Effects and threshold of water film thickness on multi-mineral cement paste

In this study, the effect of the water film thickness (WFT) on unary, binary, and ternary mixtures containing cement, basalt powder (BP), and zeolite powder (ZP) were investigated. The correlations between the WFT and the flow parameters, rheological parameters, cohesiveness, and bleeding rate were investigated using statistical methods. The experimental results showed that the addition of ZP or BP could increase the paste's packing density and cohesiveness and reduce the bleeding rate. A good rheological performance and high hardened compressive strength could be achieved simultaneously with suitable substitutions. The correlation coefficient of the WFT vs. the bleeding rate of the multi-mineral cement paste obtained by statistical analysis increased with time due to the physical process of particle settling. The WFT and flow parameters, such as the flow spread and flow rate, of the multi-mineral cement paste could be precisely described by by a single function. In-depth analysis indicated that there was a threshold value of the WFT that could be used to distinguish the effects of ZP and BP on the rheological parameters of the cement paste. This represents the critical point at which the mineral admixture loses its morphological effect on the flow performance of the cement paste. The existence and conditions for this threshold value were further proven by theoretical analysis based on the Brownian, gravitational, and colloidal attraction forces.