纳米SiO_(2)对水泥浆体孔隙和微观力学性能的影响

Effect of Nano Silica on Porosity and Micromechanical Properties of Hardened Cement Paste

为了研究不同纳米SiO_(2)掺量对硬化水泥浆体孔隙率与微观力学性能的影响,采用压汞实验,纳米压痕测试与GMM法获得了水泥浆体的孔隙率,压痕模量,硬度与各水化产物相的分布,并使用XRD与SEM表征了各性能最优样品的表面形貌与内部产物。试验结果表明,养护龄期为28天时,与空白对照组相比,当纳米SiO_(2)的掺量质量分数为1%、2%和3%、4%时,水泥样品总孔隙率分别降低了14.07%,16.67%,26.83%和7.43%,LD C-S-H与HD C-S-H的含量之和分别为对照组的99.34%,101.34%,117.48%和113.33%。但当纳米SiO_(2)的掺量质量分数为4%时,水泥样品的孔隙率比其他掺纳米SiO_(2)的样品更高,且与纳米SiO_(2)掺量质量分数为3%时相比,未水化的产物相也较多。纳米SiO_(2)可以充分发挥成核效应和火山灰效应,生成更多的C-S-H并改变硬化水泥浆体的微观形貌,从而有效降低水泥浆体的孔隙率并提高其微观力学性能。

In order to study the effect of different Nano SiO_(2) content on the porosity and micromechanical properties of hardened cement paste,the porosity,indentation modulus,hardness and phase distribution of each product of cement paste were obtained by mercury intrusion test,nano indentation test and GMM method,and the sample morphology and hydration products with the best performance were characterized by XRD and SEM.The test results show that when the curing age is 28 days,compared with the blank control group,when the content of Nano SiO_(2) is 1%,2%,3%and 4%,the total porosity of the cement sample decreases by 14.07%,16.67%,26.83%and 7.43%respectively,the sum of LD C-S-H and HD C-S-H was 99.34%,101.34%,117.48%and 113.33%of the control group,respectively.However,when the content of Nano SiO_(2) is 4%,the porosity of cement samples is higher than that of other samples doped with Nano SiO_(2).Compared with the content of Nano SiO_(2) is 3%,there are more unhydrated product phases when the content of Nano SiO_(2) is 4%.Nano SiO_(2) can give full play to the nucleation effect and pozzolanic effect,generate more C-S-H and change the micro morphology of hardened cement paste,so as to effectively reduce the porosity of cement paste and improve its micro mechanical properties.