•A closed-loop LCA on RAC utilization in China with entire local LCI is performed.•Comparative results on environmental impact between NAC and RAC is achieved.•Possible opportunity for lowering ...environmental impact of RAC is proposed.
This paper studies the potential environmental impact of recycled coarse aggregate (RCA) for concrete production in China. According to the cradle-to-cradle theory, a closed-loop life cycle assessment (LCA) on recycled aggregate concrete (RAC) utilization in China with entire local life cycle inventory (LCI) is performed, regarding the environmental influence of cement content, aggregate production, transportation and waste landfilling. Special attention is paid on the primary resource and energy conservation, as well as climate protection induced by RAC applications. Environmental impact between natural aggregate concrete (NAC) and RAC are also compared. It is shown that cement proportion and transportation are the top two contributors for carbon dioxide (CO2) emissions and energy consumption for both NAC and RAC. Sensitivity analysis also proves that long delivery distances for natural coarse aggregate (NCA) leave a possible opportunity for lowering environmental impact of RAC in China.
•This paper develops a system dynamics model of construction waste reduction management at the construction phase.•Source reduction is an effective management measure in reducing 27.05% of total ...waste generation.•Construction waste reduction implementation can reduce 53.77% of landfill.•Illegal dumping problem is serious and it is necessary to strengthen government legislations.
A huge amount of construction waste has been generated from increasingly higher number of construction activities than in the past, which has significant negative impacts on the environment if they are not properly managed. Therefore, effective construction waste management is of primary importance for future sustainable development. Based on the theory of planned behaviors, this paper develops a system dynamic model of construction waste reduction management at the construction phase to simulate the environmental benefits of construction waste reduction management. The application of the proposed model is shown using a case study in Shenzhen, China. Vensim is applied to simulate and analyze the model. The simulation results indicate that source reduction is an effective waste reduction measure which can reduce 27.05% of the total waste generation. Sorting behaviors are a premise for improving the construction waste recycling and reuse rates which account for 15.49% of the total waste generated. The environmental benefits of source reduction outweigh those of sorting behaviors. Therefore, to achieve better environmental performance of the construction waste reduction management, attention should be paid to source reduction such as low waste technologies and on-site management performance. In the meantime, sorting behaviors encouragement such as improving stakeholders’ waste awareness, refining regulations, strengthening government supervision and controlling illegal dumping should be emphasized.
•The paper reviews the production and utilisation of recycled aggregate in concrete.•Critically analysed the globally published data on recycled aggregate standards.•This review may help to alleviate ...the concerns of consumers.•This paper can encourage and further promote the use of recycled aggregate.
Solid waste has been an inevitable by-product of the operations of industrialised societies. One result of economic growth is an increase in generation of solid waste which normally was dumped in landfills and caused contamination of soil, water and air from toxic substances such as polychlorinated bi-phenyls (PCB’s), asbestos, construction chemicals, heavy metals, but the scarcity of land-filling areas, industrial growth as well as strict environmental regulations in developed and developing economies has led to the global re-assessment of the methods employed to recycle and utilise construction and demolition (C&D) waste as recycled aggregate for civil engineering projects i.e. construction and infrastructure development. Depending on their quality, recycled aggregate produced from C&D waste can be employed in various civil engineering works, which can help in a long way the economic and environmental sustainability of respective countries. With further research and development into overcoming technical as well as market barriers, considerable increase in recovery rates can be achieved with the existing technologies in developed economies. The main aim of this study is to review the literature on the production and utilisation of recycled aggregate in concrete, concrete pavements, roadway construction, and other civil engineering works and some discussion on the savings on CO2 emissions have been included. The globally published data on recycled aggregate standards (normative documents) of various countries have been systematically analysed and evaluated, and some barriers mentioned. This review may help to alleviate the concerns of consumers and encourage and further promote the use of recycled aggregate on a larger scale in civil engineering projects.
Solid waste arisen from construction activities is grave concern in many economies. Given its negative impacts to the natural environment as a public good, construction waste is often heavily ...regulated by authorities. Hong Kong is no exception to this; over the past decades, a series of construction waste management (CWM) policies including regulations, codes, and initiatives have been introduced by the Government and her executive arms. It comes to an opportune time to retrospectively examine the effectiveness of these policies with a view to providing insights for further improvement. The aim of this paper is thus to examine CWM policies and their effectiveness in Hong Kong by conducting a longitudinal study. The evaluation of the policy effectiveness is derived by triangulating empirical data collected from various sources including Hong Kong Census and Statistics Department, Civil Engineering and Development Department, Environment Protection Department, and Hong Kong Construction Association with the qualitative data gleaned from interviews and case studies in construction sites, waste sorting facilities, and landfills. It is found that Hong Kong is actively trying new CWM policies based on latest waste management philosophies available (e.g. reduce, reuse, and recycle principle, and polluter pays principle). These policies have formed an interlocking, and relatively effective policy framework for CWM in Hong Kong. However, new initiatives are desired if aiming to change the gloomy situation since 2006 when the construction waste disposal charging scheme was effectively implemented. This research provides insightful understanding of CWM policies and their effectiveness, which is often concerned policies makers, researchers, and the like.
•Growing cities are facing environmental and safety risks of construction debris.•Mismanagement has led to serious impacts, such as the Shenzhen and Chennai disasters.•Dumping dominated the disposal, ...and consumed considerable scarce scare land resources.•More research on construction debris reduction is essential.•Rethinking of urban planning to avoid large scale urban renewal is urgently needed.
How can growing cities be expanded in a sustainable way? Huge waste generation has become a major challenge in many growing cities, particularly in developing countries. China’s annual C&D waste generation was and estimated 2.4 billion tonnes in the past decade, which is 15 times more than municipal solid waste generation. India has less C&D waste generation than China, yet still is as high as 530 million tons in 2013. However, only around 5% of C&D waste was reused in these countries and the rest largely ends up in dumping sites for disposal. As China and other developing countries continue to urbanize in the next decades, C&D waste management will continue to be a significant challenge for urban sustainability in terms of the environment, economics, and safety. We therefore critically reviewed the C&D waste generation, management, and challenges faced by the fast expanding cities in China and other developing countries. We also compared the current characteristics of key C&D waste systems in developing and developed countries. Recommendations for swift action are made for policy makers in growing cities.
A large amount of construction waste is generated every year over the world. Many studies indicated that waste management fee is an effective approach that could minimize the generation of waste and ...maximize the diversion rate of landfills. However, there are limited number of studies conducted on determining the waste management fee for construction waste. This study proposes a method to optimize the construction waste management fee by considering life-cycle environmental impacts of construction waste and society's willingness to improving the management of construction waste. This contributes to the knowledge body of construction waste management by expand the current models from these aspects. The environmental impacts taxes are selected as the evaluation basis that avoided subjective consequences in previous models. This study provides a series of suggestions for construction waste management sector in China to determining construction waste management fee, based on the findings. It is suggested that the waste management fee for 1 ton of metal waste could be 60.42 yuan (about US$9.30), followed by wood waste 38.47 yuan (about US$5.92) and masonry waste 27.65 yuan (about US$4.25). The average waste management fee for unit comprehensive construction waste of all types of buildings could be 23.61 yuan/ton (about US$3.63/ton). The average waste management fee for unit construction area (1 m2) of all types of buildings is 0.81 yuan/m2 (about US$0.12 m2). The proposed method and suggestions could be helpful for waste policy makers as well as researchers for developing construction waste management fee schemes. It worth to mention that these proposed waste management fee would vary over time and regions, as any change of factors in the calculation models would result in a change of the final result. As the application of waste management fee would affect the attitudes and behaviors of stakeholders including the government departments, owners of landfills, collection and transportation parties, waste recycling parties, landfills parties and so on. The determination of waste management fee is a very complex issue and need to be solved via systematic approaches from different perspectives.
The world has witnessed unparalleled economic development over the past decades, but accompanied by large amount of carbon emissions, which triggered the global warming. It is critical for the global ...sustainable development by decoupling economic growth from carbon emissions at country level, specifically for the largest emitter, China. This study conducts a decoupling analysis from the perspective of carbon intensity (CI), per capita carbon emissions (PC) and total carbon emissions (TC) with reference to 30 Chinese provinces, covering the period of 2001–2015. Based on the Log Mean Divisa Index (LMDI) method, the effects of energy structure (ES), energy intensity (EI), economic output (EO) and population size (P) on TC at provincial level are investigated. Results show that: (1) a strong decoupling relation between GDP and CI is found in most provinces except Hainan, Qinghai and Xinjiang, while there is large room for China to decouple completely from PC and TC; (2) EO and EI are the dominated inhibiting and promoting factors respectively for carbon emission reduction; (3) ES effect on increasing carbon emission changes between positive and negative, while P has a positive but insignificant effect on the increase of carbon emissions for most provinces. The results help local governments formulate measures to coordinate regional economic development and carbon emission reduction.
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•Decoupling degree of three carbon indexes in 30 Chinese provinces is analyzed.•China has made great strides in decoupling economic growth from carbon emissions.•Improving energy efficiency is the most effective way to control carbon emission.•The understanding of impact factors offers references for emission mitigation.
Construction and demolition waste (C&DW) as a direct consequence of rapid urbanization is increasing around the world. C&DW generation has been identified as one of the major issues in the ...construction industry due to its direct impacts on the environment as well as the efficiency of construction industry. It is estimated that an overall of 35% of C&DW is landfilled globally, therefore, effective C&DW management is crucial in order to minimize detrimental impacts of C&DW for the environment. As the industry cannot continue to practice if the resources on which it depends are depleted, C&DW management needs to be implemented in an effective way. Despite considering many well-developed strategies for C&DW management, the outputs of the implementation of these strategies is far from optimum. The main reason of this inefficiency is due to inadequate understanding of principal factors, which play a vital role in C&DW management. Therefore, the aim of this research is to critically scrutinize the concept of C&DW and its managerial issues in a systematic way to come up with the effective C&DW management. In order to achieve this aim, and based on a systematic review of 97 research papers relevant to effective C&DW management, this research considers two main categories as fundamental factors affecting C&DW management namely, C&DW management hierarchy including reduce, reuse, and recycle strategies, and effective C&DW management contributing factors, including C&DW management from sustainability perspective, C&DW stakeholders’ attitudes, C&DW project life cycle, and C&DW management tools. Subsequently, these factors are discussed in detail and findings are scrutinized in order to clarify current and future practices of C&DW management from both academic and practical perspectives.
•Mechanical properties of geopolymer composite with recycled aggregate were investigated.•Effects of GGBFS incorporation and recycled aggregate replacement were investigated.•Improvements in ...physical-mechanical properties were achieved with GGBFS inclusion.•Recycled aggregate adversely affected the mechanical properties of geopolymer composites.•Relationships between the compressive strength and other mechanical properties are proposed.
The properties of fly ash and ground granulated blast furnace slag (GGBFS) combination based geopolymer composites containing recycled aggregate are investigated in this study, which obtained from construction and demolition wastes. The effects of recycled aggregate replacement and GGBFS inclusion on the physical and mechanical properties of geopolymer composites were investigated in this study. The scanning electron microscopic (SEM) were conducted to provide a thorough insight into the characterization of microstructures. The results reveal that using recycled aggregate has an insignificant impact on workability and setting time, while it causes a reduction in physical and mechanical properties. The inclusion of GGBFS reduces workability and setting time. However, improved physical and mechanical properties can be achieved in the geopolymer composites after the incorporation of GGBFS, and this effect is more prominent in the geopolymer composites containing recycled aggregates. The water absorption and sorptivity exhibit a strong correlation with the volume of permeable voids of geopolymer composites. Besides, very good relationships were established between the compressive strength and other mechanical properties, and these relationships fitted reasonably well with the other predictions.
As more than 50% construction and demolition (C&D) wastes are composed of concrete debris in Hong Kong, recycling this debris into Recycled Aggregate (RA) for production of Recycled Aggregate ...Concrete (RAC) is an efficient way to alleviate the burden on landfill areas. Since RA is generated from concrete debris which has undergone years of services, the resulting RAC bears the weaknesses of lower density, higher water absorption, and higher porosity that limit them to lower-grade applications. Pinpointing to these weaknesses, Tam et al. 2005, Cement Concrete Res 35(6):1195-1203 developed the Two-Stage Mixing Approach (TSMA) for improving the strength of RAC, leading to the possibility in applying RAC for higher-grade applications. While the improvement in strength by TSMA has been proven in Tam et al.'s work 2005, Cement Concrete Res 35(6):1195-1203, the durability, in terms of deformation (shrinkage and creep) and permeability (water, air and chloride permeability), remains to be verified. In this paper, 0%, 20% and 100% of RA substitutions have been experimented to compare the durability performance of the Normal Mixing Approach (NMA) and the TSMA. Experiment results highlight that: (i) the higher the substitutions of RA, the weaker the performance of RAC; and (ii) the deformation and permeability of RAC can be enhanced when adopting TSMA. Therefore, it demonstrates that TSMA can help to improve the durability of RAC, on top of the previously verified strength improvement, and thus opening up wider applications of RAC.
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