Influence Of Particle Size Distribution Of Mineral Admixture On Shrinkage Of Cement Stone

With the deepening of the research on the durability of concrete,people find that cracking is an important cause of its durability deterioration.It was found that the cracking of concrete reduces the resistance to external corrosive media,and thus the durability is reduced,and shrinkage is the main cause of concrete cracking.Therefore,the study of shrinkage has great theoretical and practical significance for reducing the cracking of concrete and increasing the structural durability.The shrinkage of concrete is mainly caused by the shrinkage of cement stone,studies have shown that the mineral admixture has a great influence on the shrinkage of cement stone,the focus of this article is the effect of grain-size-matched cement stone shrinkage on mineral admixtures.After studying the effects of fly ash and slag mineral admixtures on the shrinkage of cement paste,the influence of water-binder ratio and curing time on shrinkage was further studied.By adjusting the mix ratio,the shrinkage of the cement paste with different mix ratios was compared and analyzed.To explore the shrinkage of cement pastes with different mix ratios,a self-developed shrinkage test device was used.At a temperature of(20±1)°C and a relative humidity of(60±5)%,I studied the 28 d contraction value of a cement paste with a water/binder ratio of 0.3 and a blend of fly ash and ground granulated slag with different fineness and proportions.Among them,fly ash and ground granulated slag took 50 %,60 %,70 % and 80 % of the total mass substitution.The diameter of the cylindrical paste sample was 36 mm and the height was 240 mm.Choose two groups with better particle grading ratio,the effect of water glue ratio and curing time on the shrinkage performance of cement slurry was further investigated.The results showed that the particle size distribution of mineral admixtures has a great impact on the shrinkage of cement stone.The cement paste with greater particle size distribution has less shrinkage.When the content of mineral admixture is 60 %,the improvement of particle size distribution has the greatest impact on the shrinkage of cement stone.The shrinkage of cement paste with ultra-fine fly ash and coarse slag is significantly smaller than that with ultra-fine slag and coarse fly ash.This shows that the addition of ultra-fine fly ash plays a role in the cement paste as a Micro-aggregate filling effect,which improves particle size distribution of cementitious materials and reduces fine pores,so that the contraction is reduced.Water-binder ratio has a great influence on the shrinkage of cement stone.When the mineral admixture content is different,the effect of water-binder ratio on cement shrinkage is consistent,that is,the smaller the water-binder ratio,the smaller the shrinkage of cement stone.The effect of curing time on contraction of cement stone is also significant.The longer the curing time,the smaller the contraction of cement stone.