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.

Green remediation of contaminated sediment by stabilization/solidification with industrial by-products and CO2 utilization.

Navigational dredging is an excavation of marine/freshwater sediment to maintain channels of sufficient depth for shipping safety. Due to historical inputs of anthropogenic contaminants, sediments are often contaminated by metals/metalloids, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and other contaminants. Its disposal can present significant environmental and financial burdens. This study developed a novel and green remediation method for contaminated sediment using stabilization/solidification with calcium-rich/low-calcium industrial by-products and CO2 utilization. The hydration products were evaluated by quantitative X-ray diffraction analysis and thermogravimetric analysis. The incorporation of calcium carbide residue (CCR) facilitated hydration reaction and provided relatively high 7-d strength. In contrast, the addition of Class-F pulverized fly ash (PFA) and ground granulated blast furnace slag (GGBS) was beneficial to the 28-d strength development due to supplementary pozzolanic and hydration reactions. The employment of 1-d CO2 curing was found to promote strength development (98%) and carbon sequestration (4.3wt%), while additional 7-d air curing facilitated cement rehydration and further carbonation in the sediment blocks. The leachability tests indicated that all studied binders, especially CCR binder, effectively immobilized contaminants in the sediments. The calcium-rich CCR and GGBS were regarded as promising candidates for augmenting the efficacy of CO2 curing, whereas GGBS samples could be applicable as eco-paving blocks in view of their superior 28-d strength. This study presents a new and sustainable way to transform contaminated sediment into value-added materials.