Predicting the Formwork Lateral Pressure of Self-consolidating Concrete Based on Experimental Thixotropy Values

摘要

Self-consolidating concrete (SCC), despite its many positive advantages, increases the formwork lateral pressure of the mixture due to its high fluidity, leading to the increased cost of formwork construction in the in situ concrete structures. The thixotropy property, as the most significant functional feature including the effect of mixture proportions on lateral pressure, was selected to investigate the behavior of fresh concrete in the mold. In the present study, the thixotropy and formwork pressure characteristics (including maximum lateral pressure and pressure drop rate) of 15 SCC mixtures were investigated by considering a number of mixtures proportions variables including cement content, water-to-cement ratio, and mineral admixtures. In addition to studying the effect of these variables on the thixotropy level and the lateral pressure of the formwork, the relationship between the methods of measuring the thixotropy level (hysteresis methods, the area of structural breakdown, and the yield stress growth rate) was evaluated considering the mechanism of these methods. In this study, formwork pressure simulator device was used to measure maximum lateral pressure and lateral pressure drop rate. In addition, the effects of mixture proportioning variables on thixotropy and its relationship with the formwork pressure were studied. Using these indices, the ability to predict the behavior of concrete in the mold was investigated through modeling. The presented predicting model of the formwork pressure based on thixotropy value showed an acceptable correlation coefficient (R-20.77).