预湿水泥浆颗粒内养护材料对混凝土早期自收缩及抗压强度的影响

制备不同粒径和水灰比的水泥浆颗粒作为低水灰比混凝土内养护材料.以最佳内养护水灰比原则,设计了使用三种水灰比分别为0.6、0.7和0.8的同粒径水泥浆颗粒等体积取代砂子的混凝土.研究了不同水灰比水泥浆颗粒对混凝土早期自收缩、抗压强度和内部微结构的影响.结果表明:颗粒吸水率与其水灰比正相关、与其粒径负相关;预湿水泥浆颗粒可显著降低混凝土早期的自收缩,颗粒水灰比越大,自收缩降低效果越明显;但是掺入水泥浆颗粒也会降低混凝土的抗压强度,颗粒水灰比越高抗压强度降低越多,应用中应优化选择预湿颗粒的水灰比;水泥浆颗粒作为高性能混凝土内养护材料,可改善微观界面的孔隙结构,提高界面的密实性,减少混凝土早期的收缩和开裂.

Influence of Internal Curing by Pre-wetted Cement Particles on the Early-aged Autogenous Shrinkage and Compressive Strength of Concrete

Cement paste particles with different particle size and water-cement ratio were prepared as internal curing ( IC) material of concrete with low water-cement ratio.Three kinds of concrete was designed based on the optimum IC water to cement ratio, which sand is replaced by equal volume with the same size of cement paste particles with different water-cement ratio of 0.6, 0.7 and 0.8.Influence of cement paste particles with different water-cement ratio on the early-age autogenous shrinkage, compressive strength and microstructure of concrete was investigated.The results show that the water absorption rate of particles is positively correlated with the water-cement ratio and negatively correlated with particle size.Pre-wetted cement particles can significantly reduce the early-age autogenous shrinkage of concrete, and the autogenous shrinkage decreases with the increase of the water-cement ratio of particles.However, the mixing of pre-wetted particles will reduce the compressive strength of concrete, the compressive strength of concrete decreases with the increase of water-cement ratio of particles, the water-cement ratio of the IC particles should be optimized in the application.As the IC material of concrete, Cement paste particles can improve the pore structure of micro-interface, increase the compactness of the interface and reduce the autogenous shrinkage of concrete in the early-age.