Experimental Study on the Mechanical Performance of Pumice Stone Lightweight Concrete

The growing demand for sustainable and eco-efficient construction materials has encouraged the exploration of lightweight concrete alternatives that reduce dead load and environmental impact while maintaining adequate structural performance. In this study, pumice stone, a naturally occurring porous volcanic rock, was utilized as a partial replacement for conventional coarse aggregate to develop lightweight concrete mixes of grades M20 and M25. The objective was to evaluate the influence of pumice substitution levels of 0 %, 10 %, 20 %, and 30 % on the workability, compressive strength, split tensile strength, and flexural strength of concrete. Experimental investigations revealed that workability decreased progressively with increasing pumice content due to the material’s rough surface texture and high water absorption capacity. However, up to 10 % replacement, the slump values remained within acceptable limits for standard concrete applications (85 mm for M20 and 80 mm for M25 at 0 %, reduced to 78 mm and 73 mm respectively at 10 %). The compressive strength exhibited a marginal improvement at 10 % pumice replacement, recording 22.3 N/mm² (M20) and 27.2 N/mm² (M25) at 28 days, comparable to control mixes. Beyond this level, strength reduction was observed, mainly attributed to the lower crushing strength and higher porosity of pumice aggregates. Similarly, the split tensile and flexural strengths showed trends consistent with compressive strength, with moderate decreases at higher replacement levels. The overall density reduction of 10–15 % confirmed the lightweight nature of the developed concrete, making it suitable for non-load-bearing and partially structural applications. The optimum performance was achieved at 10 % pumice replacement, providing a balanced combination of strength, durability, and reduced unit weight.