfortable, and safe for its occupants. The design and development of smart buildings is a complicated task. Every smart building is a unique structure from the requirements and characteristics standpoints. Therefore, achieving reliability and real-time adaptation to environmental conditions are some of the challenges involved in smart building development. Resolving these issues requires deep insights into control theory, machine learning, system specifications, and design requirements. To address this need, this paper proposes a real-time management system for controlling various aspects of smart buildings (indoor conditions, comfort criteria, security, safety, and costs), and also presents the performance specifications, design requirements, and operating constraints for these systems. The study aims to address two less-attended problems in the related literature of building management and control. First, only a few studies have attempted to include real-time learning of buildings’ subjective parameters in the model-based control design. Second, to the best of the authors’ knowledge, smart building management studies are primarily focused on optimizing thermal or visual aspects of buildings, and little attention is given to the simultaneous management of all building subsystems and objectives; i.e., considering buildings’ physical models, environmental conditions, comfort specifications, and occupants’ preferences and safety in the design. Accordingly, in this paper, we combine machine learning with model-based control approaches to incorporate subjective environmental parameters into the building management structure. In addition, another benefit of this study is that it integrates model-based and learning-based control schemes in a unified management structure for controlling various aspects of building performance. The proposed building management system can be applied to a variety of smart buildings in which the building parameters can be monitored and self-tuned using a well-defined set of control inputs.

18. Integrated implementation of Virtual Design and Construction (VDC) and lean project delivery system (LPDS)

Journal of Building Engineering, Volume 39, July 2021, 102252

Abstract

Lean project delivery system (LPDS) has proven to be an effective productivity improvement method. Despite enormous benefits, the construction industry is struggling with effective implementation of LPDS especially in achieving Lean construction (LC) principles like improving the visualization and maintaining effective flow of information. Concurrently, Virtual design and construction (VDC) has opened new windows of opportunities for the construction industry through multidisciplinary integration of design, and construction processes and improving automation through visualization. Using the potentials of VDC to effectively implement LPDS is an area scarcely examined in the current body of knowledge. This study identifies implementation potential of LPDS integrated with VDC, and develops implementation steps to effectively utilize VDC functionalities within the Lean environment using a systematic literature review (SLR) process. The common links between VDC and LDPS are identified through review of academic and practice-based literature. Using a matrix in which potential benefits of VDC are analyzed based on their synergistic impact on Lean principles, a total of 351 positive hypothetical interactions were found between LC and VDC, displaying a strong synergy between them. Moreover, based on the literature, 65 opportunities associated with VDC that support LPDS implementation are identified. Apart from the support by VDC, six (6) areas where Lean intervention can mitigate the challenges faced by VDC are identified. In the end, proposed implementation steps for utilizing VDC within the LPDS environment have been developed. This novel study will help the construction industry improve performance through simultaneous application of LPDS and VDC.

19. Evaluation of the influence of accelerated carbonation on the microstructure and mechanical characteristics of coconut fibre-reinforced cementitious matrix

Journal of Building Engineering, Volume 39, July 2021, 102269

Abstract

In this study, two methods were used to measure the carbonation depth of coconut fibre-reinforced mortars that were prepared from Portland cement (PC) and calcium sulfoaluminate cement (CSA cement), including traditional phenolphthalein reagent and thermogravimetric analysis (TGA). Accelerated carbonation was conducted at 4% CO₂ concentration, temperature of 20 °C and 65% relative humidity (RH) within 12 weeks. Complete carbonation was detected in the CSA cement-based mortar while PC-based mortar was carbonated partially according to both methods used. The difference in carbonation depth, however, is observed as soon as the reagent and TGA measurement were applied. The significant effectiveness of the carbonation process on the microstructure changes and mechanical characteristics of the cementitious matrix is highlighted through analysis of the change in the quantity of calcium carbonate (CC) and portlandite (CH) on the different mortar profiles and comparison with natural cured samples.

20. Online model for indoor temperature control based on building thermal process of air conditioning system

Journal of Building Engineering, Volume 39, July 2021, 102270

Abstract

Since there are lots of influencing factors in indoor temperature regulation process of air conditioning system in the large-public building, it is difficult to establish an accurate mathematical model and to implement model-based online control. This paper proposes an online modeling method for indoor temperature regulation characteristic according to building thermal process. A physical-data driven model, which takes the state-space equation solution representation form as the reference structure, is proposed, and the model parameters are identified based on the multiple linear regression analysis. Then, experimental and simulation studies in online and offline have been carried out to validate the proposed modeling method. The contribution of this study is to provide an online model, which can not only retain system physical property but also be updated online simply. The proposed model with building thermal process property will be benefit for terminal controller design for indoor temperature regulation in the air conditioning system.

21. Artificial intelligence to design collaborative strategy: An application to urban destinations

Journal of Business Research, Volume 129, May 2021, Pages 936-948

Abstract:

Organisations currently compete within contexts that require collaboration with other players (suppliers, customers, competitors), which is central to achieving sustainable competitive advantages. This new perspective, which is centred on relationships, has changed the way companies design and implement their competitive strategies, while also challenging traditional tools of strategy analysis. Artificial intelligence, particularly artificial neural networks, can help address these challenges. This paper proposes an innovative application of the Auto-Contractive Map method, which is a deep non-supervised Artificial Neural Network algorithm that has already been widely applied to bio-medical, security, insurance, and financial studies, but has not yet been used in the domains of tourism and strategy. Our study demonstrates the effectiveness of this method, compared to other methods that have been applied to tourism studies. This method successfully addresses issues in the complex and dynamic competitive settings of tourism destinations, which are characterised by the inclusion of many stakeholders. Specifically, the Auto-Contractive Map method allows both scholars and practitioners to significantly advance formulations of collaborative strategies in a destination, at three levels: (i) defining priority areas of action, (ii) identifying relevant stakeholders and governance levels that have control over these areas, and (iii) profiling key features of the destination’s positioning, compared with its competitors.

22. Intervention strategies for urban blight: A participatory approach

Sustainable Cities and Society, Volume 70, July 2021, 102901

Abstract:

Urban blight has been the subject of numerous worldwide studies. However, because of blight’s complexity, direct relationship with ​​urban planning and multifaceted associated variables, studies targeting certain aspects of blight require detailed conceptualization and structure to facilitate decision-making processes that address blight. Many urban, socio-economic and cultural externalities associated with blight need to be addressed in developing viable intervention strategies for prevention, attenuation and eradication. Identifying and simplifying the complex issues associated with blight is important as their intricacy creates difficulties for decision makers. We simplify the blight problem by using unique techniques for structuring complex decision problems (i.e., problem structuring methods (PSMs)). This methodology is based on multiple-criteria decision analysis (MCDA) principles, as well as a combination of participatory techniques (i.e., decision conferencing and cognitive mapping). In a subsequent phase, the decision-making trial and evaluation laboratory (DEMATEL) technique is used to enable the development of a more realistic, transparent analysis model for blight intervention strategies. This study assumes a constructivist logic, so both objective and subjective elements are included. The proposed methodology’s advantages and limitations are also discussed.

VẬT LIỆU XÂY DỰNG

1. High temperature resistance of a phase change cementitious material at elevated temperatures

Construction and Building Materials, Volume 292, July 2021

Abstract

When ordinary Portland cementitious concrete is subjected to elevated temperatures, lots of pores and cracks are produced in the cement matrix. In order to solve the problem of pore and crack repairing, a phase change material (PCM) with a melting temperature of 450 °C was prepared in the laboratory. Ordinary Portland cement with addition of the PCM is termed as phase change cementitious material (PCCM). High temperature resistance of PCCM was investigated according to changes in surface morphology, mechanical strength and mass, as well as micro and meso structures of the PCCM matrix at high temperatures of 500 °C,600 °C,700 °C,800 °C and 900 °C. The results show that the compressive strength of PCCM mortar specimens is increased with temperature lower than 600 °C compared with that at room temperature, and that compressive strength loss of PCCM mortar specimens after exposed to 900 °C can be reduced to 48.5%. The PCM in PCCM matrix experience phase changes from solid to liquid phase at elevated temperatures. The melted PCM is able to fill pores and cracks in PCCM matrix. Once the temperature decreases to room temperature, the melted PCM becomes in solid phase again. Pores and cracks in PCCM matrix are thus repaired, resulting in improved microstructure of PCCM compared with that of ordinary Portland cement. Therefore, high temperature resistance of PCCM is much better than that of ordinary Portland cement.

2. Mechanical and structural performance evaluation of pervious interlocking paver blocks

Construction and Building Materials, Volume 292, July 2021

Abstract: Pervious concrete is one among the evolving sustainable pavement materials due to its unique storm water storage and ground water recharge applications. The present study aims to develop a Pervious Interlocking Paver Block (PIPB) and to study its mechanical, functional and structural performance. In the current explorative research work, the influence of aggregate gradation, and the percentage of fines on mechanical, functional and structural performance of PIPB were evaluated. The mechanical and functional properties such as compressive strength, split tensile strength, flexural strength, and skid resistance are assessed. The structural behaviour of the PIPB pavement section is found using plate load test and large-scale direct shear test. FEM based software, PLAXIS, is used to validate the test results. Infiltration test is conducted on the plate load test section to understand the infiltration rate. Finally, 2D image processing was performed using MATLAB to conclude the test findings. The test results proved that the grade III mix possesses desirable mechanical properties, lower deflection, higher shear strength, and required permeability. The present study affirms that the PIPB can be an effective pavement material for the low volume roads, urban heat island and pavements with drainage problems.

3. Performance of fibre-reinforced cementitious composites at elevated temperatures: A review

Construction and Building Materials, Volume 292, July 2021

Abstract

The demand for various types of fibre-reinforced cementitious composites (FRCCs) has increased over the past few years owing to their enhanced performance as a result of denser microstructure and the presence of fibres. However, the effectiveness in preventing mechanical decay and spalling damage on exposure to elevated temperatures has been a concern for FRCC. The results obtained from existing studies on the fire performance of FRCCs differ considerably due to the differences in adopted type of cementitious matrix, fibre types and their dosage, or testing methods. This paper aims to understand the combined influence of such factors and provide an in-depth review of their effects on the performance of FRCC at elevated temperatures. Temperature variation of different mechanical and thermal properties of FRCC and the factors contributing to its spalling resistance are comprehensively discussed and some potential areas for further research have been identified. In addition, available data and existing prediction models on the residual or hot-state mechanical properties of FRCC are also summarized which may be used in future numerical or other computational studies for the fire resistance design of structures.

4. A comparative study on the mechanical properties, autogenous shrinkage and cracking proneness of alkali-activated concrete and ordinary Portland cement concrete

Construction and Building Materials, Volume 292, July 2021

Abstract

This study aims to compare the developments of mechanical properties and autogenous shrinkage related properties of alkali-activated materials-based concrete (AC) and ordinary Portland cement-based concrete (OC) against curing age and degree of reaction. Temperature Stress Testing Machines are utilized to monitor the evolution of the internal tensile stress and the cracking occurrence in the restrained concrete. It is found that AC shows lower tensile strength-to-compressive strength ratios than OC. The mechanical properties of both OC and AC can be modelled by a power law against the degree of reaction. AC shows higher autogenous shrinkage, but later cracking than OC when under restrained condition. However, the degrees of reaction at which AC and OC cracked are very similar. From the autogenous shrinkage, the elastic modulus and the self-induced stress, the elastic and creep deformations of the concrete can be calculated. AC is found to show much higher creep coefficient than OC.

5. Hollow glass microspheres-based ultralight non-combustible thermal insulation foam with point-to-point binding structure using solvent evaporation method

Construction and Building Materials, Volume 292, July 2021

Abstract

Usually, the thermal insulation and flame retardancy of traditional building material are mutually exclusive. It is very challenging to make a material with both of these properties. In this study, a hollow glass microsphere based ultralight non-combustible thermal insulation foam (HGMs-TIF) with point-to-point binding structure was prepared using solvent evaporation method. Five samples were prepared with different mass ratios of hollow glass microspheres and phenolic resin. The results showed that as the mass proportion of HGMs increase from 60.6% to 88.5%, the thermal insulation as well as flame retardancy of composite is improved. Remarkably, the HGMs-TIF-01 which has the largest proportion of HGMs (88.5%) shows lowest thermal conductivity of 0.0452 W/(m∙K) and lowest gross heat of combustion of 2.844 MJ/kg, what implies it is a non-combustible material according to the National Standard of the People’s Republic of China GB/T 8624-2019 (i.e. gross heat of combustion of the standard of class A2 is lower than 3 MJ/kg). Besides, the HGMs-TIF-01 also is a lightweight and high-strength material, which has a low density of 0.142 g/cm3 and a high compressive strength of 0.748 MPa. It is helpful for the further design of the non-combustible thermal insulation material.

6. Micro- and macrocracking behaviors in granite and molded gypsum containing a single flaw

Construction and Building Materials, Volume 292, July 2021

Abstract

The effect of preexisting defects on fracture behaviors is significant for the stability analysis of rock engineering. To study the effect of preexisting flaws on the micro- and macrocracking behaviors of rocks, photographic monitoring together with strain field analysis, passive acoustic emission (AE) and active ultrasonic testing were carried out on gypsum and granite samples containing a single flaw. Based on coupled analysis of the acousto-optic-mechanical characteristics, it is suggested to identify micro- and macrocrack initiation by AE monitoring rather than stress–strain behaviors, photographic observation and P-wave measurement. The micro- and macrocrack initiation stresses generally increase with the flaw angle. The microcrack initiation stress ranging from 0.22σc to 0.62σc (peak strength) coincides with the onset of AE events, and the macrocrack initiation stress ranging from 0.60σc to 0.85σc coincides well with a dramatic increase in AE energy for flawed granite. The crack types are classified into nine different categories. Macrocrack coalescence is observed before reaching σc, and violent rock failure occurs seconds after σc is achieved for flawed granites, which differs from that process for gypsum samples. The cracking process of flawed granites experiences three typical stages and is highly dependent on the flaw angle. A stress drop accompanied by a significant increase in the AE energy rate appears several times. With an increasing flaw angle, the count of stress drop and the cumulative AE energy decrease, while the maximum value of the AE energy rate and the average hit energy increase gradually. The energy and stress release reduces the violent failure degree of rock. The AE energy correlated with the cracking magnitude changes more violently than the AE event before peak failure. P-wave attenuation increases sharply after macrocrack initiation. A sharp reduction in velocity is always accompanied by a significant increase in the AE rate. Compared with the global cracking damage of rock characterized by AE characteristics, the fracture identified by P-wave velocity is localized.

7. Bond behavior of CFRP-concrete bonding interface considering degradation of epoxy primer under wet-dry cycles

Construction and Building Materials, Volume 292, July 2021

Abstract

The excellent performance of the CFRP-concrete bonding interface is a key to ensure the reliability and effectiveness of the rehabilitation in concrete structures with external fiber reinforced polymer (FRP). Meanwhile, the epoxy primer, which bonded the FRP plate and the concrete substrate, is significantly affected by the aggressive environment. In this paper, two kinds of experiments which associated with the CFRP-concrete specimens and the epoxy primer after corroding in a wet-dry cycles environment were conducted. It shows that the immersion area of the epoxy primer has a significant influence on the properties of the moisture absorption, and that would lead to a degradation in the mechanical properties of the CFRP-concrete interface. Simultaneously, the failure modes of the CFRP-concrete interface presented a transformation from the epoxy/concrete interaction layer to the epoxy primer layer along with the increase of aging duration. To further depict the degraded bond behavior, a time-dependent bond-slip model considering the degradation of epoxy primer was proposed, and the interface fracture energy was utilized to quantify the degree of the deterioration. By comparing with the value of interface fracture energy, it was figured out that the normal bond-slip model (Popovics model) is not enough for the safety of the concrete structures rehabilitated with external CFRP, and the proposed time-dependent bond-slip model is more accurate in evaluating the time-dependent mechanical properties of concrete structures suffering in an aggressive environment.

8. Effects of asphalt emulsion on the durability of self-compacting concrete

Construction and Building Materials, Volume 292, July 2021

Abstract

Asphalt emulsion (AE) is the alternative raw material for self-compacting concrete (SCC), some researchers have reported on the composition design, workability, and strength properties recently. But few attempts have be made on the durability. For a better understanding on the effects of AE on SCC durability and its microscopic mechanism, the SCC specimens were prepared with various AE contents, and the self-compacting workability was confirmed via slump flow test. Then, three kinds of durability tests were performed to evaluate the chloride-penetration resistance, frost resistance and sulfate-corrosion resistance, and the scan electronic microscope (SEM) test and X-ray diffraction (XRD) test were performed to discuss the microscopic mechanism. The results show that the chloride-penetration resistance, frost resistance and sulfate-corrosion resistance of SCC were enhanced by adding AE. Observed from SEM test, the interfacial transition zone (ITZ) of SCC is mainly filled with the C-S-H gel and AE, and the SCC microstructure tends to be compact, resulting that the concrete durability was improved by using appropriate AE. However, the excessive AE may lead to more pores in SCC because of the retardation effect on cement hydration. The AE with the content of 10% given the most desirable effect for durability.

9. A critical review on the use of copper slag (CS) as a substitute constituent in concrete

Construction and Building Materials, Volume 292, July 2021

Abstract

In recent decades, CO2 emissions from concrete production account for 5% of the global total carbon emissions. At the same time, the amount of industrial waste is also increasing year by year. As a non-toxic and harmless industrial waste, copper slag (CS) has been a great concern for researchers as a type of building material in recent years. This paper mainly reviews the relevant literature published in the past decade; critically discusses the performance of CS and the influence of partial replacement of CS on performance; and performs a global analysis, pointing out the direction for the future research on CS concrete. To make the conclusion comprehensive and reliable, this paper has consulted more than 90 related studies. The fresh performance, mechanical property and durability of CS concrete are discussed from three aspects of particle size, replacement rate and replacement method. In conclusion, as a partial replacement of cement or aggregate in concrete, CS can appropriately improve the strength, chloride ion corrosion resistance, sulphate corrosion resistance, carbonation resistance and freezing–thawing resistance of concrete. On the basis of research that describes the durability and compressive strength of CS concrete, the particle size and replacement ratio of CS in concrete preparation should be below 10 mm and 40%, respectively. According to the environmental impact analysis, using CS as a partial substitute can improve the environmental impact, although the production process still needs to be improved. Global analysis of results indicates that the long-term mechanical properties and durability of CS concrete need to be further studied.

10. Impact of polycarboxylate superplasticizers (PCEs) with novel molecular structures on fluidity, rheological behavior and adsorption properties of cement mortar

Construction and Building Materials, Volume 292, July 2021, 123285

Abstract: Polyether macromonomers have shown diversified structures recently. In this work, a series of polycarboxylate superplasticizers (PCEs) were synthesized via copolymerization using a novel macromonomer, ethylene–glycol monovinyl polyethylene glycol (EPEG). The molecular structures were modified by varying the side chain length, carboxylate density and integrating sulfonic group. The synthesis reaction of PCEs with high reaction conversion ratio was achieved through rapid reaction(20–30 min) at low temperature (5-20℃). The fluidity of PCEs, the rheological parameters and the compressive strength of mortar were measured. The adsorption behavior and zeta potential of the cement particles were also measured. Results have shown that PCEs with short side chain and high carboxylate density had high adsorption ability, high dispersion capacity in mortar. In addition, PCEs with sulfonic group had increased adsorption amount on the cement surface. These results could allow further progress in the application of EPEG macromonomer.

11. Sustainable utilization of biomass waste-rice husk ash as a new solidified material of soil in geotechnical engineering: A review

Construction and Building Materials, Volume 292, July 2021, 123219,

Abstract

Nearly 150 million tons per year of waste rice husks are produced worldwide and get accumulated due to underutilization. These waste rice husks have caused serious environmental problems. Transforming rice husks into rice husk ash (RHA) and applying into engineering practice contributes to the sustainable recycling of biomass waste. This paper summarized the basic characteristics of RHA and its application in chemical industry, building materials, environmental protection, especially in geotechnical engineering. A comprehensive review of literature available on RHA-soil mixture was performed to identify the gaps in understanding the behavior of the mixture in terms of mechanical properties, durability, environmental impact and internal mechanism. The results showed that the addition of RHA can effectively improve the performance of soil related to shrinkage cracking, and significantly enhance the compressive strength, shear strength and CBR value of the soil, indicating economic and environmental benefits. Overall, the comprehensive utilization of RHA in geotechnical engineering as a partial alternative of cement/lime is promising as it can contribute to energy savings, low-carbon emissions and sustainable development. However, the acquisition of higher active RHA, micro mechanism of RHA-soil, and in complex environment, the durability, deterioration mechanism and environmental impact of RHA treatment on soil mixtures still need to be studied further.

12. High flexural strength and durability of concrete reinforced by in situ polymerization of acrylic acid and 1-acrylanmido-2-methylpropanesulfonic acid

Construction and Building Materials, Volume 292, July 2021, 123428,

Abstract

Brittleness of the normal concrete has an adverse effect on its application in structures undertaking the bending load. In the current study, concrete was modified by in situ polymerization of acrylic acid (AA) and 1-acrylanmido-2-methylpropanesulfonic acid (AMPS) during cement hydration to strengthen their flexural strength and durability. By adding 7 wt% of AA-AMPS to the concrete, the flexural strength of concrete showed an increment of 61.2% in comparison to the reference one, which was attributed to the polymerization reaction of AA-AMPS monomers that took place at the early stage of the cement hydration, and the rapid formation of polymer network could also densify and compact the interfacial transition zone (ITZ) in the cement matrix. The water and chloride resistances were also enhanced with the increased amount of AA-AMPS. In conclusion, this strategy has great potential to develop high performance concrete with enhanced flexural properties and durability.

13. Effect of application of metallurgical slag powders on physical and rheological properties of asphalt

Construction and Building Materials, Volume 292, July 2021, 123432

Abstract

Metallurgical slags are residues that are obtained in the manufacturing and smelting processes of metals, such as steel and copper. However, their use is limited because they may cause environmental problems at their disposal sites. This study aims to evaluate the effects of the addition of slag on the properties of slag-modified asphalts using three different slag proportions (3, 6, and 10% by weight of asphalt). Electric arc furnace slag, blast furnace slag, and copper slag were used to evaluate the effects of the addition of slag on their performance properties via physical and rheological tests. The results showed an improvement in the consistency of the slag-modified asphalts, decreasing the penetration rate and increasing the softening point. An enhancement in the short-term asphalt aging characteristics was also observed with the addition of slag. Finally, the rheological test results revealed an improvement in the resistance to permanent deformation with the addition of slag in neat asphalt, whereas no statistically significant results were observed when the slag content was increased.

14. Compressive strength prediction models of lightweight aggregate concretes using ultrasonic pulse velocity

Construction and Building Materials, Volume 292, July 2021, 123419,

Abstract

Replacement of natural coarse aggregate with lightweight aggregate (LWA) offers not only the specific properties of concrete such as thermal, acoustic properties, or lighter weight concrete but is also dealing with wasted materials recycling and natural resources depletion. Ultrasonic pulse velocity (UPV) is closely correlated to both mechanical and physical properties of concrete and it is introduced and used to predict the compressive strength of concrete structures. This paper proposes two prediction models for compressive strength of lightweight aggregate concrete, a regression model and a back-propagation neural network (BPNN) incorporating UPV for different accuracy requirements. The regression model is a further generalised regression model for estimating compressive strength from UPV of lightweight aggregate concrete (LWAC) that can be adapted to different testing systems. The BPNN model, optimised by a genetic algorithm, is also employed for more accurate predictions compared to the regression model. To achieve this, a database which comprises a total of 603 sets of data from 26 different studies was compiled. In addition, the database also involves wide ranges of sizes of coarse aggregates (4 mm – 40 mm) and LWAs (0.65 mm – 30 mm), volume ratios of coarse aggregate to binder (0.53 – 9.66) and sand to aggregate (0 to 5.99), LWA volume fraction (0 – 100%), water to binder ratio (0.3 – 0.89), and curing time (1 day to 120 days). Statistical results indicate that regression model and BPNN model can produce a reasonable estimation of compressive strength for lightweight aggregate concrete but with different accuracy level. Hence, the two proposed models can be used to adapt to different expectations of accuracy in different situations.

15. Cost-effectiveness evaluation of pavement maintenance treatments using multiple regression and life-cycle cost analysis

Construction and Building Materials, Volume 292, July 2021, 123461

Abstract

The present study compared the effectiveness and cost-effectiveness of four pavement treatments, including hot in-place recycling, milling and filling, thin HMA overlay and microsurfacing. The multiple regression analysis was employed to investigate the effectiveness of treatments and the effect of pretreatment rutting severity and traffic conditions on maintenance effectiveness. The rutting depth (RD) was selected as a performance indicator. The reduction of RD degradation rate and increase in average RD over monitoring period were used as measures of treatment effectiveness. Life-cycle cost analysis was performed to evaluate the treatment cost-effectiveness over a 50-year analysis period. Results indicate that the hot in-place recycling possesses the highest effectiveness and cost-effectiveness. Using reclaimed asphalt pavement (RAP) at appropriate maintenance timing substantially benefits for restoring the rutting resistance of asphalt pavement. These findings provide project agencies with quantitative evidence to support the establishment of the rutting-based maintenance decision-making system and the utilization of RAP in the sustainable pavement management strategies.

16. Reutilisation of hazardous spent fluorescent lamps glass waste as supplementary cementitious material

Construction and Building Materials, Volume 292, July 2021, 123424

Abstract

Spent fluorescent lamps glass (SFLG) waste, manually and mechanically processed in a lamps waste treatment plant, was used to partially replace up to 50 wt% Portland cement (PC). Both waste types exhibited similar pozzolanic activity. The mortars containing up to 35 wt% SFLG met the specifications for other pozzolanic materials (e.g. fly ash) and, after 90 curing days, their compressive strength values were similar to or higher than those of the 100% PC sample (58.8 MPa). Our results provide an alternative reutilization process for this hazardous waste to reuse SFLG as-received (no washing to reduce mercury) and contributes to less PC use.

17. Enhanced toughness of ultra-fine sulphoaluminate cement-based hybrid grouting materials by incorporating in-situ polymerization of acrylamide

Construction and Building Materials, Volume 292, July 2021, 123421,

Abstract

Deep coal mining requires grouting reinforcement materials with adjustable setting time, high early strength and toughness. Sulphoaluminate cement-based grouting materials (SCGM) have been widely used due to their low cost, but still suffer from poor deformation and toughness. To solve this problem, in-situ polymerization of acrylamide was developed to modify SCGM, and the effects of acrylamide addition on the fluidity, setting time, mechanical properties, and microstructure evolution of SCGM were systematically investigated. The results indicated that the addition of acrylamide significantly improved the toughness of SCGM. When the acrylamide content reached 35 wt%, the flexural strength of SCGM increased to 10 MPa and the compressive strength reached 35 MPa. In light of microstructural analysis, the exothermic heat of SCGM hydration promoted the free radical polymerization of acrylamide to form inorganic–organic hybrid grouting material with a three-dimensional interpenetrating network structure, which was responsible for the enhanced toughness of SCGM. Those results provided a new method to enhance the toughness of SCGM, making it more suitable for grouting reinforcement engineering.

18. Microstructural investigation of slag-blended UHPC: The effects of slag content and chemical/thermal activation

Construction and Building Materials, Volume 292, July 2021, 123455,

Abstract

This paper focuses on the microstructural investigation of ultra-high performance concrete (UHPC) mixtures featuring various replacement levels for blast furnace slag (BFS), in the aim of becoming more environmentally-friendly. Three levels of slag are applied (namely 30%, 50% and 80%) per unit volume of cement. The microstructural characteristics examined included X-ray diffraction (XRD) analysis, transmission electron microscopy (TEM), and mercury intrusion porosimetry (MIP). These characteristics are assessed along with the mechanical strengths at 3 and 90 days. Similarly, the effects of chemical and thermal activation methods on incorporating BFS into UHPC mixtures at high volumes were studied from a microstructural point of view, and a comparison is drawn between the non-activated and activated mixtures. The results of this investigation show that the beneficial physical impact of slag replacement lies at the 30% level, due to its filler property in stimulating hydration to quickly generate portlandite. For this reason, the portlandite and C-S-H peaks are quite similar to those in the reference mixture (i.e. 0% BFS) at 3 and 90 days, as demonstrated in the XRD analysis. Moreover, the pore size distribution could be refined, the microstructure densified (as indicated on the TEM images), and compressive strengths at both ages improved. In contrast, for slag replacement levels of 50% and 80%, the portlandite and C-S-H peaks are significantly lowered, as observed in the XRD analysis, thus causing a magnification of the capillary pores and a drop in compressive strength at 3 and 90 days. Chemical activation through a potassium hydroxide, with a dosage of 10.17 kg/m3, at the 80% BFS replacement level is able to accelerate hydration and portlandite consumption, as exhibited in the XRD analysis through the absence of portlandite peaks and limited quantities of C-S-H at 3 and 90 days. However, this step results in smaller pores and a higher compressive strength. As for the thermal activation, the portlandite in the blended mixtures with 50% and 80% BFS replacement decreases in quantity, as confirmed by XRD analysis, and the reaction is perfectly activated by means of the solubility acceleration of the alkalis; consequently, the pore structure is compacted, as revealed on the TEM image and the compressive strength rises considerably.

19. Effect of aging on fatigue performance of cement emulsified asphalt repair material

Construction and Building Materials, Volume 292, July 2021, 123417,

Abstract

Cement emulsified asphalt repair material (simplified as CEA repair material) is a composite material formed by hardening of cement and cementation of emulsified asphalt. The aging performance and fatigue performance of CEA repair material will affect the repair effect of cracks. In this paper, the effect of aging on fatigue performance of CEA repair material was studied through the fatigue tests after aging. The fatigue equation and the fatigue damage evolution equation considering the aging effect were established. The effects of aging time, stress ratio and material ratio on the fatigue performance of CEA repair material were analyzed. As the aging time increases, the fatigue life of CEA repair material decreases, and the sensitivity of fatigue life to the change of stress ratio decreases. The increase of cement content can reduce the aging degree of asphalt and slow down the aging speed of asphalt. The increase of cement content can also improve the stability of fatigue performance of CEA repair material. The effect of stress ratio on fatigue life is related to aging time and material ratio. As the aging time increases, the phase angle decreases and the energy dissipation decreases. Increasing the amount of cement can improve the stability of fatigue performance of CEA repair material, but it reduces the fatigue life of CEA repair material. The material design of CEA repair material should comprehensively consider the aging resistance and fatigue performance, and rationally determine the amount of cement and emulsified asphalt.

20. Chemically resistant polymeric jointing grout with environmental impact

Construction and Building Materials, Volume 292, July 2021

Abstract: This paper deals with the study of the chemical resistance of polymeric jointing grouts intended for the jointing of elements that are permanently stressed by an aggressive chemical environment, such as elements made of cast basalt, placed in the concrete structures of sewerages. The paper researches three types of epoxy jointing grouts designed for conditions where there is a chemically aggressive environment. The optimal amount of hazardous waste (end product and cement bypass dusts) was incorporated in the developed jointing grouts. As part of chemical resistance monitoring, changes in selected physical and mechanical properties of jointing grouts were monitored and evaluated, including microstructure monitoring after chemical stress. The scanning electron microscopy (SEM) was used for the explanation of bonding effects of the polymer matrix with the filler It was found that the use of hazardous waste is highly effective in polymeric grouts with high chemical resistance; there was no noticeable reduction in the chemical resistance of these jointing grouts compared to the reference grouts.