A Comparison of Material Quantities Estimates to Onsite Material Use for Bridge Infrastructure Projects

Abstract

Material estimates play a crucial role in predicting project cost, project duration, and embodied CO2e emissions for construction projects. Several factors that occur during the implementation stage introduce discrepancies in material quantity estimates, which misinform critical decisions that affect project delivery. There is, however, a limited understanding of the variability in material estimates for construction projects, and its impacts on other estimating processes. This thesis compares construction stage quantities to detailed design estimates for eighteen Canadian-based bridges to quantify the variability in material quantities and to determine the driving factors. Results show a 3%-85%, 8%-23%, 5%-19%, and 11%-17% increase in concrete, rebar, structural steel, and asphalt quantities between estimates and onsite use. The results of this thesis inform our understanding of design estimates and their interpretation. Adjusting for the discrepancy between estimates and onsite measurements and targeting the driving factors will reduce environmental impacts, minimize cost overruns and limit delays.