Comparative analysis of concrete strength utilizing quarry crushed and locally sourced coarse aggregates in Jos metropolis

Abstract

This work compares the compressive strength and other physical properties of concrete made with coarse aggregates obtained from machine-crushed and hand-crushed coarse aggregates improvised from Jos Metropolis middlebelt Plateau State Nigeria. The phenomenon of using nonconforming hand-crushed aggregates in local construction which provides variable concrete quality through batching inevitably invalidating structural integrity galvanized the research. Aggregates from three machine crushed sources PW Quarry (Jos South), RicRock Quarry (Jos East) and Moulds Quarry (Jos East) and hand-crushed source: Tudunwada (TW), Building Materials Market (BM) and Domkat Bali (DB). Test were conducted on the rock samples to determine their geological, physical and mechanical properties in accordance with BS 410, BS 812 and BS EN 12520 respectively. The results of sieve analysis shows that machine-crushed aggregates has a 95-95% the 20 mm sieve and 54-58% passing the 12.5 mm sieve which are within the BS EN 12620 grading limit, while the hand-crushed aggregates exhibited below the stipulated gradation. The mechanical properties of the machine-crushed aggregates revealed that LAA ranges from 21.6-23.4%, AIV of 17.5-18.9% and ACV of 19.2-20.4% across all the samples indicating a higher resistance to wear confirming better mechanical performance against the hand-crushed aggregates with LAA of 26.8-28.5%, AIV of 21.7-23.1% and ACV of 23.4-24.9% which are higher and may result to poor concrete bonding. The compressive strength showed that machine crushed aggregate achieved maximum mean strength at 28-days curing with PW having 28.6 MPa, Ricrock with 29.1 MPa and Moulds with 27.4 MPa while Hand-crushed aggregate recorded a lower strength at 28-days curing with TW, BM and DB exhibiting CS of 23.7 MPa, 24.0 MPa and 22.5 MPa respectively. These findings revealed that machine-crushed aggregates yield superior and more consistent concrete quality due to their uniform particle size distribution and reduced flaky content than the hand-crushed aggregates. The study recommends that machine-crushed aggregates should be prioritized for structural applications, while hand-crushed aggregates may be limited to non-structural applications.