Sustainability assessment integrating BIM and decision-making for modular slab construction against conventional cast-in-situ

Modular construction is an emerging technique being adopted with varying levels of modularization. Assessing its sustainability performance during the planning phase is essential for deciding between precast elements and traditional cast-in-situ methods. To address this, this study developed a comprehensive sustainability assessment framework that integrates economic, environmental, and social indicators. A total of 26 indicators were extracted from the literature and prioritized by 55 experts. Thus, ten indicators were designated critical and quantified for the case of a three-story building using three slab alternatives: cast-in-situ (CIS), I-girder (PIS), and hollow core (PHS). BIM analyses and qualitative data for the ten sustainability criteria were configured into a decision matrix through a multicriteria decision-making approach, i.e., TOPSIS. Simulations were conducted on the matrix by varying the weights of sustainability domains (0.33 – 0.80) to prioritize the best alternative. The BIM analyses revealed significant advantages of PIS, including a 33% and 31% reduction in material and labor costs, respectively, compared to the CIS. Furthermore, precast elements show a 60% reduction in carbon emissions, a 95% decrease in wastage, and an additional benefit of 90% less air pollution. The TOPSIS simulations concluded the PIS system as the most sustainable alternative with the highest relative closeness coefficients (RCC) in all domains and weight cases. The PIS performed best in the environmental with RCCs of 0.83 – 0.97, then in the economic with 0.83 – 0.86, and with 0.69 – 0.83 in the social domain.