Experimental Evaluation of Concrete Incorporating Processed Overburden Sand from Lignite Mines as Sustainable Fine Aggregate

Abstract

The high demand of natural river sand for concrete production has led to its rapid depletion and increased the necessity to explore sustainable alternatives to fine aggregates. The overburden materials generated during open cast mining have emerged as an abundant resource with significant potential for beneficial utilization. The current research aims at examining the suitability of processed overburden sand (POBS) derived from lignite mine overburden as a substitute for natural river sand in concrete at replacement levels of 20%, 40%, 60%, 80% and 100%. Fresh concrete characteristics were determined using slump test, Vee-Bee test, and flow table tests. Hardened concrete properties including compressive strength, flexural strength, stress-strain characteristics, modulus of elasticity, and durability parameters like water absorption, sorptivity, acid resistance, sulphate resistance, and salt resistance were studied. Workability decreased progressively with increasing POBS content, while all mixes maintained acceptable values for medium workability concrete production. Hardened properties showed a modest reduction up to 60% replacement, beyond which the rate of reduction became marginal. A similar trend was observed in durability performance. All mixes, including 100% POBS, satisfied the strength requirements of M20 grade concrete. The 60% replacement level was identified as optimal, providing a balanced performance in terms of strength, workability, and durability. The observed behavior is attributed to the gradation and morphology of POBS. Overall, the results demonstrate that POBS is a feasible and sustainable substitute to natural river sand in concrete.