Sustainable mixtures using waste oyster shell powder and slag instead of cement: Performance and multi-objective optimization design

Abstract

• The response surface method (RSM) was used to design an experiment, and a multi-objective optimization analysis was conducted. • The sustainable performance of discarded waste oyster shell (WOS) powder and blast furnace slag (BFS) was investigated through microscopic and macroscopic experiments. • The overall performance of the paste was optimal when the replacement rates of WOS powder and BFS were 5.01% and 25.95%, respectively. • The error between the experimental and model prediction results was < 5 %. The use of supplementary cementitious materials reduces carbon emissions but can affect the performance of concrete. An experimental study was conducted on the performance of waste oyster shell (WOS) powder and industrial byproduct slag as supplementary cementing materials. First, the experiment was designed using Design-Expert® v12 software. Subsequently, macroscopic properties of the pastes were tested, such as their workability, compressive strength, and electrical resistivity. Additionally, the hydration performance and microstructures of the pastes were investigated. Finally, the response surface method was used to perform model analyses, multi-objective optimization, and experimental verification of the workability, cumulative heat of hydration, compressive strength, and electrical resistivity. The experimental results indicated that both WOS powder and slag can significantly reduce the heat of hydration and carbon emissions. Adding a small amount of WOS powder increases the early compressive strength. However, as the substitution amount increases, the compressive strength and ultrasonic pulse velocity decrease. The results of the hydration heat experiments indicated that WOS powder can increase the hydration rate of the paste. Furthermore, WOS powder had no apparent effect on the electrical resistivity, but the synergy with slag increased the electrical resistivity of the paste; the carboaluminate observed in the microstructure analysis confirmed this synergy. Moreover, a normalized comparison of the carbon emissions of the pastes based on the compressive strength suggested that the ternary pastes exhibit good performance with regard to sustainability. The verification test results obtained using the optimized design scheme agreed well with the optimized design’s projected value, with all errors being < 5 %.