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Substantial amount of resources is consumed by pavement systems, which have resulted considerable environmental impacts. Understanding the environmental impacts would provide opportunity for reducing resource consumption and informing decision-makers in the process of designing sustainable pavement. There is a lacking of comprehensive and comparative sustainability assessment of pavement systems in highly urbanized context currently. Therefore, this study aims to design and comprehensively evaluate the environmental performance of the commonly adopted pavement systems in highly urbanized context using lifecycle assessment (LCA) technique through a case in Hong Kong. According to the codes and practices of Hong Kong, two pavement systems including flexible and rigid pavements were designed based on the same road section. After that interviews with structured questionnaire were conducted to collect relevant practical information of pavement construction and maintenance from the relevant professional bodies and experts for the subsequent LCA of such designs. The LCA results reveal that the two mid-point impacts of global warming potential and mineral extraction are 21% and 54% higher for rigid pavement than for flexible pavement. Yet, the end-point results indicate that flexible pavement is associated with 64%, 65%, and 69% higher human health impact, ecosystem quality damage, and resource damage, respectively. Material production and transportation contribute significantly to the total impact in the two pavement systems. For instance, it is about 57% and 97% of the total global warming potential for flexible and rigid pavements, respectively. The overall results demonstrated that 49% higher total impact was found for flexible pavement than rigid pavement. Therefore, the use of more recycled and environmentally friendly materials can potentially enhance the environmental sustainability of both pavement systems. The findings should provide useful information to the design and selection of sustainable pavement structures in resource-scarce highly-urbanized cities., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

With the promotion of environmental protection in the construction industry, the mission to achieve more sustainable use of resources during the production process of concrete is also becoming important. This study was conducted to assess the environmental sustainability of concrete slurry waste (CSW) management by life cycle assessment (LCA) techniques, with the aim of identifying a resource-efficient solution for utilisation of CSW in the production of partition wall blocks. CSW is the dewatered solid residues deposited in the sedimentation tank after washing out over-ordered/rejected fresh concrete and concrete trucks in concrete batching plants. The reuse of CSW as recycled aggregates or a cementitious binder for producing partition wall blocks, and the life cycle environmental impact of the blocks were assessed and compared with the conventional one designed with natural materials. The LCA results showed that the partition wall blocks prepared with fresh CSW and recycled concrete aggregates achieved higher sustainability as it consumed 59% lower energy, emitted 66% lower greenhouse gases, and produced lesser amount of other environmental impacts than that of the conventional one. When the mineral carbonation technology was further adopted for blocks curing using CO 2 , the global warming potential of the corresponding blocks production process was negligible, and hence the carbonated blocks may be considered as carbon neutral eco-product., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

• Comprehensive methodological approach was provided for identifying sustainable material sourcing regime. • Identified hotspots of existing construction material and product sourcing in Hong Kong. • Proposed alternative scenario for sustainable material sourcing based on developed decision matrix. • Alternative scenario reduced 28% of the total GHG emissions than the base scenario. While the assessment of environmental impacts of different construction materials is widely studied globally, the development of robust mechanisms for material sourcing as an integral step to transit into a sustainable supply chain is still sparse. Integrating environmental performance into an industry level supply chain is indeed a challenging task due to the absence of standardized methodology. This paper presents a methodological approach for sustainable construction material sourcing by highlighting the greenhouse gas (GHG) emissions. The proposed approach is then adopted to 12 case construction materials and products which are commonly used in to Hong Kong, and the hotspots for existing sourcing of the selected materials and products are identified while the GHG emissions are assessed based on their sourcing locations. Alternative scenarios for sourcing are identified based on a decision matrix developed according to this methodological approach. The results demonstrate that sustainable sourcing of the 12 selected materials and products by adopting the alternative scenarios can reduce 28% of the total GHG emissions compared to the base scenarios. As the scope of emission reduction for resource-scarce high-density city like Hong Kong is limited, sustainable sourcing of materials may significantly influence the emission reduction target of the construction industry. The proposed approach can help underpin sustainable sourcing of materials which can be effectively adopted in other regions to enhance the sustainability performance of the industry. [ABSTRACT FROM AUTHOR]

Highlights • Critically considered waste materials generated at different stages of building. • Influence of waste materials on building environmental impacts was comprehensively evaluated. • About 20% GHGs emission was underestimated for avoiding these in building assessment. • Adopting resource recovery principle can lead to 37% GHGs reduction from building. Abstract Buildings are responsible for a significant natural resources diminution and emissions to the environment. Thus, the building industry has become a global target for reducing environmental impacts and curbing resource depletion. Concerning the rapidly growth of buildings, life cycle assessment (LCA) is increasingly used for assessing and mitigating the associated environmental impacts from material selection to the whole building systems. However, many of the previous studies have focused on the impacts assessment from buildings within a restricted system boundary, especially lack of consideration of several critical factors when assessing the whole building, such as wastage level of raw materials during building construction and the disposal impacts, renovation and replacement of components of building and their treatment, and waste treatments during building demolition. As the industry is shifting from linear to circular, the consideration of those factors are essential for ensuring waste reduction, resources recovery and resource-efficient construction, not to mention about increasing the accuracy of such assessment. Therefore, the present study was conducted to assess the environmental impacts of the mentioned aspects at different life cycles of building by LCA. The results were then critically discussed after identifying the contribution of waste materials at different stages of building to the total impacts. The potential sustainable strategies for waste treatments during the construction, operation and end-of-life stages of building were then highlighted to help lay important foundation for adopting circular economy principle in the building industry and establishing benchmark for future reduction. [ABSTRACT FROM AUTHOR]

The construction industry will play a crucial rule in global carbon emission reduction as the embodied carbon of construction materials shares an increasing portion of a building's life-cycle carbon dioxide (CO2) emissions. In order to reduce CO2 emissions by selecting low-carbon construction materials, it is inevitable that a proper benchmarking mechanism and severity representation of different emission levels should be established, as benchmarking is a useful tool for pursuing consumer purchasing habits toward selection of low-carbon materials. In addition, high variation of carbon emissions is observed among the large number of studies and databases, and there is no consensus on how these should be used in practice. Therefore, standardization and benchmarking of emissions for construction materials are essential. In this study, a novel benchmarking approach was developed for embodied carbon emissions of commonly used construction materials by applying a fuzzy set theory. Given that a reliable local database is lacking, the benchmark was developed by referring to the existing carbon inventories, linguistic variables of severity levels from a questionnaire survey, and the fuzzy set analysis. A six-step method was proposed based on a horizontal and graphical approach. This study offers an alternative approach in benchmarking where a database or a set of real data is not available. It is expected that the developed benchmarks will help practitioners and decision-makers compare the embodied CO2 emissions of a specific batch of construction materials and select low-carbon materials in construction projects. [ABSTRACT FROM AUTHOR]

Cement is traditionally regarded as an energy and emission intensive construction material. The reduction of environmental impacts in the cement industry has gained increasing concern worldwide for environmental sustainability. As a resource-scarce city, cement production in Hong Kong is associated with high CO 2 emissions, thus contributing significantly to the high environmental impacts in the construction industry. This study herein has been conducted to comprehensively assess the energy consumption and global warming potential impacts of different types of cement manufactured in Hong Kong using life cycle assessment (LCA) techniques. Two sustainable strategies for the reduction of energy consumption and greenhouse gases emission in the cement industry were then proposed. The LCA results showed that ordinary Portland cement production has high environmental impacts mainly due to the import of associated raw materials and burning of fossil fuel. The use of alternative material, such as fly ash would help to reduce the environmental impacts. Significant impacts reductions associated with cement production can be further achieved by strategies such as the use of glass powder from locally generated waste glass bottles as part of the raw materials, and the use of a bio-fuel produced from locally generated wood wastes as a co-fuel with coal. The assessment results indicated that about 12% of the total greenhouse gases emission and 15% of energy consumption can be reduced from the cement industry in Hong Kong by using waste materials to replace virgin materials (clinker/coal). [ABSTRACT FROM AUTHOR]

In recent years, considerable efforts have been devoted to minimizing the environmental consequences from building industry globally, as the industry is notorious for its significant resource consumption and environmental emissions. However, due to a lack of data representativeness in many parts of the world, considerable variations were observed among studies, and thus makes life cycle assessment (LCA) results difficult for the decision-making purpose. In addition, the selection of low impact materials and the management of end-of-life building waste are the most important concern. By considering several strategies including data representativeness, low carbon material, and end-of-life building waste management, this study aimed to enhance the accuracy of such assessment and sustainability performance of building. An integrated LCA framework is proposed for implementing those strategies through a case specific high-rise residential building in Hong Kong. Based on case-specific/regional data, carbon emission of building was evaluated with a cradle-to-construction system boundary with the functional unit of 1 m2 of gross floor area using the IMPACT 2002+ method, and then compared to that of selecting generic databases under different scenarios. The results demonstrate that the application of case-specific and generic data would significantly influence the outcomes of the case study, as the deviations of certain magnitudes were mostly derived from different building materials that it can lead to an underestimation of carbon emissions of up to 28%. Along with using alternative materials, the adoption of the proposed materials cycling and resource recovery approach at the end-of-life building could lead to a reduction of 14% of the total emissions (i.e. excluding the use and renovation of building). The results would support data selection for accuracy of evaluation which can be used as benchmark where recognized database is not available and promote sustainability performance of buildings locally, while the proposed framework could be adopted for comprehensive evaluation globally. • Proposed integrated framework for enhancing accuracy and sustainability of building. • Data representativeness is a prerequisite for the accuracy of building LCA. • Representative data induced significantly higher carbon emission than generic data. • Using alternative materials for concrete reduced building's carbon emission. • Adopting resource recover approach in EoL significantly reduced carbon emission. [ABSTRACT FROM AUTHOR]