Recycling construction and demolition wastes – a UK perspective

Removal of atmospheric CO2 by engineered soils in infrastructure projects

The use of crushed basic igneous rock and crushed concrete for enhanced rock weathering and to facilitate pedogenic carbonate precipitation provides a promising method of carbon sequestration. However, many of the controls on precipitation and subsequent effects on soil properties remain poorly understood. In this study, engineered soil plots, with different ratios of concrete or dolerite combined with sand, have been used to investigate relationships between sequestered inorganic carbon and geotechnical properties, over a two-year period. Cone penetration tests with porewater pressure measurements (CPTu) were conducted to determine changes in tip resistance and pore pressure. C and O isotope analysis was carried out to confirm the pedogenic origin of carbonate minerals. TIC analysis shows greater precipitation of pedogenic carbonate in plots containing concrete than those with dolerite, with the highest sequestration values of plots containing each material being equivalent to 33.7 t C ha^-1 yr^-1 and 17.5 t C ha^-1 yr^-1, respectively, calculated from extrapolation of results derived from the TIC analysis. TIC content showed reduction or remained unchanged for the top 0.1 m of soil; at a depth of 0.2 m however, for dolerite plots, a pattern of seasonal accumulation and loss of TIC emerged. CPTu tip resistance measurements showed that the presence of carbonates had no observable effect on penetration resistance, and in the case of porewater pressure measurements, carbonate precipitation does not change the permeability of the substrate, and so does not affect drainage. The results of this study indicate that both the addition of dolerite and concrete serve to enhance CO₂ removal in soils, that soil temperature appears to be a control on TIC precipitation, and that mineral carbonation in constructed soils does not lead to reduced drainage or an increased risk of flooding.

An overview of the waste hierarchy framework for analyzing the circularity in construction and demolition waste management in Europe

The construction sector is the biggest driver of resource consumption and waste generation in Europe. The European Union (EU) is making efforts to move from its traditional linear resource and waste management system in the construction sector to a level of high circularity. Based on the theory of circular economy, a new paradigm called waste hierarchy was introduced in the EU Waste Framework Directive. This work uses the framework of the waste hierarchy to analyze the practice of construction and demolition waste (CDW) management in Europe. We explore the evolution of the waste hierarchy in Europe and how it compares with the circular economy. Then, based on the framework, we analyze the performance of CDW management in each EU member state. Innovative treatment methods of CDW, focusing on waste concrete, is investigated. This brings insight into optimizing and upgrading the CDW management in light of advanced technologies and steering the pathway for transitioning the EU towards a circular society.

Circular Economy and Virtual Reality in Advanced BIM-Based Prefabricated Construction

This paper presents a new virtual reality (VR)-based approach to advanced learnings and experiences of the circular economy (CE) in the construction industry. The approach involves incorporating game design and a building information modelling (BIM) digital twin of a purposed CE prototype building. Our novel approach introduces VR environments designed to provide a visual representation of materials and components that can be reintroduced into the supply chain at the end of life and their removal procedures and material provenance. A case study methodology was applied to a purposely designed CE building, namely the Legacy Living Lab (L3). To reflect the real-life building, L3’s BIM model was combined with Unify game software to advance the literature in three key areas. First, the research investigates VR tools that will allow building designers to view and implement their strategies to advance CE design. Second, this research proposes an advanced VR tool to visualise the bill of quantities (BoQ) and material stock embedded in the studied building, further understanding concepts such as buildings as material banks. Finally, the proposed VR environment defines CE techniques implemented within the case study to be disseminated across the vast construction industry. This VR research identifies three key pillars in reducing the waste generated by the construction industry: education, documentation and visualisation. Furthermore, this paper provides a visual link between the BIM, BoQ and resiliency of the selected materials.

Strategies for a Circular Economy in the Construction and Demolition Sector: Identifying the Factors Affecting the Recommendation of Recycled Concrete

With increasing urbanisation, new approaches such as the Circular Economy (CE) are needed to reduce resource consumption. In Switzerland, Construction & Demolition (C&D) waste accounts for the largest portion of waste (84%). Beyond limiting the depletion of primary resources, implementing recycling strategies for C&D waste (such as using recycled aggregates to produce recycled concrete (RC)), can also decrease the amount of landfilled C&D waste. The use of RC still faces adoption barriers. In this research, we examined the factors driving the adoption of recycled products for a CE in the C&D sector by focusing on RC for structural applications. We developed a behavioural framework to understand the determinants of architects’ decisions to recommend RC. We collected and analysed survey data from 727 respondents. The analyses focused on architects’ a priori beliefs about RC, behavioural factors affecting their recommendations of RC, and project-specific contextual factors that might play a role in the recommendation of RC. Our results show that the factors that mainly facilitate the recommendation of RC by architects are: a senior position, a high level of RC knowledge and of the Minergie label, beliefs about the reduced environmental impact of RC, as well as favourable prescriptive social norms expressed by clients and other architects. We emphasise the importance of a holistic theoretical framework in approaching decision-making processes related to the adoption of innovation, and the importance of the agency of each involved actor for a transition towards a circular construction sector.

Extended theory of planned behaviour for promoting construction waste recycling in Hong Kong

Changing individual's recycling attitude and behaviour is of utmost importance in achieving sustainable construction and demolition (C&D) waste management, yet it has often been underachieved. To understand the motivations for recycling, this study identifies and prioritizes the key factors that affect C&D waste recycling behaviour of various stakeholders in Hong Kong (i.e., representatives from construction-waste-related organizations, environmental consultants and contractors, and government engineers) in a quantitative manner using statistical tools. Different from traditional C&D waste behavioural determinants studies, this paper utilizes an integrated analytical method through semi-structured interviews and survey questionnaire on the basis of Theory of Planned Behaviour (TPB). Qualitative thematic analysis and quantitative frequency analysis were performed to analyse responses from semi-structured interviews and questionnaires, followed by correlation analysis to quantify the relationships between factors. Results indicated that four key factors: (i) regulatory compliance, (ii) economic incentives, (iii) accreditation scheme, and (iv) logistics and management incentives directly influenced recycling behaviour of individuals. Regulatory compliance was the most determining factor for consultants, contractors, experts, and government officials, whereas economic incentives were of great concern to the public. Under the factor of economic incentives, strong positive relationships were identified between disposal costs and collection and sorting costs, thus increasing waste disposal charging fee may promote recycling behaviour. In comparison, accreditation scheme deserved better recognition to facilitate a closed-loop material flow in the construction industry. These findings help to devise more effective and stakeholder-oriented policy tools to raise awareness and encourage behavioural change towards C&D waste recycling, and assist policy makers to establish regulations and practices for sustainable resource management.

Quantifying demolition fitout waste from Australian office buildings

Purpose

The short life cycle replacement of fitout in modern high-rise office buildings represents an under-researched waste problem. This paper aims to quantify the amount of demolition waste from office strip-out including attention to waste streams going to landfill, reuse and recycling.

Design/methodology/approach

Quantitative waste data (by weight) were measured from 23 office fitout projects situated in “A” grade office building stock from the Sydney CBD. Waste streams were measured separately for landfill, reuse and recycled materials. Descriptive and clustering statistics are presented and analysed.

Findings

From a total of 9,167 tonnes office fitouts demolished, 5,042 tonnes are going to landfill. The main contributor to landfill stream is the mixed waste generated in a fast-track demolition process. This approach partly resulted from the office interiors lacking regularity and easy disassembly. Moreover, considerable variability is observed in the waste per area, the waste streams and the waste compositions. Also, it is noteworthy that the recycled waste stream considerably increases when there exist economically viable conversion facilities, as for metals, hard fills and plasterboards.

Research limitations/implications

The research is focused upon work practices that take place in Australia; therefore, generalisability is limited to situations that have similar characteristics. Future studies are needed to verify and extend the findings of this research.

Practical implications

A key area arising from the research findings is the need to design fitout with recycling and reuse in mind to divert more from landfill. This must explore and incorporate onsite demolition processes to ensure the design is well suited to commercially dominant processes in the overall demolition process, as well as attention to developing economies of scale and viability in re-sale markets for reused items.

Originality/value

Little empirical or quantitative research exists in the area of office fitout waste. This research provides entry to this area via quantifiable data that enables comparison, benchmarking and diagnostic ability that can be used to underpin strategic solutions and measurement of improvements.

Silicate production and availability for mineral carbonation

Atmospheric carbon dioxide sequestered as carbonates through the accelerated weathering of silicate minerals is proposed as a climate change mitigation technology with the potential to capture billions of tonnes of carbon per year. Although these materials can be mined expressly for carbonation, they are also produced by human activities (cement, iron and steel making, coal combustion, etc.). Despite their potential, there is poor global accounting of silicates produced in this way. This paper presents production estimates (by proxy) of various silicate materials including aggregate and mine waste, cement kiln dust, construction and demolition waste, iron and steel slag, and fuel ash. Approximately 7-17 billion tonnes are produced globally each year with an approximate annual sequestration potential of 190-332 million tonnes C. These estimates provide justification for additional research to accurately quantify the contemporary production of silicate minerals and to determine the location and carbon capture potential of historic material accumulations.

Architects' perspectives on construction waste reduction by design

The construction, demolition and excavation waste arising in England was estimated at 91 million tonnes in 2003. The current thinking on construction waste minimisation is heavily focussed on several issues relating to physical construction waste and recycling guides. Indeed, much had been published on ways to improve on-site waste management and recycling activities but very few attempts made to address the effect of design practices on waste generation. However, there is a consensus in the literature that the architect has a decisive role to play in helping to reduce waste by focussing on designing out waste. This paper examines previous studies on architects' approach towards construction waste minimisation; and by means of a postal questionnaire, investigates: the origins of waste; waste minimisation design practices in the UK; and responsibilities and barriers within the UK architectural profession. The findings reveal that waste management is not a priority in the design process. Additionally, the architects seemed to take the view that waste is mainly produced during site operations and rarely generated during the design stages; however, about one-third of construction waste could essentially arise from design decisions. Results also indicate that a number of constraints, namely: lack of interest from clients; attitudes towards waste minimisation; and training all act as disincentives to a proactive and sustainable implementation of waste reduction strategies during the design process.