Effect of pre-soaked superabsorbent polymer on shrinkage of high-strength concrete
Effect of pre-soaked superabsorbent polymer on shrinkage of high-strength concrete
复制标题
预浸高吸水性聚合物对高强混凝土收缩的影响
DOI：
10.1617/s11527-014-0351-2
复制
发表时间：
2015-09-01
影响因子：
3.8
通讯作者：
Lu, Zi-chen
中科院分区：
文献类型：
--
作者：
Kong, Xiang-ming;Zhang, Zhen-lin;Lu, Zi-chen
将预浸型高吸水性树脂作为内养护剂掺入高强混凝土中，研究其对混凝土早期收缩和力学性能的影响。在基于毛细管应力的混凝土收缩预测模型的基础上，结合水泥水化动力学、内部温湿度演变、孔结构演变和力学性能的试验结果，对SAP的作用机理进行了探讨。结果表明，预浸保水剂的掺入显著降低了高强混凝土在干燥条件下的自收缩和早期收缩。在密封的高强混凝土试件中，由于自干燥效应引起的内部湿度的下降被预浸液的加入显著延缓。掺入预浸液后，高强混凝土的抗压强度略有降低，这种影响在早龄期混凝土中表现得更为明显。此外，还对预浸保水剂引入的内部养护水和混凝土中添加的自由拌合水的性能进行了深入的比较。结果表明，内养护水和外加拌和水对水泥水化动力学、硬化水泥浆体孔结构和混凝土强度的影响不同，这是由于内养护水和外加拌和水在混凝土体内的空间分布不同。在高强混凝土中掺入额外的内养护水，对高强混凝土的减缩效果远强于外加拌和水的效果。此外，内养护水的强度折减效果远不如外加拌和水。根据收缩预测模型，从以下两个方面提出了预浸保水剂降低高强混凝土自收缩的作用机理。内部养护水参与水泥水化过程，导致硬化水泥浆体总体积增大。同时，预浸保水剂内部固化水的释放延缓了内部湿度的下降。这两种因素的协同作用有效地降低了高强混凝土的自收缩。
Pre-soaked super-absorbent polymer (SAP) was incorporated into high-strength concrete (HSC) as an internal curing agent to study its effects on early-age shrinkage and mechanical properties. On the basis of the capillary stress based model for shrinkage prediction of concrete, together with the experimental results of cement hydration kinetics, evolution of internal temperature and humidity, development of pore structure and mechanical properties, the working mechanism of SAP was discussed. Results indicate that the addition of pre-soaked SAP significantly reduces the autogenous shrinkage as well as the early-age shrinkage of HSC under drying condition. In sealed HSC specimens, the drop of internal humidity caused by the self-desiccation effect is notably postponed by addition of pre-soaked SAP. The addition of pre-soaked SAP slightly reduces the compressive strength of HSCs and this effect is more pronounced in early-age concrete. Furthermore, an insightful comparison of the behaviours of the internal curing water introduced by the pre-soaked SAP and the additional free mixing water in concrete was made. Results indicate that the internal curing water behaves differently from the additional mixing water in influencing the cement hydration kinetics, pore structure of hardened cement pastes and the mechanical strength of concrete, due to the different spatial distribution of the two types of water in the concrete bodies. The shrinkage-reducing effect on HSC due to the addition of extra internal curing water incorporated by pre-soaked SAP is much stronger than that of the additional mixing water. Besides, the internal curing water shows much less strength-reducing effect than the additional mixing water. In virtue of the shrinkage prediction model, the working mechanism of pre-soaked SAP in reducing autogenous shrinkage of HSC is proposed on the basis of the following two aspects. The participation of internal curing water in cement hydration process leads to a total volume gain of the hardening cement pastes. Meanwhile, the release of internal curing water from the pre-soaked SAP postpones the drop of internal humidity. The synergistic effect of these two factors effectively reduces the autogenous shrinkage of HSC.