Unlocking the role of water on the early age strength development of zero-slump concrete: Prediction of the optimal water content

Zero-slump concrete (ZSC) with low water and binder contents must develop sufficient early-age strength to withstand outdoor stacking loads. However, rational mix design remains challenging because the role of water content in early-age compressive strength development is not yet clearly understood. This study aims to investigate the role of water content in the early-age compressive strength development of ZSC. Experimental results demonstrate that, at a given packing density (PD), compressive strength of ZSC evolves through three distinct stages with increasing water volume: an increasing stage, a flattening stage, and a decreasing stage, which differs from the behavior of conventional concrete. A solid particle distribution model is proposed to explain the mechanisms governing this development, attributing it to water-induced variations in cement particle spacing and autogenous shrinkage. Based on this model, a prediction method is developed and validated across different ZSC mix designs. Overall, the findings provide a unified mechanistic framework for a practical mix design approach to optimize water content and mitigate its detrimental effects on compressive strength development in ZSC.