Design, procurement and construction strategies for minimizing waste in construction projects
The construction industry contributes the largest portion of waste to landfill, and it consumes a significant proportion of mineral resources excavated from nature. Due to adverse environmental impacts of waste generation, as well as financial gains associated with its minimization, waste intensiveness of the industry has remained a major concern across nations. This study investigates the design, procurement and construction strategies for waste minimization, using a dynamic approach. Apart from an investigation of the key and underlying measures for construction waste mitigation, the study considers the interrelationship between stages of projects' lifecycle. This is as activities carried out at an earlier stage are capable of engendering occurrences at later stages of the dynamic project delivery processes.
Following the tenets of critical realism philosophy and exploratory sequential mixed method, the study combined qualitative and quantitative approaches at intensive and extensive stages respectively. At the early stage of the study, data were collected through literature review and focus group discussions with industry experts. Results of the qualitative study were used to develop a questionnaire, which was analysed using statistical approach and structural equation modelling. As a means of investigating the key drivers of waste minimization at a holistic level, a system dynamic model was developed to simulate the interplay and effects of different strategies that were confirmed through the previous process.
The study suggests that design stage has the most decisive impacts on construction waste minimization. At this stage, the key dimensions for designing out waste include design for modern methods of construction, collaborative design process, design for standardisation and waste-efficient design documentation. Error-free design and involvement of contractors at early design stage are part of the critical success factors for designing out waste. With design being much important for waste minimization, competencies of design in terms of waste behavioural competency, design task proficiency, construction-related knowledge and inter-professional collaborative competency are essential for designing out waste. Materials procurement process could enhance waste minimization by considering its key dimensions for driving waste-efficient projects, which includes waste-efficient materials purchase management, suppliers' alliance and waste-efficient bill of quantity. Efficient materials take-off and take back scheme are confirmed as critical success factors for driving waste minimization through materials procurement processes. During construction activities, waste could be reduced through prefabrication and offsite technology, contractual requirements, maximisation of materials reuse and improved collaboration, among others. Prefabrication, supply chain alliance and collaborative procurement routes are confirmed as the critical success factors for reducing waste during construction process. Dynamic interplay among these sets of strategies suggests that notwithstanding the significance of the different measures during design, procurement and construction processes, prefabrication technology and collaborative procurement route are the holistic drivers of construction waste minimisation.
The study implies that designers could effectively drive waste minimization through dimensional coordination and standardisation of design in line with standard materials supplies. In addition to the need for prefabrication and offsite technologies, increasing collaboration among project team is requisite to reducing waste generated by construction activities. By implementing the strategies suggested in the study, substantial proportion of construction waste would be diverted from landfill.
Ajayi, S. Design, procurement and construction strategies for minimizing waste in construction projects. (Thesis). University of the West of England
|Keywords||construction waste, landfill, design management, structural equation modelling, system dynamic modelling|
Saheed Thesis_Final Copy.pdf