Based on the shrinkage problem of high-performance concrete in high-altitude dry environments,the effects of different dosage of the anionic polyacrylamide polyacrylate superabsorbent polymers (SAP-YF)and a commercial polypropylene-based super absorbent polymers (SAPS)on the shrinkage properties of cement-based materials under high-altitude dry environment were studied. The test results showed that with an increase in SAP dosage,the autogenous shrinkage and strength of the cement-based materials gradually decreased,while the drying shrinkage remained relatively unchanged. Considering the premise of not affecting the strength and minimizing shrinkage,the optimal dosage of SAP-YF was 0. 20% under a water-cement ratio of 0. 20,with a shrinkage reduction rate of 28. 21%. XRD and TG results showed that the hydration degree and solid phase composition of the SAP-containing specimens exhibited significant improvements compared to the control group after 7 d of curing. The introduction of SAP helped maintain the internal moisture content of the paste matrix,creating an environment conducive to the hydration of cementitious materials for 7 d or more. The inclusion of SAP accelerated the early hydration process of cementitious materials. Based on XRD,TG experiments,and theoretical research,a model for the evolution of solid-phase composition of cement-based materials containing SAP with curing time under dry conditions was established,which could provide data support for thermodynamic model calculations and concrete mix design in high-altitude dry environments.

摘要 

本工作基于高原干燥环境下高性能混凝土收缩问题,研究了不同掺量的阴离子型聚丙烯酰胺超吸水树脂(SAP-YF)与商用聚丙烯酸型超吸水树脂(SAP-S)对水泥基材料在干燥环境下收缩性能的影响,结果表明,随着SAP掺量的增大,水泥基材料的自收缩与强度逐渐减小,干燥收缩则无明显变化;在考虑不影响强度及最大程度减缩的前提下,SAP-YF在水灰比为0.20条件下的最优掺量为0.20%,减缩率为28.21%;XRD与TG结果表明在养护至7 d时,掺有SAP的试件组的水化程度和固相组成含量的增幅相比于对照组有较为明显的改善。掺入SAP后,净浆试件基体内部的相对湿度能够维持在有利于胶凝材料水化的环境中,可持续7 d或更长时间,从而加速了胶凝材料的早期水化进程。基于XRD、TG试验与理论研究,建立了干燥环境下含SAP水泥基材料固相组成随养护时间的演变模型,这可为热力学模型计算及高原干燥环境下混凝土配合比设计提供数据支持。