Effect of Nano Silica on Porosity and Micromechanical Properties of Hardened Cement Paste
In order to study the effect of different Nano SiO2 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 SiO2 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 SiO2 is 4%,the porosity of cement samples is higher than that of other samples doped with Nano SiO2.Compared with the content of Nano SiO2 is 3%,there are more unhydrated product phases when the content of Nano SiO2 is 4%.Nano SiO2 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.
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