Construction Disposal Research Articles

System Dynamic Analysis of Impacts of Government Charges on Disposal of Construction and Demolition Waste: A Hong Kong Case Study

With the purpose of reducing the amount of construction and demolition (C&D) waste disposed to landfills, many countries and municipalities have introduced increasingly stringent C&D waste disposal charges (CDWDC) but the level of CDWDC is often determined without a clear understanding of its broad and complex impacts. Against this background, this paper aims to propose a system dynamics (SD) model that can help predict CDWDC’s environmental implications as well as its financial implications. Specifically, the proposed model explains complex causal relationships between variables such as the level of CDWDC, the amount of C&D waste disposed to landfills, the government’s revenues from CDWDC as well as the costs of supplying and operating landfills over time. For a case study, the developed model is customized and calibrated with actual data from Hong Kong, where the remaining capacities of existing landfills are limited and the need for supplying more landfills is imminent. The simulation analysis with the model predicts that the current charging levels may not be high enough to effectively control the amount of C&D waste disposed to landfills or to compensate for the costs to the government of supplying additional landfills. The analysis also predicts how much illegal dumping may increase as the level of CDWDC increases. This case study illustrates that the proposed SD model can help policy makers to see the potential impacts of increased CDWDC on the amount of C&D waste disposed to landfills, government costs and the amount of illegal dumping of C&D waste; and can therefore help them to determine the most appropriate level of CDWDC.

Optimization and influence of parameter affecting the compressive strength of geopolymer concrete containing recycled concrete aggregate: using full factorial design approach

There are several parameters that influence the properties of geopolymer concrete, which contains recycled concrete aggregate as the coarse aggregate. In the present study, the vital parameters affecting the compressive strength of geopolymer concrete containing recycled concrete aggregate are analyzedby varying four parameters with two levels using full factorial design in statistical software Minitab® 17. The objective of the present work is to gain an idea on the optimization, main parameter effects, their interactions and the predicted response of the model generated using factorial design. The parameters such as molarity of sodium hydroxide (8M and 12M), curing time (6hrs and 24 hrs), curing temperature (60°C and 90°C) and percentage of recycled concrete aggregate (0% and 100%) are considered. The results show that the curing time, molarity of sodium hydroxide and curing temperature were the orderly significant parameters and the percentage of Recycled concrete aggregate (RCA) was statistically insignificant in the production of geopolymer concrete. Thus, it may be noticeable that the RCA content had negligible effect on the compressive strength of geopolymer concrete. The expected responses from the generated model showed a satisfactory and rational agreement to the experimental data with the R2 value of 97.70%. Thus, geopolymer concrete comprising recycled concrete aggregate can solve the major social and environmental concerns such as the depletion of the naturally available aggregate sources and disposal of construction and demolition waste into the landfill.

ESTUDO DAS PROPRIEDADES DE BLOCOS SEXTAVADOS DE CONCRETO PARA PAVIMENTAÇÃO COM USO DE RESÍDUOS DE CONSTRUÇÃO CIVIL

The lack of pavement on urban roads is a problem that still affects manylocalities of the country, generating a decline in development and harmful consequences in several areas. Another problem that affects society is related to the incorrect disposal of Construction and Demolition Waste (CDW), which volume is extremely significant and the possibility of recycling (not commonly used, despite current policies that request it) is practicable, when ruled by studies and reviews that support it correctly. The objective of this study was to establish a collaborative approach to solve the two problems mentioned above by replacing the small natural aggregate with small-recycled aggregate in the concrete that composes interlocked paving. It was estimated that these would attend the current standards and correspond to the characteristics proposed, such as resistance to minimum compression of 35 MPa and maximum absorption of 6%

Engineering Behavior of Concrete with Recycled Aggregate

Concrete is extensively used as construction materials in Malaysia. Concrete contributes suitable feature for construction industry for instance durability, adequate compressive strength, fire resistance, availability and is economic as compared to other construction materials. Depletion of natural resources and disposal of construction and demolition waste remarkably claim environmental threat. In this paper, the engineering behavior, durability, and concrete microstructure of recycled concrete aggregates (RCA) on short-term concrete properties were investigated. The studied concrete at design mix proportion of 1:0.55:2.14:2.61 (weight of cement :coarse aggregates :sand :water) used to obtain medium-high compressive strength with 20%, 50%, and 100% of RCA. Results show that for the same water/cement ratio, RCA replacement up to 50% still achieved the targeted compressive strength of 25 MPa at 28 curing days. Addition, at similar RCA replacement, the highest carbonation depth value was found at 1.03 mm which could be attributed to the pozzolanic reaction, thus led to lower carbonation resistance. Scanning electron microscopy microstructure shows that the RCA surface was porous and covered with loose particles. Moreover, the interfacial transition zone was composed of numerous small pores, micro cracks, and fissures that surround the mortar matrix. On the basis of the obtained results, recommendable mineral admixtures of RCA are necessary to enhance the quality of concrete construction.

The Operational and Environmental Consequences of the Polystyrene Insulation Disposal

In connection with the significant volume of polystyrene embedded in buildings as thermal insulation, in the next few years it will be needed to solve the matter of its disposal after the end of its life cycle. Hexabromocyclododecane (HBCDD) has been used as a flame retardant in polystyrene thermal insulation (EPS and XPS) for the last 50 years. The internationally recognized Stockholm Convention on Persistent Organic Pollutants prohibits future production, use and recycling of materials that contain HBCDD. It also, to a large extent, limits the options of waste management of such materials. European legislation, in particular Regulation (EC) No 850/2004 and the so called REACH Directive, established a binding legal framework for EU Member States which reduces waste management options of material containing HCDBB practically only to incineration. In the coming years, this fact requests fundamental changes in disposal of construction and demolition waste containing the polystyrene insulation and related processes on construction sites in the Czech Republic. The research is based on the analysis of the international and the Czech legislation related to this issue, and the analysis of material and technological context. The paper focuses on possible operational, economic, energy and environmental impact on the construction industry and environment, and compares the current situation in the Czech Republic with other European countries, and assesses the readiness of the Czech Republic to deal with the upcoming legislation changes.

Development of porous ceramsite from construction and demolition waste

The disposal of construction and demolition (C&D) waste has become a serious problem in China due to the rapid increase of Chinese construction industry in recent years. In the present study, typical C&D waste was employed for ceramsite fabrication so as to find a new way for its effective recycling. A novel process was developed for manufacturing high-quality porous ceramsite according to the special chemical composition and properties of C&D waste. Most importantly, a unique bloating agent was developed for the porous structure formation since it was difficult to obtain a suitable porous structure using traditional bloating agents. The effects of processing parameters such as sintering temperature, heating rate and soaking time were investigated, and the bloating mechanism for ceramsite was discussed. The C&D waste ceramsite (CDWC), with high-intensity, low density and homogeneous mechanical properties, was much more suitable for application in the construction field. This study provides a practical process for efficient recycling of the rapidly increasing quantities of C&D waste.

Cenário do gerenciamento dos resíduos da construção e demolição (RCD) em Uberaba-MG

Em alguns municípios, os resíduos da construção civil representam 60% do montante de lixo que é gerado nos centros urbanos. A cidade de Uberaba convive com significativos impactos ambientais provocados pela não gestão dos resíduos construtivos. No município, existem áreas altamente degradadas pela destinação inadequada dos Resíduos da Construção e Demolição (RCD) ou Resíduos da Construção Civil (RCC). A falta de gerenciamento desses resíduos afeta a cidade nos aspectos econômico, sociais e principalmente ambientais. Neste trabalho, foram levantados os principais impactos ambientais que ocorreram devido à falta de gestão dos RCD na cidade de Uberaba. Foram abordados alguns pontos como: a eficiência dos "ecopontos", degradação da área da Pedreira de Léa e riscos para a saúde pública da cidade. Ainda foram discutidos os motivos que levam à não gestão dos RCD e o que tem sido feito para que futuramente esta gestão venha ser implantada. Este trabalho foi composto por revisão bibliográfica associada a visitas in loco das áreas afetadas pela destinação inadequada dos RCD. Desta forma, este trabalho propôs soluções para redução dos impactos ambientais causados pelos RCD gerenciados de maneira inadequada em Uberaba, visando obter melhorias para a saúde pública e contribuindo para a sustentabilidade ambiental da cidade.

A Recycling Review of Construction Waste in China's Road Construction Industry

Many kinds of construction wastes are now produced in China. Recycling disposal of construction wastes not only alleviate pressure on the environment but also identify certain economic and social benefits. This paper undertakes a timely review of recycling disposal of construction waste in China's Road Construction Industry. The paper presented definitions of construction wastes and described the current situation of construction wastes in China. Considering the research findings which have been achieved in the field of waste disposal, this paper discussed the approaches to recycle construction wastes in China including abandoned concrete, waste asphalt, old brick, waste timber, sewage sludge. The conclusion makes recommendations that are deemed to offer substantial benefits for both the road construction industry and society as a whole.

The effectiveness of Hong Kong's Construction Waste Disposal Charging Scheme

The Hong Kong Government introduced the Construction Waste Disposal Charging Scheme in December 2005 to ensure that disposal of construction and demolition (C&D) waste is properly priced to reduce such waste. The charging scheme is not only intended to provide an economic incentive for contractors and developers to reduce waste but also to encourage reuse and recycling of waste material thereby slowing down the depletion of limited landfill and public filling capacities. This paper examines the effectiveness of the charging scheme 1 year after implementation. A survey was conducted at Tseung Kwan O Area 137 and Tuen Mun Area 38, and daily C&D waste records were collected from landfills and public filling facilities between January 2006 and December 2006. The results of the survey show that waste has been reduced by approximately 60% in landfills, by approximately 23% in public fills, and by approximately 65% in total waste between 2005 and 2006. Suggestions for improving the scheme are provided.