Study on the Mechanical Influence of Water Ash Ratio and Sand Ratio on the Compressive Strength of Alkali Excited Concrete

In this study, the cement-based material system with different water-cement ratio, and studied the cracking behaviour of the early age of concrete material under the joint influence of constraint shrinkage and stress relaxation. The main work and conclusions are as follows: through the mechanical properties test at early age, self-contraction test, The mechanical properties of four different water-cement ratios (0.17,0.26,0.35,0.52) and self-shrinkage with age, Master the law of water-ash ratio affecting the mechanical properties and self-contraction in early age, It covers the difference in the development of high and low water ash than early age, Mainly because the low water cement ratio in the rapid hydration phase will produce a lot of shrinkage strain in the gel material, Which tains plastic contraction that does not cause stress and effective self-contraction that leads to stress generation, The shrinkage development of high water cement material is relatively stable in this stage. The determination of Time-zero is one of the key problems in the calculation of stress in the early age of low water ash ratio materials. Most self-shrinkage of low water ash ratio materials occurs before Time-zero. At this time, mechanism and the calculation of contraction related data, the method proposes the starting point of self-contraction induced stress through the temperature rate, self-contraction rate and self-contraction development curve. In the internal relative humidity is less than 100% greater than 50%, capillary tension is the main contraction driving force, this is the scholar’s consensus, when the relative humidity is less than 50% and more than 11%, surface tension and dismantling pressure into the contraction driving force, when the relative humidity is less than 11%, gel water loss between CSH layers, led to the late contraction. Early self-contraction often occurs at the water loss stage with RH>70% and is mainly explained by capillary tension theory.