Direct and indirect carbon emissions in foundation construction – Two case studies of driven precast and cast-in-situ piles

Abstract

Precast technique has gained significant reputation in the construction industry due to improved efficiency and reduced construction waste. Pile foundation is often built through driven precast or cast-in-situ construction technique. The two types of pile foundations have been widely utilised in various building construction types. The selection of the piling methods has been largely based on the project scope, soil conditions and availability of resources. However, little research has been conducted on environmental impacts brought by driven precast piles compared to cast-in-situ bored piles. The paper aims to address the research gap by conducting a comparative study to measure greenhouse gas (GHG) emissions of driven precast and cast-in-situ piles construction using two case studies in China. A process-based quantification model is developed to measure the major emissions and impacts due to materials, transportation and equipment usage. Results of the study indicated 113.04 and 107.46 kgCO2 per pile per metre of excavated depth for case study A and B respectively. Results of the study also observed a reduction for equipment usage and an increase for transportation in GHG emissions for driven precast piles as compared to cast-in-situ piles. Four scenarios were selected to further investigate the GHG emissions variation. Results indicated that use of sustainable materials can achieve the maximum GHG emissions reduction for both types of pile construction. Transportation distance was recorded as a key factor to be considered in reducing GHG emissions for driven precast piles construction. Results of the study can be effectively utilised to compare life cycle GHG emissions of precast construction with cast-in-situ construction.