减缩剂与内养护复合对水泥砂浆性能的影响

Influence of Combination of Shrinkage Reducing Admixture with

关键词:  减缩剂  内养护  轻骨料  收缩  抗压强度

Key words:  shrinkage reducing admixture(SRA)  internal curing(IC)  lightweight aggregate  shrinkage  compressive strength

摘要:

研究了密封和干燥条件下，使用减缩剂、饱和轻骨料内养护以及两者复合使用对砂浆收缩、水化以及抗压强度的影响.结果表明：密封条件下，较减缩剂和内养护单独使用，两者复合使用能进一步抑制砂浆内部相对湿度的下降，进而使体系自收缩发展速率和水平显著降低，砂浆7d内保持微膨胀状态，28d自收缩率低于100×10-6；干燥条件下，相比仅使用内养护，复合减缩剂后砂浆干燥收缩明显降低，但由于内养护使砂浆失水量增大，复合减缩剂后减缩效果不及仅使用减缩剂的砂浆；两者复合使用后能够显著降低减缩剂单独使用时对水泥水化和砂浆强度的不利影响.

Abstract:

Influence of shrinkage reducing admixture(SRA), internal curing(IC) by using saturated lightweight aggregate, and SRA combined with IC on shrinkage, cement hydration and compressive strength of cement mortar cured under sealed and drying conditions were investigated. For sealed curing, compared with SRA or IC mixtures, when the IC and SRA were used together, the autogenous shrinkage of cement mortar was significantly reduced, which was resulted from the reduction of internal relative humidity drop, a microdilatancy in length was observed in 7d age, moreover, the ultimate autogenous shrinkage of the mortar was below 100×10-6 at 28d age. On the other hand, for drying condition, compared with only using IC, the SRA can significantly enhance the drying shrinkage reduction of internally cured mortar. However, since the moisture loss of internally cured mortar was larger than that of using SRA only, the drying shrinkage of mortar with adding IC and SRA together was greater than that of adding SRA only. Nevertheless, the combination was contributed to the cement hydration and strength development of mortar compared with that of using SRA only.