多外加剂对硬化水泥浆体强度及水化特征的影响

Influence of Chemical Admixture Systems on Strength and Hydration Characteristics of Hardened Cement Paste

关键词:  外加剂  强度发展  水化放热速率  孔径分布  微观结构

Key words:  admixture  strength development  hydration heat rate  pore distribution  microstructure

摘要:

从微观孔结构角度探究以偏铝酸钠(SA)速凝剂、聚羧酸减水剂(Sp)、高吸水性树脂(SAP)保水剂为组分的外加剂体系对硬化水泥浆体强度及水化特征的影响机理，揭示其宏观性能与微观结构间的本质关联.结果表明：SA的溶解沉淀、Sp的分散效应以及SAP的“水库”作用分别提高了水泥的早期水化速率、后期水化面积与水化程度；水泥水化加速期内最大放热峰峰值显著提高；28d龄期时改性水泥浆体抗压强度较7d时增长78%，多外加剂的协调效应改善了因单掺速凝剂所导致的水泥基注浆材料后期力学性能发展缓慢的缺陷；复合掺用SA，Sp及适量SAP可显著降低水泥浆体孔径尺寸，使其孔径分布趋于细化；SAP存在阈值掺量，其释水后大尺寸空孔的堆积导致水泥浆体孔结构及力学性能劣化；28d龄期时各体系平均孔径差异与强度试验结果一致，孔径分布规律可有效反映硬化水泥浆体力学性能的变化特征.

Abstract:

The effects of sodium aluminate(SA), superplasticizer(Sp) and super absorbent polymer(SAP) on strength and hydration characteristics of hardened cement paste from the view of pore structure were investigated to reveal the correlation between microstructure of hardened cement paste and their macroscopic properties. The results show that the maximum exothermic peak is significantly enhanced in acceleration period of cement hydration. Depending on dissolution precipitation of SA, dispersion of Sp and function of SAP as reservoir, the hydration rate in early ages, hydration area and hydration degree in late ages are improved. The compressive strength of modified cement paste at 28d reaches 178 times higher than that of 7d, which reveals that the late mechanical properties of cement based grouting materials with accelerator can be improved by the moderating effect of admixtures. While the threshold dosage of SAP after releasing water leads to degradation of pore structure and mechanical properties. Uniformity of average pore radius for different admixture systems and their compressive strength at 28d show that the characteristics of mechanical properties can be reflected efficiently by the pore size distribution.