Huang Jingjing, Wang Zhongkun, Li Dongsheng, Li Gengying
Department of Civil Engineering, Shantou University, Shantou 515063, China.
College of Civil Engineering and Architecture, Wenzhou University, Wenzhou 325035, China.
Nanomaterials (Basel). 2022 Jan 19;12(3):323. doi: 10.3390/nano12030323.
Sulfate resistance of high-volume fly ash/cement mortars hybrid containing 01.5 wt.% of nano-silica (Nano-SiO, NS) and 01.0 vol.% of polyvinyl alcohol (PVA) fibers was investigated in this study. Fly ash was replaced with Portland cement at levels of 60% by weight. The resistance to sulfate attack was investigated by exposing the mortars to 10 wt.% sodium sulfate (NaSO) solutions for 72 days, after which change in mass, compressive, and flexural strengths were determined. For comparison, the compressive and flexural strengths of cement mortar after 100 days of curing in water were also investigated. Microstructural deteriorations caused by sulfate attack were analyzed by using scanning electron microscope (SEM). The test results showed that the combination of NS and PVA fibers was effective in enhancing the mechanical properties and the resistance to sulfate attack. After 28 days curing, the hybrid addition of 1.5 wt.% NS and 1.0 vol.% PVA fibers increased the flexural strength by 90% over the control one without NS and PVA fiber. Moreover, regardless of PVA fibers content, due to the crystal nucleus and pore-filling effects, the adding of 0.5 wt.% NS increased the compressive strength by 67.1118.2%. Chemical reaction took place between fly ash and NaSO as no un-hydration particles could be observed in the samples immersed in NaSO solutions for 72 days, while a lot of un-hydration fly ash particles could be found in the SEM image of mortar after 100 days curing in water. The chemical reaction production could increase the adhesive property and fill the pores of cement mortar. As a result, the compressive and flexural strengths of cement mortars after immersed in NaSO solution for 72 days, were much higher than that after 28 days curing. Moreover, the compressive strength of mortars incorporating 1.01.5 wt.% NS was even higher than that after 100 days curing in water, indicating the combination of Nano-SiO/PVA fiber is effective in enhancing the resistance to sulfate attack.
本研究对含有01.5 wt.%纳米二氧化硅（Nano-SiO₂，NS）和01.0 vol.%聚乙烯醇（PVA）纤维的大掺量粉煤灰/水泥砂浆复合材料的抗硫酸盐性能进行了研究。粉煤灰以60%的重量取代了波特兰水泥。通过将砂浆暴露于10 wt.%的硫酸钠（Na₂SO₄）溶液中72天来研究其抗硫酸盐侵蚀性能，之后测定质量、抗压强度和抗折强度的变化。作为对比，还研究了水泥砂浆在水中养护100天后的抗压强度和抗折强度。利用扫描电子显微镜（SEM）分析了硫酸盐侵蚀引起的微观结构劣化。试验结果表明，NS和PVA纤维的组合有效地提高了力学性能和抗硫酸盐侵蚀性能。养护28天后，1.5 wt.% NS和1.0 vol.% PVA纤维的混合添加使抗折强度比不含NS和PVA纤维的对照样提高了90%。此外，无论PVA纤维含量如何，由于晶核和孔隙填充作用，添加0.5 wt.% NS使抗压强度提高了67.1%118.2%。粉煤灰与Na₂SO₄之间发生了化学反应，因为在浸泡于Na₂SO₄溶液72天的样品中未观察到未水化颗粒，而在水中养护100天后的砂浆SEM图像中可以发现大量未水化的粉煤灰颗粒。化学反应产物可以提高粘结性能并填充水泥砂浆的孔隙。结果，浸泡在Na₂SO₄溶液72天后的水泥砂浆的抗压强度和抗折强度远高于养护28天后的强度。此外，掺入1.01.5 wt.% NS的砂浆的抗压强度甚至高于在水中养护100天后的强度，表明纳米SiO₂/PVA纤维的组合有效地提高了抗硫酸盐侵蚀性能。
