减缩剂对水泥砂浆及超高性能混凝土收缩性能的影响

Effect of shrinkage reducer on shrinkage properties of mortar and ultra-high performance concrete

研究了不同掺量的减缩剂(SRA)对水泥砂浆塑性收缩开裂、水泥水化热、水泥砂浆毛细管负压的影响,以及SRA掺量(1%、3%、4%)对超高性能混凝土(UHPC)抗压强度和收缩性能的影响。结果表明:SRA可显著降低水泥砂浆的开裂面积、平均和最大裂缝宽度,当SRA掺量为4%时,缓解塑性收缩开裂的效果最佳,开裂面积、平均和最大裂缝宽度与基准组相比分别降低了52.1%、35.0%和48.4%;SRA通过延缓毛细管负压的发展,降低了水泥砂浆的塑性收缩开裂;随着SRA掺量的增加,UHPC的抗压强度提高越明显,UHPC的收缩显著降低;当减缩剂掺量为4%时,UHPC的28 d抗压强度达140.0 MPa,收缩率最低。

The effects of different contents of shrinkage reducer(SRA)on plastic shrinkage cracking of cement mortar,heat of hydration of cement,and negative capillary pressure of cement mortar were studied.The effects of SRA content(1%,3%and 4%)on the compressive strength and shrinkage properties of ultra-high performance concrete(UHPC)were investigated.The results show that SRA can significantly reduce the cracking area,average and maximum crack width of cement mortar.The best effect of mitigating plastic shrinkage cracking is achieved when the SRA content is 4%,and the cracking area,average and maximum crack widths are reduced by 52.1%,35.0%and 48.4%,respectively,compared with the baseline group.SRA reduces the plastic shrinkage cracking of cement mortar by delaying the development of capillary negative pressure.With the increase of SRA content,the compressive strength of UHPC improves significantly,and the shrinkage of UHPC decreases significantly.When the content of shrinkage reducer is 4%,the 28 d compressive strength of UHPC reaches 140.0 MPa,with the lowest shrinkage rate.