Effect Of Nano-silica Sol Dosage On Mechanical Properties And Microstructure And Durability Of Cement-based Material

This paper mainly studied the influence of different pH values silica sol on themechanical properties of the cement mortar; analysized the function mechanism ofacidic,neutral and alkaline silica sol; analysized the effect of different kinds of silanecoupling agent and surface-active agent on the stability of the modified silica sol; testedthe percent grafting and the water-blocking of the modified silica sol under thecondition of the pH, synthesis temperature, synthetic time and the mixing amount of thesilane coupling agent and so on; compared the anti-carbonate, the resistance of sulfateattacks and the frost resistance of cement mortar mixed by alkaline silica sol andbrushed with the modified silica sol. The experimental results show that:(1) In the colloidal silica nanometer SiO2has high pozzolanic activity, can react withthe hydration products of Ca(OH)2to form C-S-H gel. Compared with A25and N25PA30of nano silicon dioxide can better disperse in water slurry, the hydration productsfill the gaps, SEM observation of hardened cement paste structure integration, and inmixed A25and N25of hardened cement paste were aggregate, make the improvementin microstructure of mixed PA30mortar test block of mechanical properties areimproved greatly.(2) Through the study on the stability of modified silica sol, it is concluded that theshort chain silane coupling agent and low molecular weight alcohols surfactant canmake the modified the existence of the solution is more stable; By silane coupling agentand net pulp bibulous rate, get a short chain of silane coupling agent modified inorganicsilicon sol the best synthesis process for: MSiO2: Mcoupling agent=3:1; pH=2;The synthesistemperature of40℃. Synthetic time for40min. MTMS hydrophobic effect of modified silica sol significantly because of MTES, the higher the stability of the solution and theinfrared spectrum analysis of the grafting mechanism of silane coupling agent.(3) Based on the research of the mortar thickness, dipping time, get the modifiedsilica sol coating amount to0.21~0.22Kg/m2constant value, studies the alkaline silicasol coating outside and inside outside mixing, besmear respectively modified silica solstudies the influences on the mechanical behavior of cement mortar, the results showthat the coating way outside of the28d compressive strength of cement mortar, hascertain influence on flexural strength of28d; In mixing modified silica sol cansignificantly reduce the early compressive strength of cement slurry net, can prolong thesetting time of cement.(4) Mixed PA30inside and outside coating modification A25two ways of cementmortar block can reduce the carbonation depth and improve the performance ofcarbonation resistance of cement mortar; Can significantly reduce the strength losscaused by the freeze-thaw cycle and quality loss; Improve the block sulfate resistance ofmortar. Compared with the mixing, besmear outside can make active nano-silicondioxide in block surface concentration, unmodified active nano-silicon dioxide fillingeffect of secondary hydration, the partition of the hydrophobic effect of compositecoating, the coating effect makes the outside sand coated silica sol gel block can betterwithstand erosion medium into, so as to make the cement mortar block with higherperformance of carbonation resistance, frost resistance and sulfate attack resistance.