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The importance of the building industry on environmental impacts, especially global warming potential (GWP) impact due to greenhouse gases emissions is undisputed. Thus, significant efforts have been devoted to minimize environmental impacts and waste management problems from building construction globally. Numerous studies have particularly focused on assessing the environmental impacts of buildings based on materials, construction processes and whole building systems. However, less attention has been given on some critical features, especially on temporary works (e.g., hoarding system). But the temporary works also consume considerable amounts of materials and generate significant amounts of waste due to its short service life time. Therefore, this study evaluated the environmental impacts of hoarding systems as a case study in Hong Kong with the aim to identify the areas of impacts reduction and improvements in its waste management system. A case-specific structured questionnaire survey was conducted to the relevant stakeholders to identify the essential materials, and construction, deconstruction and waste management processes of hoarding systems, whereas life cycle assessment was employed to assess the associated environmental impacts. The findings demonstrated that more than 3 tonnes of CO 2 eq GWP and 39 GJ of non-renewable energy consumption impacts were associated with 1 m of hoarding construction. This is mainly due to the use of large amounts of steel products and concrete in the construction of the hoarding system. This results and analysis can help the building industry to identify the opportunity for reducing environmental impacts, and facilitate resource-efficient and effective design of hoarding systems. [ABSTRACT FROM AUTHOR]

Abstract: Disposal of more than 300tonnes waste glass daily derived from post-consumer beverage bottles is one of the major environmental challenges for Hong Kong, and this challenge continues to escalate as limited recycling channels can be identified and the capacity of valuable landfill space is going to be saturated at an alarming rate. For this reason, in the past ten years, a major research effort has been carried out at The Hong Kong Polytechnic University to find practical ways to recycle waste glass for the production of different concrete products such as concrete blocks, self-compacting concrete and architectural mortar. Some of these specialty glass-concrete products have been successfully commercialized and are gaining wider acceptance. This paper gives an overview of the current management and recycling situation of waste glass and the experience of using recycled waste glass in concrete products in Hong Kong. [Copyright &y& Elsevier]

Prefabrication techniques have been adopted for the last two decades in public housing projects in Hong Kong, but the use of prefabrication in the private sector was encouraged only after the implementation of the Joint Practices Notes which promote its use. Although previous studies acknowledge the environmental benefits of using prefabrication, only a few studies have addressed sustainable design concepts (closed-loop) in the adoption of precast construction. A questionnaire survey was administered to experienced Hong Kong construction professionals, and case studies of recently completed building projects were compiled to ascertain the use of prefabrication with reference to life cycle approach. The findings revealed that prefabrication, combined with modular design and standard components, saved time and construction/design costs, as buildings systems were used across projects. However, in some projects, specific site conditions restricted the use of similar prefabricated building systems across projects. Surprisingly only a few participants addressed life cycle design concepts such as design for deconstruction when adopting precast construction. Also, although it is common knowledge that flexible and demountable prefabricated building systems would result in efficient use of resources, their use is seldom practised in Hong Kong. [ABSTRACT FROM AUTHOR]

This research resorted to the use of construction operations simulation modeling to investigate the cost efficiency of waste-handling practices on the Kai Tak Airport demolition project in Hong Kong. By modeling the site operation of sieving and stockpiling broken concrete, the well-established construction simulation methodology of CYCLONE was contrasted with the newly developed simplified discrete event simulation approach (SDESA). Further, the SDESA model was readily extended to include (1) raw demolition waste collecting and sorting; (2) broken concrete sieving and stockpiling; (3) steel bar recycling; and (4) debris disposal at the landfill. The production rate derived from simulation was indicative of a close match between the simulation model and the actual site system. The resulting simulation model provided a basis for evaluating the cost efficiency of actual site operations and alternative resource provision scenarios being postulated. Through computer simulation, the actual site operation was found smooth and efficient with utilization rates for resources of different types ranging from 79 to 99%. In addition, the cost–time reduction ratios were calculated for four alternatives of resource provisions in comparison with the original base case. The research findings suggested that provided the project budget had satisfied the higher cash flow requirement, doubling the resource provision on site would potentially cut the project duration by half and not increase the total direct cost. [ABSTRACT FROM AUTHOR]

Abstract: In 2004, over 20 million tonnes of construction and demolition (C&D) wastes were generated in Hong Kong. Since the local landfills will be saturated in about 8 years, it is important to find a viable way to reuse these waste materials as to alleviate the demand on public fill capacity. In order to tackle the problem, the Hong Kong government has set up a temporary recycling facility in Hong Kong in 2002 for producing different sizes of recycled aggregate for use in various construction materials. This paper summarizes the details of the construction of the Hong Kong Wetland Park which consumed approximately 14,300m3 of concrete prepared with recycled aggregate. However, as of today, the recycled aggregate being reused is stringently restricted to recycled concrete aggregate (RCA). The use of other wastes such as brick and ceramic tile aggregate is prohibited momentarily even the combination of bricks and ceramic tiles constitutes a large portion of the C&D wastes. In order to facilitate the wider use of the inert portion of the C&D wastes, a preliminary study was conducted to investigate the possibility of using crushed brick and tile aggregate derived from construction and demolition waste stream as a replacement of fine aggregate in concrete. The effects of the use of fine crushed brick and tile aggregate as a 20wt.% replacement of natural sand on the fresh and mechanical properties are presented. [Copyright &y& Elsevier]

Solid waste disposal facilities have become scarce in both developed democratic and lower-income socialist states such as the mainland China. The cases of Guangzhou, Jiangmen and Dongguan are analysed to elucidate the factors for siting difficulties and the unique siting style in China. A number of factors are contributing to siting difficulties in Southern China. Irrational applications of the self-sufficient principle at local waste management, poor environmental track records of previous and existing disposal facilities have all severely restricted the supply of waste disposal sites. In addition, rapid increase in waste generation and the use of old-fashioned equipment in waste facilities are speeding up the consumption of landfill space. While the top-down approach is still the norm in waste facility siting, local governments and host communities in China can effectively block the establishment of waste facility as a result of increasing decentralisation of decision making power where even grass root level governments are granted more autonomy in decision making. [ABSTRACT FROM AUTHOR]

Aims to identify the minimum size of the external costs involved with landfilling and incineration in Hong Kong. Disposal cost and charges; Waste collection concerns; Energy recovered from landfill gas; Local and global pollution from waste transport.

Analyzes the results of two surveys conducted in 1992-1993 regarding the attitudinal differences in source separation and waste reduction between the general public and the housewives in Hong Kong. Avoidable waste; Waste collection charges; Green premium; Source separation of household waste; Beverage containers and cell batteries.

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. [ABSTRACT FROM AUTHOR]

Abstract Prefabrication is considered an important solution to tackle the issues of construction waste generation, and the high-risk and labour-intensive activities associated with conventional construction methods. This study assesses the key hindrances of adopting prefabrication and provides recommendations for promoting prefabrication in Hong Kong. Twenty-two hindrances were identified in the literature and classified in six groups. A questionnaire survey and face-to-face interviews were conducted to examine the level of importance of the barriers, and to provide comprehensive analyses of each hindrance. The most significant hindrances were "Inflexible for design change", "Lack storage space on site", "Long lead-in time", "Long design time", "High initial cost" and "High total cost". Based on the findings of the survey and interviews, six recommendations were proposed to promote the usage of prefabrication in Hong Kong such as "Just-In-Time management", "BIM technology", "Legislation for refabrication", "Potential government measures", "Encouragement of design and building procure" and "Increase the consumer's confidence". Highlights • Lack storage space on site is a major hindrance to using prefabrication in dense cities. • Inflexible for late design change is a major hindrance to using prefabrication. • Just-in-time delivery & BIM optimize prefabricated building process in dense cities. • Implementation of legislation for prefabrication can promote its use. • Adoption of design and build procurement method can promote prefabrication use. [ABSTRACT FROM AUTHOR]

[Display omitted] • EIPP is a green and high-performance S/S method for heavy metal tailings treatment. • The treated tailings reach strength of 2.7 MPa with low pollution risk. • S/S efficiency is determined by tailings density and mass of reactant and enzyme. • Formed Pb 9 (PO 4) 6 and newberyite lead to Pb immobilization and strength improvement. The accumulation of heavy metal tailings has caused serious environmental and geological concerns. Therefore, treatment and recycling of heavy metal tailings have become urgent and vital. To this end, this paper proposes a biological solidification and stabilization (S/S) method, which applies enzymatically induced phosphate precipitation (EIPP) to strengthen Pb-Zn tailings and reduce the hazard of the heavy metals. The effectiveness and mechanism of EIPP-S/S have been systematically explored, including the effect of enzyme and reactant concentration, and tailings density on the treatment efficiency. The results showed that MgHPO 4 (H 2 O) 3 (newberyite) and Pb 9 (PO 4) 6 were the main products of EIPP. The newberyite strengthened the tailings through connecting tailing particles and filling the pores, and the solidification effect was positively related to the reactant content and tailing compactness. The strength of the treated tailing sample could reach 2.7 MPa at a relative density of 90% with a reactant concentration of 1.5 M. After treatment, about 40% of Pb in the tailings changed from an acid-soluble state to oxidation state and residual state, as a result of the precipitation of Pb 9 (PO 4) 6. The concentration of leached Pb from the treated tailings under an acid rain environment was reduced from 0.86 mg/L before treatment to less than 0.02 mg/L, well below the limit of 0.1 mg/L in China's ground/surface water. This study provides new insights into the treatment and reuse of tailings by applying an innovative EIPP-S/S method, which can flexibly treat tailings in an environmentally friendly manner. [ABSTRACT FROM AUTHOR]

Barium slag (BS) is a hazardous industrial solid waste formed during the production of barium carbonate. The accumulated stock of BS in China has exceeded 10 million tons, which urgently needs to be recycled in an efficient and sustainable way. BS contains a lot of soluble Ba2+ with a leaching concentration up to 2000 mg/L in water. Meanwhile, Ba2+ is an alkali-earth metal which can activate ground granulated blast furnace slag (GGBFS). This paper explores the possibility of incorporation BS as an admixture for alkali activated slag (AAS) cement. The mechanical property and microstructure evolution of AAS pastes with addition of BS are investigated in comparison with pure AAS paste. The results indicate that the addition of BS could significantly enhance mechanical strength of AAS paste, attributing to the increased hydration degree and the formation of dense pore structure. In addition, the leaching concentration of Na+ shows a significant decline by incorporation of BS in AAS paste, associated with the changed composition of hydration products. Therefore, BS is a promising admixture for AAS cement and holds great potential for promotion and application. [Display omitted] • The addition of BS significantly improves mechanical strength of AAS paste. • The composition of main hydration products is changed by incorporation of BS. • The incorporation of BS promotes more Al to substitute Si into C-A-S-H gel. • The BS added AAS paste has more harmless gel-pore and less harmful macropore. • The BS leads to a decline in leaching concentration of Na+ in AAS paste. [ABSTRACT FROM AUTHOR]