稻壳灰掺量对修补砂浆流变性能及力学性能的影响规律及机理分析

Effect of Rice Husk Ash Content on Rheological and Mechanical Properties of Repaired Mortar and Its Mechanism Analysis

采用600℃烧制的稻壳灰(RHA)制备了基于RHA的修补砂浆,研究了不同掺量下稻壳灰对修补砂浆力学性能和流变性能的影响,同时结合水化热、水化产物、微观形貌、孔隙结构等分析稻壳灰对水泥水化的影响及其对砂浆强度的增强机理。结果表明:随着RHA掺量的增加,修补砂浆的流动度不断降低,但修补砂浆的屈服应力和塑性黏度增大,RHA的掺入并未改变水泥浆体的流变类型。RHA的掺入降低了修补砂浆早期的力学性能,但明显提升了修补砂浆的中后期强度,当RHA掺量为6%时,修补砂浆28 d力学性能达到最好。收缩性能研究表明,当RHA掺量为10%时,水泥砂浆的干燥收缩值最小。RHA对水泥早期(<1d)的水化过程有抑制作用,但是对后期(>1d)的水化过程具有一定的促进作用,且随着RHA掺量越高,水泥水化速率逐渐加快。RHA中高活性的SiO_(2)促进水泥水化的同时也参与水泥的二次水化反应,生成大量的C⁃S⁃H凝胶和钙矾石,C⁃S⁃H凝胶将内部串联成一个整体,使得水泥砂浆内部的物质能更好地连接在一起,从而提高修补砂浆的强度。

Rice husk ash(RHA)fired at 600℃was used to prepare a repair mortar based on RHA.The effects of rice husk ash on the mechanical properties and rheological properties of the repair mortar at different dosages were studied.Meanwhile,the effects of rice husk ash on cement hydration and the strengthening mechanism of mortar strength were analyzed in combination with hydration heat,hydration products,micromorphology and pore structure.The results show that the fluidity of repaired mortar decreases with the increase of RHA content,but the addition of RHA does not change the rheological type of cement slurry,and the yield stress and plastic viscosity of repaired mortar increase with the increase of RHA content.The addition of RHA decreased the mechanical properties of the repaired mortar in the early stage,but significantly improved the strength of the repaired mortar in the middle and late stages.When the RHA content was 6%,the mechanical properties of the repaired mortar reached the best at 28 d.The shrinkage performance study shows that when the RHA content is 10%,the dry shrinkage value of cement mortar is the smallest.RHA can inhibit the hydration process of cement in the early stage(<1d),but can promote the hydration process in the later stage(>1d)to a certain extent,and the hydration rate of cement gradually increases with the increase of RHA content.The highly active SiO_(2) in RHA not only promotes the hydration of cement,but also participates in the secondary hydration reaction of cement,generating a large amount of C⁃S⁃H gel and ettringite.C⁃S⁃H gel connects the interior of cement mortar into a whole,so that the substances inside cement mortar can be better connected together,thus improving the strength of repair mortar.