矿物掺合料对水泥孔溶液碱度和强度影响及机理研究

对比研究了粉煤灰、矿粉等矿物掺合料种类、掺量,对不同养护龄期复合水泥浆体孔溶液碱度和强度的影响规律,通过扫描电镜(SEM)、X射线衍射(XRD)、热重(TG)等技术手段对不同养护龄期硬化水泥浆体水化产物成分及微观形貌进行了表征并揭示其作用机理。结果表明:矿物掺合料的掺入降低了复合水泥浆体的碱度系数,随着掺量的增加其碱度持续降低,28d碱度系数在12.2左右,比纯水泥降低了0.8左右,且强度未出现明显降低。相同掺量时,粉煤灰水泥复合体系孔溶液碱度低于矿粉水泥复合体系。原因在于粉煤灰和矿粉的掺入降低了复合水泥浆体Ca(OH)2的生成量,养护28d分别降低54%和32%,并且生成了部分低钙硅比的C—S—H凝胶水化产物。

Effect of Mineral Admixtures on Alkalinity and Strength of Cement Pore Solution and Its Mechanism

Abstract:The effects of different amounts of fly ash and slag powder on the alkalinity coefficient and strength of composite cement slurry pore solution were studied,The hydration products of hardened cement pastes at different ages were micro-characterized and the mechanism was revealed by means of TG, XRD, and SEM.The results show that the incorporation of mineral admixtures reduces the alkalinity coefficient of the composite cement slurry.With the increase of the dosage, the alkalinity continued to decrease, and the 28d alkalinity coefficient was about 12.2, which was 0.8 lower than that of the pure cement system, and the strength did not decrease significantly.At the same dosage, the alkalinity of pore solution of fly ash cement composite system is lower than that of slag cement composite system.The reason is that the incorporation of fly ash and mineral powder reduces the amount of Ca(OH)2 produced in the composite cement slurry, which reduces 54% and 32% respectively after 28 days of curing, and generates a part of the C-S-H gel hydration with low Ca/Si product.