EFFECT OF PARTIAL REPLACEMENT OF RIVER SAND WITH QUARRY DUST ON THE WORKABILITY AND COMPRESSIVE STRENGTH OF CONCRETE
The increasing demand for natural river sand for concrete production has created a need for alternative fine aggregates that can reduce dependence on naturally occurring resources while maintaining satisfactory concrete performance. This study investigated the effect of partial replacement of river sand with quarry dust (QD) on the grading characteristics, fresh-concrete workability and compressive-strength development of concrete. River sand was progressively replaced with QD at 0–100% in 10% increments, while the other mix parameters were maintained under the experimental conditions of the study. Aggregate grading was characterized, and the fresh concrete was evaluated using slump and compaction-factor tests. Compressive strength was determined at 7, 14, 21 and 28 days using four replicate specimens for each combination of QD replacement and curing age. The results showed that increasing QD content progressively reduced slump, indicating increasing restriction of fresh-concrete mobility. Compaction factor increased to a maximum at 50% QD replacement before declining at higher replacement levels. Compressive strength followed a similar optimum response: strength increased progressively up to 50% QD and subsequently decreased. The 50% QD mixture recorded the highest mean compressive strengths of 22.65, 24.50, 25.13 and 27.10 N/mm² at 7, 14, 21 and 28 days, respectively, compared with 19.33, 21.20, 22.30 and 24.50 N/mm² for the control concrete. Two-way analysis of variance confirmed highly significant effects of both QD replacement and curing age on compressive strength (p < 0.001), with a significant QD replacement × curing-age interaction. The findings indicate that moderate QD incorporation can provide a favourable balance between aggregate packing and fresh-state behaviour, while excessive replacement becomes detrimental to workability and strength. Under the conditions investigated, 50% QD replacement represents the optimum level.
Keywords: Quarry dust; river sand; concrete; workability; compressive strength; fine aggregate replacement; sustainable construction
