Comparative performance evaluation of quartz and snail shell powders modified concrete: Mechanical, machine learning, and microstructural assessments

Abstract

This paper presents the effect of snail shell powder (SSP) and quartz powder (QP) as a partial replacement of cement to reduce the impact on the environmental footprint of concrete. The study assesses fresh, mechanical, non-destructive, and microstructural properties of SSP and QP contents at 2.5-10% as a supplementary cementitious material (SCM) in the development of eco-friendly concrete. The SSP particles are flaky-irregular and contain 59.8% CaO, which is found suitable as an SCM. The incorporation of SSP and QP gradually reduced slump, compacting factor, and Kelly ball penetration of the concrete mixtures. The 28 days compressive, tensile, and flexural strength of the control specimen are 43.5 MPa, 4.45 MPa, and 7.52 MPa, respectively. The relative compressive, tensile, and flexural strengths of concrete containing 7.5% SSP are 125%, 120%, and 112%, respectively, of control concrete, and these values are higher compared to the 7.5% QP as a partial replacement of cement. A similar strength development trend is confirmed from the ultrasonic pulse velocity and rebound hammer index tests. Later, the extreme gradient boosting ML algorithm provided a nominal coefficient of determination of 0.988 in the prediction of compressive strength of concrete compared to the gradient boosting and random forest model. Finally, scanning electron microscopy on the hardened samples indicated a consistent development of dense microstructure by reducing voids and cracks over the testing period. As seen by adding the optimal SSP replacements of eco-friendly concrete mixtures, it boosted mechanical strength while lowering carbon footprint, making it a sustainable building concrete construction.

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