Regulation Mechanism of Maximum Paste Thickness in Pervious Concrete: Rheological Function Modeling, Aggregate Morphology Influence, and Additive Enhancement

The cement paste thickness (CPT) has a direct and key impact on the mechanical properties and permeability of pervious concrete. The influence of CPT on the pore structure and seepage characteristics of pervious concrete was analyzed in this study. The combination of basket-immersion method and 3D reconstruction technology using computed tomography and Avizo software was used to measure the specific surface area of aggregates, and sieve mesh filtration method was designed to quantify the maximum paste thickness (MPT). The relationship between the rheological properties of cement paste and MPT was established. At the same time, the effect of aggregate morphology and additives (silica fume and nanosilica) on MPT was also explored. The results show that the relationship between MPT and cement paste fluidity and the relationship between MPT and cement paste viscosity can be described using single exponential decay function and Boltzmann function, respectively. For the same batch of aggregates with similar texture and water absorptions, the larger the sphericity of aggregates, the smaller the MPT. Silica fume and nanosilica can adjust the rheology of cement paste, significantly improving MPT. This study can offer a guide for controlling MPT in the mix design of pervious concrete.