Influence of Water-Cement Ratio on Compressive Strength of Concrete Used in Road Construction in Ondo State

The water-cement ratio is one of the most critical mix design parameters governing the compressive strength and durability of concrete pavement structures. This study investigates the influence of varying water-cement ratios on the compressive strength of concrete mixes used in road construction projects in Ondo State, in the South West geopolitical zone. Laboratory specimens were cast at water-cement ratios of 0.40, 0.45, 0.50, 0.55, and 0.60, using locally sourced aggregates from Akure and Ondo Town quarries. Standard cube compressive strength tests were conducted at 7, 14, and 28 days in accordance with BS EN 12390-3. Additionally, concrete samples were collected from three ongoing road construction sites to characterise the mix proportions and water content employed by contractors. Results demonstrate a consistent inverse relationship between water-cement ratio and 28-day compressive strength across all mixes, with a reduction from 38.2 N/mm2 at a ratio of 0.40 to 21.7 N/mm2 at a ratio of 0.60. Site-collected samples yielded an average ratio of 0.58, corresponding to compressive strengths inadequate for heavy vehicular pavement applications. The study attributes the high field water-cement ratios primarily to workability demands in the absence of admixture use and inadequate contractor supervision. Recommendations include mandatory use of plasticisers to achieve workability at lower water contents and systematic concrete quality control procedures during road construction. Keywords: water-cement ratio, compressive strength, concrete pavement, Ondo State, road construction.