减缩剂对水泥基材料减缩效果的研究

Effect of shrinkage reducing agent on shrinkage of cement based materials

综述水泥基材料各类常见收缩的特点、机理及对水泥基开裂的影响。通过自由收缩、质量损失、强度、平板抗裂性等试验研究减缩剂(SRA)的减缩抗裂效果。加入SRA,砂浆早期收缩明显减小,且减缩率前7d最大。而质量损失早期高于未加SRA的,后期则趋于平缓;SRA降低砂浆抗压、抗折强度。这与SRA降低砂浆孔隙水表面张力、延缓水泥水化、改变孔结构有关。平板抗裂对比试验表明:抗裂效果聚丙烯纤维最好,减缩剂次之,膨胀剂最差。

The dry shrinkage, autogenous shrinkage, chemical shrinkage, plastic shrinkage of cement based materials including the character, mechanism, factors, occurring time, relations and the influence on cracking are summarized firstly. The effect on cement based mortar was studied by experiments including free shrinkage, mass loss rate, strength, fiat-restrained cracking resistance text. The results show： the addition of shrinkage reducing agent （SRA） reduced the early shrinkage significantly, especially in first 7 days. The mass rate of mortar with SRA was higher than that without SRA; The SRA reduced the compressive and flexural strength of mortar. It is because SRA reduces the surface tension of capillary pore water, delays the hydration of cement, and changes the pore structures. The flat cracking resistance text shows： The effect of polypropylene fibers was the best in cracking resistance, and then the SRA, the addition of expansive agent was the worst in the three adopted measures.