羟乙基甲基纤维素对硫铝酸盐水泥早期水化的影响

Influence of Hydroxyethyl Methyl Cellulose on Early Hydration of Calcium Sulfoaluminate Cement

采用超声/电声谱仪、低场核磁共振仪、量热仪研究了羟乙基甲基纤维素(HEMC)对硅酸盐水泥和快硬硫铝酸盐水泥(CSA)早期水化的影响。测试了砂浆的保水性、含气量等宏观性能。结果表明:HEMC均显著提高了新拌砂浆的保水性和含气量,但对水泥浆体ζ电位的影响截然不同——HEMC的掺入大幅缩短了硅酸盐水泥浆体ζ电位变正的时间,却仅使快硬CSA浆体ζ电位的绝对值略微减小。此外,HEMC掺入后,水泥浆体横向弛豫时间分布曲线在100~1000 ms内出现新的弛豫峰。对硅酸盐水泥水化而言,3 d后此峰基本消失;而快硬CSA浆体120 min时此峰便已消失,表明HEMC在快硬CSA颗粒表面的吸附作用弱,因此不同于HEMC对硅酸盐水泥水化反应显著的延缓作用,HEMC几乎不影响快硬CSA早期水化放热。

The influence of hydroxyethyl methyl cellulose(HEMC)on the early hydration of Portland cement and rapid-hardening calcium sulfoaluminate cement(CSA)was investigated by acoustic and electroacoustic spectrometer and low-field NMR instrument.The water retention and air void content of fresh mortars were analyzed.The results show that regardless of cement variation,the water retention and air void content are improved after the addition of HEMC.The change of zeta potential is related to cement type.For the Portland cement paste,the addition of HEMC greatly shortens the time of zeta potential becoming electropositive,and the absolute value ofζpotential for rapid-hardening CSA paste decreases slightly.In addition,the T2 distribution of HEMC containing cement pastes also appears a relaxation peak at 100–1000 ms.Such a peak disappears after 3-d hydration for the Portland cement,while it only disappears in 120 min for rapid-hardening CSA,indicating that HEMC exerts a weak adsorption on the surface of rapid-hardening CSA particles.Unlike the retardation effect of HEMC on the Portland cement hydration,HEMC hardly affects the early hydration heat release of rapid-hardening CSA.