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Concept: Demolition waste

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The construction industry is one of the biggest and most active sectors of the European Union (EU), consuming more raw materials and energy than any other economic activity. Furthermore, construction waste is the commonest waste produced in the EU. Current EU legislation sets out to implement construction and demolition waste (CDW) prevention and recycling measures. However it lacks tools to accelerate the development of a sector as bound by tradition as the building industry. The main objective of the present study was to determine indicators to estimate the amount of CDW generated on site both globally and by waste stream. CDW generation was estimated for six specific sectors: new residential construction, new non-residential construction, residential demolition, non-residential demolition, residential refurbishment, and non-residential refurbishment. The data needed to develop the indicators was collected through an exhaustive survey of previous international studies. The indicators determined suggest that the average composition of waste generated on site is mostly concrete and ceramic materials. Specifically for new residential and new non-residential construction the production of concrete waste in buildings with a reinforced concrete structure lies between 17.8 and 32.9 kg m(-2) and between 18.3 and 40.1 kg m(-2), respectively. For the residential and non-residential demolition sectors the production of this waste stream in buildings with a reinforced concrete structure varies from 492 to 840 kg m(-2) and from 401 to 768 kg/m(-2), respectively. For the residential and non-residential refurbishment sectors the production of concrete waste in buildings lies between 18.9 and 45.9 kg/m(-2) and between 18.9 and 191.2 kg/m(-2), respectively.

Concepts: European Union, Construction, Building, Waste, Fire protection, Occupancy, Reinforced concrete, Demolition waste

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The use of air jigging for performing multi-component separation in the treatment of mixed construction and demolition waste was studied. Sorting tests were carried out with mixtures of equal bulk volume of concrete and brick in which fixed quantities of unwanted materials - gypsum, wood and paper - were added. Experimental results have demonstrated the possibility to use air jigging to carry out both the removal of low-density contaminants and the concrete concentration in only one process step. In relation to the removal of contaminants only, the overall performance of jigging process can be comparable with that of commercial air classifiers and automatic sorting systems. Also, the initial content of contaminants seems does not have a significant effect on the separation extent. These results are of particular importance for recycling plants processing as they represent an alternative to optimize the use of air jigs. Further investigation is needed in order to evaluate the practical feasibility of such method.

Concepts: Pollution, Performance, Recycling, Separation process, Waste, Concrete, Demolition waste, Demolition

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The expressive generation of construction and demolition waste is stimulating several studies for reusing this material. The improvement of soft soils by concrete compaction piles has been widely applied for 40 years in some Brazilian cities. This technique is used to improve the bearing capacity of soft soils, allowing executing shallow foundations instead of deep foundations. The compaction piles use a high volume of material. This article explored the possibility of using recycled aggregates from construction waste to replace the natural aggregates in order to improve the bearing capacity of the soft soil, regarding its compressive strength. Construction wastes from different stages of a construction were used in order to make samples of concrete with recycled aggregates. The strength of concretes with natural aggregates was compared with the strength of concretes with recycled (fine and coarse) aggregates. Results show that all samples met the minimum compressive strength specified for compaction piles used to improve the bearing capacity of soft soils. The concrete with recycled aggregate from the structural stage had even higher resistances than the concrete with natural aggregates. This behaviour was attributed to the large amount of cementitious materials in the composition of this type of concrete. It was also observed that concrete with recycled fine aggregate has a superior resistance to concrete with recycled coarse aggregate.

Concepts: Materials science, Waste management, Compressive strength, Recycling, Construction aggregate, Waste, Concrete, Demolition waste

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An innovative strategy, based on micro X-ray fluorescence and HyperSpectralImaging in the short wave infrared range (1000-2500nm), was developed in order to characterize drill core samples collected from End-of-Life concrete. Micro X-ray fluorescence maps were realized to check the drill cores chemical composition, to develop the best approach for HSI analyses and to verify the correctness of the obtained HSI results. HSI analysis was carried out in order to recognize and classify aggregates and mortar paste in concrete. A morphological and morphometrical analysis of aggregates was also carried out on the prediction maps. Results showed as the proposed approach can be profitably applied to analyze and characterize demolition waste materials before dismantling. Starting from an efficient in-situ characterization of the objects to dismantle, demolition actions can be optimized in order to maximize the EOL concrete derived materials, minimizing the final waste.

Concepts: Scientific method, Mathematical analysis, Waste, Ice core, Core sample, Demolition waste, Construction waste, Core drill

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In Macao, about 7200 t yr(-1) of bottom ash (BA) is generated and conventionally landfilled with construction waste. Because the properties of BA are similar to those of natural aggregates, it is suitable to be recycled as construction material. However, pre-treatment processes for BA reuse may require more resource input and may generate additional environmental impacts. Life cycle assessment, multi-media transport model analysis, cost-benefit analysis and the analytical hierarchy process were conducted to evaluate the impacts of current and potential BA management scenarios regarding environmental, economic, social and regulatory aspects. The five analysed scenarios are as follows: (0) BA buried with construction and demolition waste (current system); (1) pre-treated BA used to replace 25% of the natural aggregate in asphalt concrete; (2) pre-treated BA used to replace 25% of the natural aggregate in cement concrete; (3) pre-treated BA used to replace 25% of cement in cement concrete; and (4) pre-treated BA sent to China, blended with municipal solid waste for landfill. The results reveal the following ranking of the scenarios: 3 > 2 > 0 > 1 > 4. Scenario 3 shows the best conditions for BA recycling, because the quantity of cement concrete output is the highest and this brings the greatest economic benefits. Our use of integrated analysis provides multi-aspect investigations for BA management systems, particularly in accounting for site-specific characteristics. This approach is suitable for application in other non-western regions.

Concepts: Waste management, Recycling, Construction aggregate, Fly ash, Waste, Concrete, Demolition waste, Construction waste

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Even though construction and demolition waste (CDW) is the bulkiest waste stream, its estimation and composition in specific regions still faces major difficulties. Therefore new methods are required especially when it comes to make predictions limited to small areas, such as counties. This paper proposes one such method, which makes use of data collected from real demolition works and statistical information on the geographical area under study. Based on a correlation analysis between the demolition waste estimates and indicators such as population density, buildings ageing index, buildings density and land occupation type, relationships are established that can be used to determine demolition waste outputs in a given area. The derived models are presented and explained. This methodology is independent from the specific region with which it is exemplified (the Lisbon Metropolitan Area) and can therefore be applied to any region of the world, from the country to the county level. Generation of demolition waste data at the county level is the basis of the design of a systemic model for CDW management in a region. Future developments proposed include a mixed-integer linear programming formulation of such recycling network.

Concepts: Scientific method, Demography, Population, Geography, Waste management, Waste, Region, Demolition waste

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Due to the environmental impact of construction and demolition waste (CDW), recycling is mandatory. It is also important that recycled concrete aggregates (RCA) are used in concrete to meet market demands. In the literature, the influence of RCAs on concrete has been investigated, but very limited studies have been conducted on how the origin of concrete waste and comminution processes influence RCA characteristics. This paper aims to investigate the influence of three different comminution and sizing processes (simple screening, crushing and grinding) on the composition, shape and porosity characteristics of RCA obtained from concrete block waste. Crushing and grinding implies a reduction of RCA porosity. However, due to the presence of coarse quartz rounded river pebbles in the original concrete block mixtures, the shape characteristics deteriorated. A large amount of powder (<0.15mm) without detectable anhydrous cement was also generated.

Concepts: Aluminium, Waste management, Recycling, Construction aggregate, Waste, Waste picker, Concrete, Demolition waste

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This study was carried out to develop a cost-effective and practicable sorbent for application in abrupt perfluorooctane sulphonate (PFOS) pollution accidents. The main merit of this work was that a waste material, namely construction and demolition (C&D) waste, was employed as a raw base material for the sorbent synthesis. The waste material underwent alkaline fusion-hydrothermal synthesis and a cationic surfactant cetyltrimethyl ammonium bromide (CTAB) modification process to form a CTAB-modified sorbent (CMCDSS). Experimental results showed that PFOS concentrations and solution pH had significant effect on the PFOS sorption on construction and demolition waste synthesized sorbent (CDSS) and CMCDSS (using 0.2CMCDSS as representative). PFOS could be effectively and rapidly adsorbed on CMCDSS, and sorption equilibrium was achieved within 2.5 h. The sorption amounts of PFOS on CMCDSSs enhanced along with the increase in CTAB loading amounts. Moreover, the CMCDSS can be applied effectively under acidic condition at pH 2-6 and various removal mechanisms were clarified at different sorption conditions. Accordingly, this work developed a novel and applicable material for dealing with abrupt environmental PFOS contamination accidents.

Concepts: Chemistry, PH, Pollution, Surfactant, Solution, Base, Waste, Demolition waste

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Waste management in construction is critical for the sustainable treatment of building-related construction and demolition (C&D) waste materials, and recycling of these wastes has been considered as one of the best strategies in minimization of C&D debris. However, recycling of C&D materials may not always be a feasible strategy for every waste type and therefore recycling and other waste treatment strategies should be supported by robust decision-making models. With the aim of assessing the net carbon, energy, and water footprints of C&D recycling and other waste management alternatives, a comprehensive economic input-output-based hybrid life-cycle assessment model is developed by tracing all of the economy-wide supply-chain impacts of three waste management strategies: recycling, landfilling, and incineration. Analysis results showed that only the recycling of construction materials provided positive environmental footprint savings in terms of carbon, energy, and water footprints. Incineration is a better option as a secondary strategy after recycling for water and energy footprint categories, whereas landfilling is found to be as slightly better strategy when carbon footprint is considered as the main focus of comparison. In terms of construction materials' environmental footprint, nonferrous metals are found to have a significant environmental footprint reduction potential if recycled.

Concepts: Waste management, Sustainability, Recycling, Waste, Biodegradable waste, Ecological footprint, Life cycle assessment, Demolition waste