Mechanical properties, sorption characteristics, and microstructure of Portland cement concrete containing sulfate-resistant mineral admixture and sugarcane bagasse ash.

This study investigated the impact of sulfate-resistant mineral admixture (SP2) and untreated sugarcane bagasse ash (SCBA) as a partial substitute for cement on the physico-mechanical properties and microstructure of Portland cement concrete. Four concrete mixtures were prepared for the investigation including a control mixture, SP2 mixture (4.7% SP2), SCBA mixture (5% SCBA), and SP2-SCBA mixture (4.7% SP2 and 5% SCBA). The SP2 mixture exhibited superior performance across all assessed engineering properties in comparison to the other mixtures. Moreover, a comparative analysis was conducted to evaluate the performance of untreated SCBA used in this study versus processed SCBA from recent research. Remarkably, untreated SCBA, despite having minimal impact on compressive strength, it demonstrated notable improvements in tensile strength. When combined with 4.7% SP2, the untreated SCBA mixture achieved a remarkable 37.9% increase in splitting tensile strength compared to the control mixture, outperforming similar mixtures using processed SCBA and silica fume in previous studies. Microstructure analysis revealed a large amount of spongy, fibrous hydrated structures in both the SCBA and SP2-SCBA mixtures. These structures provide a rational explanation to the increase in splitting tensile strength of the concrete containing SCBA. The findings highlight the tradeoff between using untreated SCBA and treated SCBA as sustainable cement replacements. Although untreated SCBA can only be used at a low replacement level, it offers unique engineering benefits alongside significant energy savings.