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利用椭圆环开裂仪、比长仪、等温量热仪、压汞仪(MIP)及扫描电子显微镜(SEM),重点研究了在高碱含量水泥基材料中,K+/Na+摩尔比对其早期开裂敏感性的影响及机制,并探究了粉煤灰对不同K+/Na+摩尔比高碱水泥基材料早期开裂敏感性的影响。结果表明:K+/Na+摩尔比每增加1倍,水泥基材料初始开裂时间缩短3%左右,主要作用机制在于高K+/Na+摩尔比,增加了水泥基材料水化速率和对收缩影响较大的孔径小于50nm的孔分布,导致浆体内部毛细孔水含量降低,孔隙压力增加,早期收缩率增加,收缩应力增大同时水泥基材料抗拉强度和结晶度的下降,降低了水泥基材料基体抵抗拉应力的能力,使水泥基材料开裂敏感性增加;粉煤灰并不能改变水泥基材料早期开裂随K+/Na+摩尔比的增加而增加这种规律,但能有效降低水泥材料开裂敏感性,其作用机制在于粉煤灰延缓了水泥早期水化,在一定程度上降低了孔压力,早期收缩率降低,同时增加了水泥基材料基体抵抗拉应力的能力,使水泥基材料具有良好抵抗早期开裂能力。
The cracking of K + / Na + in cement-based materials with high alkali content was mainly studied by means of oval ring splitter, specific length analyzer, isothermal calorimeter, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) Sensitivity and mechanism of fly ash on the early cracking susceptibility of high-alkali cement-based materials with different K + / Na + molar ratios. The results show that the initial cracking time of cement-based materials is shortened by about 3% every time the molar ratio of K + / Na + is doubled. The main mechanism is the high K + / Na + molar ratio, which increases the hydration rate of cement-based materials and greatly affects the shrinkage Pores with a diameter of less than 50 nm lead to a decrease in water content in the pores of the slurry, an increase in pore pressure, an increase in early shrinkage, an increase in shrinkage stress, and a decrease in tensile strength and crystallinity of the cement-based material, reducing matrix resistance Tensile stress sensitivity of cement-based materials increased cracking; fly ash does not change the early cracking of cement-based materials with the increase of K + / Na + molar ratio of this rule, but can effectively reduce the cracking sensitivity of cement materials, which The mechanism is that fly ash slowed the early hydration of cement, reduced the pore pressure to a certain extent, decreased the early shrinkage rate, and at the same time increased the ability of the cement-based material matrix to resist tensile stress and enabled the cement-based material to have good resistance to early cracking .