聚合物-水泥基注浆材料早期流变及水化特性

为制备满足复杂地层加固工程需求的高性能水泥基注浆材料,探究以偏铝酸钠(SA)、聚羧酸(Sp)及高吸水性树脂(SAP)为组分的聚合物体系及其掺量对新拌水泥浆体流变特性与泌水率的影响,并采用水化放热监测与倒置荧光显微技术,对不同体系下水泥浆体早期水化进程及微米级颗粒的悬浮分散形态进行分析.结果表明:新拌水泥浆液流动性和泌水率与SA、SAP掺量呈负相关,随Sp掺量增加而提高. Sp及SAP延缓了水泥早期水化进程,改性样延迟近1 h进入水化诱导期,诱导期内水化放热速率显著降低.在不同掺量SA的促凝效应、Sp的分散效应以及SAP的"水库"作用下,新拌水泥浆液表现为初始及经时流动度大于200 mm的高流态期可分别被控制在10、20、30 min内且析水率小于5%(稳定性浆液),接近临界期时流动度陡降、流变参数突增并迅速凝结的流变特性.结合微观结构观测结果,建立了新拌水泥浆体流变演化模型,揭示多聚合物协调效应下水泥浆体呈现分散-储水-流变-水化的早期流变机制.

Rheological and hydration properties of polymer-cementitious grouting material at early stage

To develop a high performance cement-based grouting materials and use it in complex stratum, the effects of sodium aluminate (SA), superplasticizer (Sp), super-absorbent polymer (SAP) and their dosage on rheological properties and bleeding of fresh cement paste were investigated. The hydration evolution of cement paste at early stage and suspension morphology of particles in different polymers system were also analyzed by heat monitoring and fluorescent inverted microscope. Results indicated that the flowability and bleeding of fresh cement paste negatively related to the dosage of SA and SAP, which were enhanced with the increase of Sp contents. The stage of hydration induction was delayed for about 1 h, then the rate of heat flow decreased significantly with the incorporation of Sp and SAP. Affected by the procoagulant of SA, the dispersion of Sp, and reservoir function of SAP, the period with high flowability (greater than 200 mm) of fresh cement paste could be controlled within 10 min, 20 min, and 30 min respectively with a bleeding ratio lower than 5% (stable slurry). Then the rheological parameters suddenly increased while the fluidity sharply decreased. Combined with microstructure test results, the evolution model was established to reveal the rheological mechanism of dispersion-absorption-rheological-hydration at early stage affected by the synergetic effects of polymers system.