不同化学结构高吸水树脂对砂浆稠度及自收缩的影响

The influence of superabsorbent polymers with different chemical structures on the consistency and self-shrinkage of cement mortar

测试了不同化学结构的聚丙烯酸-丙烯酰胺类高吸水树脂(SAP)分别在自来水及饱和氢氧化钙溶液中的吸液特点,在固定初始稠度的基础上,分析了几种SAP在砂浆中的真实吸液情况,并探讨了其对砂浆自收缩和孔隙结构的影响。结果表明,随着丙烯酰胺含量的增加,SAP在自来水中的吸水率下降,但在饱和Ca(OH)2溶液中的吸液率显著提升;相同初始稠度情况下,丙烯酰胺含量最高的SAP在砂浆中快速达到吸液平衡,对砂浆贯入度的经时损失影响相对最小;额外引水后,丙烯酰胺含量最大的SAP对砂浆的内养护效果最好,对28 d砂浆自收缩的减缩率可达62.53%;压汞结果表明,相同水灰比时,SAP对孔径小于100 nm的孔隙影响较小,总水灰比是决定砂浆孔隙率的最主要因素。

In this paper,the liquid absorption characteristics of polyacrylic acid-acrylamide superabsorbents(SAP)with different chemical structures were tested in tap water and saturated calcium hydroxide solution respectively,and the real properties of several SAPs in mortar were analyzed under the condition of fixed initial consistency,and the influence of several SAPs on the self-shrinkage and pore structure of mortar was discussed.The results showed that with the increase of acrylamide concentration,the absorption capacity of SAP in tap water decreases,while that in saturated Ca(OH)2 solution increased significantly.Under the same initial consistency,the SAP with the highest concentration of acrylamide can quickly absorb and balance in the mortar,and has the smallest effect on the loss of mortar penetration over time.By adding additional curing water to the mortar mixture,the group containing SAP with the largest amount of acrylamide showed the smallest self-shrinkage strain value,and the shrinkage rate at 28 d turned out to be 62.53%.In addition,the mercury intrusion results show that SAP has little effect on the pores with a pore diameter of less than 100 nm when it is the same as the water-cement ratio,and the total water-cement ratio is the most important factor determining the porosity of the mortar.