Influence Of Aggregate-To-Cement And Water-To-Cement Ratios On The Workability Of Concrete Mixes
Samuel Chibuzor Nwoke
Department of Building Technology, Port Harcourt Polytechnic, Rivers State, Nigeria
Ikechukwu Ebuka Amadi
Department of Building Technology, Port Harcourt Polytechnic, Rivers State, Nigeria
Abstract
The workability of fresh concrete is a vital property that influences its placement, compaction, and finishing. It is typically defined by characteristics such as consistency, mobility, and compactability. This study investigates the influence of Aggregate-to-Cement (AG/CM) and Water-to-Cement (W/C) ratios on the workability of concrete. A series of mix compositions labeled MC1 to MC6 were prepared, each with varying AG/CM ratios (6.1 to 2.1) and W/C ratios (0.6 to 0.38). Workability was assessed using Slump, Compacting Factor, and Modified Vebe tests, conducted under controlled ambient conditions (26–30°C temperature, 92% relative humidity, and minimal wind).
The results show a consistent trend: as AG/CM and W/C ratios decrease, both slump and compacting factor values increase, indicating improved workability. Conversely, Vebe time increases with higher AG/CM and W/C ratios, suggesting greater difficulty in compacting these mixes. The findings demonstrate that mixes with AG/CM ≤ 3.0 and W/C ≤ 0.45 exhibit better compaction characteristics and are more workable. Notably, at W/C ratios of 0.45–0.40 and AG/CM ratios of 3.0–2.5, the concrete displayed optimum workability, with slumps ≥100 mm and compacting factors around 0.95, while remaining cohesive and consistent.
Additionally, regression analysis revealed strong correlations between workability parameters and mix ratios, with R² values of 96.7% (Slump–AG/CM), 98.8% (Slump–W/C), 99.4% (Compacting Factor–AG/CM), 99.3% (Compacting Factor–W/C), 99.1% (Vebe Time–AG/CM), and 99.4% (Vebe Time–W/C). These high coefficients indicate clear and predictable relationships, confirming the significance of AG/CM and W/C ratios in determining concrete workability. The study concludes that concrete mixes with reduced AG/CM and W/C ratios—within identified thresholds—yield superior workability and performance in fresh concrete applications.