Assessment of construction and demolition waste leachate using column percolation test: effect of paint presence

A study on the spatial network characteristics and effects of CDW generation in China.

The Zambian Construction Industry (ZCI) is one of the fastest growing sectors in Zambia arising from increased infrastructure development. The ZCI, like elsewhere, is composed of many players including designers, contractors, regulators, manufacturers and suppliers of construction materials. The country has seen an upsurge in Construction and Demolition Waste (CDW) generation due to increased construction activities. However, opportunities for utilizing CDW for sustainable construction and management have been minimal. Most research in developing countries has focused on Municipal Waste Management (MWM) rather CDW. In Zambia, CDW is a challenge in the absence of legislation, guidelines and regulation. In the developed countries, guidelines, legislation and regulation, exist. Sustainable utilization of CDW in Zambia is limited due to inadequate policy guidelines and legislation. The research aimed at estimating the levels of CDW waste generation and utilization, and proposing a framework for sustainable utilization and management of CDW. The research required both qualitative and quantitative data. Primary data was collected through questionnaires, interviews and site visits whilst secondary data was obtained through literature review. The research, conducted in four provinces of Zambia, established that CDW generation rates were mainly in the 1-10% levels and utilization was low, regardless of the type of project. The main cause for such generation levels was poor skills and workmanship. Further, there are no specific policies dealing with CDW in Zambia. A frame work for estimating and quantifying CDW generation over the whole life cycle of a construction project is also proposed.

In Bangladesh, the minimisation of construction and demolition waste (CDW) generation is a demanding need to alleviate the environmental burden. Various barriers limit the effective CDW management strategies in this economy. Hence, this paper aims to explore the major obstacles to managing construction and demolition waste in Bangladesh. Major barriers identified in previous studies were selected through a literature review, and a tentative question list was prepared. Afterwards, by the suggestion of four experts, a structured questionnaire was designed to collect the respondents' knowledge on CDW, impacts of CDW and 19 barriers that hinder the effective implementation of CDW management. On-site visits and face-to-face interviews were to collect research data. The results of the questionnaire survey were analysed using ranking analysis. The findings show that waste generation in construction and demolition sites is different. Primary wastes generated in demolition sites are concrete and bricks, whereas in construction sites, the percentage of concrete, timber, brick, metal, sand, etc., is high. This study also evaluated that female respondent, mainly field workers, have more knowledge about CDW management than males. However, the number of female workers is few due to socio-cultural barriers. Based on the ranking analysis, the four most significant barriers that were identified hindering the effective CDW management are: 'Negligence and carefree attitude of workers', 'Poor supervision', 'Inadequate workers' skill', 'Space lacking for on-site storage'. The current study contributes to the field by identifying and highlighting the challenges to CDW management implementation in Bangladesh and providing remedial solutions to the identified barriers. Furthermore, the results could be helpful to provide information for developing strategies to improve CDW management strategies in Bangladesh.

Construction and demolition waste management in China through the 3R principle

Reasonable evaluating the economic benefits and social welfare of construction and demolition waste (CDW) recycling contributes to CDW investments and decision-making. The formation mechanism of comprehensive benefits on CDW recycling is analyzed by applying the pressure-state-response framework from the resource economics, and the article constructed the evaluation model of comprehensive benefits on CDW recycling. The context of CDW management, supply and demand of recycled products, and the input-output effectiveness of CDW management are determined and discussed in the case of Chongqing. These findings suggest that 1) the CDW recycling rate changed between 0.06 and 0.14, which indicated that construction and demolition waste are mostly in landfill; 2) the supply-demand ratio of CDW recycled products fluctuates between 0.1 and 0.25, which suggests that the supply-demand of recycled products is a serious mismatch, and then this mismatch is the pressure and driving force of CDW recycling development; 3) the benefit-cost ratio of CDW management varies between 0.16 and 0.35, which suggests that the input-output of CDW management is a significant disproportion, and the disproportion not only conforms to the economic man of the investor who do not participate in CDW recycling,but also reflects the stakeholders’ response to CDW management. Based on the previous study, the suggestion is discussed and studied on the CDW supply-demand side applying supply-demand ratio and benefit-cost ratio.

Improve the quality of construction and demolition waste by separation techniques

Potential evaluation of the use of construction and demolition waste (CDW) in the recovery of degraded soils by mining in Brazil

Nowadays, the construction, remodelling and demolition operations can cause serious environment impacts. These activities produce materials defined as construction and demolition wastes (CDW). The CDW generated in Europe represents around 25–30 % of total waste. In EU 28 CDW production is about 821,160,000 t, but there is a significant difference among the European countries, mainly because of the variation of construction and demolition activity. In 2011, the total production of CDW in Portugal was around 930,000 t, but regional production is not homogeneous. The substantial inert fraction from the CDW makes them suitable for reuse. The present study aims to quantify and characterize CDW from residential recuperation of small constructions in Portugal and then propose mitigating measures to improve CDW management. The results obtained by bibliographic research revealed that the construction and demolition activity has decreased significantly in the last years and consequently CDW production. In addition, it was observed a big number of entities were involved in CDW management. Therefore, it was necessary to select a specific area from Portugal (Setubal region) which has thirteen City Halls. The surveys had scarce response. This can be explained by the lack of obligation of enterprises with less than ten employees to register CDW production and because in some regions the CDW are mixed with municipal solid waste. Most of the CDW collected from Setubal region was disposed in landfill. In order to reduce CDW production it is necessary to promote and make available recycled materials for small works at low cost.

Enhancing sorting efficiency in cluttered construction and demolition waste streams via boundary-guided grasp detection.

This study conducted a review of a wide array of documents related to construction and demolition waste (CDW) management in Southeast Asia (SEA). CDW definitions, current state of CDW generation and composition, CDW flow and institutional arrangements for CDW management were assessed. CDW generation was estimated in SEA countries where data are unavailable. The review results indicated the inadequacy of existing CDW management in almost all SEA nations, with a dearth of proper data on the amount of CDW generated and proportions of CDW components. Insufficient legal documents designed for CDW and unclear assignment of prime responsibilities for CDW management have also been observed. The SEA’s high ratio of CDW generation to the construction industry’s value added implies a great waste burden that construction activities there are causing compared to their contribution to the regional economy. This study suggested a need for more holistic and aggressive methods of sustainable CDW management, namely: developing legalised systematic approaches to CDW data collection and database establishment; enabling public private partnership models, which involve the private sector in establishing recycling facilities and internalise informal actors in formal CDW management arrangement; applying recycling-favourable policies such as green public procurement, along with disposal fee schemes.

The lack of appropriate management of construction and demolition waste (CDW) is being increasingly associated with ecosystem damage and environmental impacts in the proximity of open dumping areas. Yet, the development and optimization of management models require accurate prediction of generation rates and waste composition, often lacking in developing countries. As such, this study aims at spatially quantifying CDW and analyzing its dynamics in Lebanon. The study developed a model for CDW classified quantification in the six governorates of Lebanon. The outcome can be used as the main input for modeling management strategies and designing processing facilities for CDW at the national and/or governorate scales. The construction waste and demolition waste were assessed separately. Daily construction waste generation ranges between 717 and 6353 in the Bekaa and Mount Lebanon governorates, respectively. The annual growth rate varied between 5.6 and 13%, with an average of 10–11% in most of the country. As to demolition waste, a total of 810 tons is generated daily in Lebanon.

Quantification of construction and demolition waste (CDW) is vital for building up an effective waste management system as it helps in developing practical approaches, establishing waste collection centres, arranging labour and transport facilities. The present work focuses on the estimation of CDW generated during the time of demolition, construction, renovation of small-scale residential structures and identifying the disposal site for dumping of CDW. Data regarding total CDW disposed at the dumpsite and information related to the challenges faced by demolition contractors were collected. Based on the collected data, correlation analysis, regression analysis, forecasting and energy calculations were performed. The total CDW generated at the generation sites, dumpsites and their Waste Generation Index (WGI) was calculated. About 84% of CDW was contributed by demolition works with WGI of 57.55 kg/m2, where brick masonry and concrete are the major contributors of CDW with 31% and 21%, respectively. There was not much variation between the observed and predicted CDW generation in case of construction works, but small variation was witnessed in demolition works which was negligible. On forecasting the CDW to be collected at a dumpsite (Rampura), it was estimated to collect about 51,680 tonnes for a year. The maximum energy consumption in transporting CDW from site to dump yard was contributed by dump trucks compared to tractors. The average distance between the CDW generation site and the disposal dumpsite per trip was about 21 km.KeywordsConstruction and demolition wasteDumpingEstimationWaste generation indexForecasting

Railway engineering generates large amounts of construction and demolition waste (CDW). To quantify the amount of CDW generated from railway engineering projects throughout the whole life cycle, a process-based life cycle assessment model is proposed in this paper. The life-cycle CDW is divided into four parts: CDW from off-site transportation of construction materials (OSTCM), CDW from site operation wastage of construction materials (SOWCM), discard ballast from roadbeds, stationyard, bridges and tunnels (DB), and CDW from reparation and renewal of aging components (RRAC). Yun-Gui Railway is selected as a case study to validate the developed model, and an uncertainty analysis is conducted with Oracle Crystal Ball software. The results show that between 175 and 311 million tons of CDW is generated throughout the whole life cycle of Yun-Gui Railway. DB is the largest component of the life-cycle CDW from railway engineering projects. This indicates the negative environmental impacts of railway construction can be significantly mitigated by optimizing the location of ballast disposal sites and developing suitable landfill proposals. Also, the CDW generated by wastage of construction materials during off-site construction and site operation is important in waste management in railway engineering projects, in which rubble, sand, and cement have the high potential for waste reduction. Findings from this study can contribute to the knowledge body as well as the engineering practice in green railways.

As urbanization spreads rapidly, more structures are being built, and more construction and demolition waste (CDW) is produced, occupying about 36–40% of the total solid waste generation in the world; hence, CDW has become a burden nowadays. Moreover, the construction of low-rise buildings on weak soil is always challenging and costly due to the soil's high compressibility and low bearing capacity. Sand or other granular materials are commonly used to improve the compressibility behavior and associated settlement, drainage, and shear strength of weak soil. The massive use of natural sand for construction purposes of different civil engineering structures have lessened their reserves in recent times, increasing their price and destroying the balance in the environment. Among the several methods of improving soil, this research uses fine-grained CDW to improve the geotechnical behavior of weak soil under study. The main objective of this research is to observe the changes in soil properties after mixing with CDW. Recycled waste mortar powder has been selected as CDW mixed in different percentages in the soil. In addition, CDW powder was inserted into soil mass as a circular powder column in triangular and square grid patterns as an alternative to the sand column. CDW in the soil samples improved consolidation settlement, and reduced settlement time and compression index. Increments in the pre-consolidation pressure, consolidation rate, and permeability of the clay-CDW mixtures were also remarkable. Soil improvement through reusing CDW is a sustainable way to solve problems in solid waste management and the soft soil settlement issue under a shallow foundation, ultimately reducing the environmental footprints, saving natural resources, and supporting the circular economy concept.

Evaluation of carbon and economic benefits of producing recycled aggregates from construction and demolition waste