Assessment of the influence of the effective water-cement ratio on the workability and strength of a commercial concrete used for the construction of concrete caissons

The aim of this research is to assess the influence of the effective water-cement ratio on the concrete workability and strength. This study was carried out with a concrete used for the manufacture of concrete caissons for the construction of a harbour in the south of Tenerife. This commercial concrete was elaborated with basaltic aggregates but with a partial replacement of basalt sand by a sand called "African Sand". As a reference, a concrete containing only basaltic aggregates was manufactured. The water absorption of the aggregates influence the amount of water available for the hydration of the cement. The value of water absorption for the basaltic sand is higher than African sand. This presence of aggregates with different water absorption in the concrete allowed the proposal of a methodology for the determination of the effective water-cement ratio in the fresh concrete. This methodology was used for the calculation of water available for the hydration of the cement in the fresh concrete. The results allowed the answer for two questions regarding the behaviour of these concrete mixes. Firstly, how the incorporation of this African sand influences effective water-cement ratio and the concrete workability. Secondly, how this incorporation influences the strength of the concrete.