Low carbon concrete for prefabricated modular construction in circular economy: an integrated approach towards sustainability, durability, cost, and mechanical performances

The construction industry accounts for significant global resource consumption and carbon emissions through cement production, concrete mix design and building operation, which can be affected by the constituent composition, mechanical and thermal performance of concrete mix. Prefabrication and circular economy nowadays can be a game-changer for the construction industry. This study investigates the effects of concrete mix design on the sustainability, carbonation-induced durability, cost, and mechanical performances of a standard module of prefabricated modular construction throughout the whole life cycle in circular economy. Sixteen concrete mixes, including ordinary Portland cement (OPC) concrete blended with supplementary cementitious materials, ultra-lightweight cement composite (ULCC) with calcined clay and limestone replacement, and foam concrete, are examined. Comprehensive life cycle cost, mechanical, durability and sustainability assessments are conducted for the concrete mixes, considering expected service lives of 50, 100, and 150 years. Results indicate that prolonging service life from 50 years to 150 years in circular economy can improve the annual sustainability performances by up to 20%. Utilizing lightweight concrete (ULCC and foam concrete) can reduce energy consumption for air-conditioning by 17% and decrease transportation-related costs by from 30% to 15%. ULCC mix demonstrates superior overall performance due to its reduced weight, low thermal conductivity, and enhanced durability, showing improvements up to 25% compared to OPC concrete.