聚羧酸减水剂对水泥浆体早期单碳铝酸钙形成的影响

利用傅里叶红外光谱（FTIR）、扫描电子显微镜（SEM）、热重分析（DTG）和等温吸附,研究了含石灰石填料（LF）水泥在掺用聚羧酸减水剂（PCA）时,硬化浆体中单碳型水化碳铝酸钙（AFmc）的形成规律.研究发现,水泥在水化15min的初始期就形成了AFmc,PCA通过促进早期C4AF水化使含铁的AFmc更易形成.以萘磺酸盐缩合物减水剂取代PCA时,未观察到相同现象.由于浆体中AFmc和钙矾石（AFt）的共存,减少了水泥矿物对PCA的吸附量,从而改善了PCA与水泥的适应性.因此,当混凝土中掺用LF时,PCA应作为首选的高效减水剂.

Early calcium monocarboaluminate hydrate formation in cement paste: effect of polycarboxylate type admixture

Effects of polycarboxylate type admixture（PCA）on calcium monocarboaluminate hydrate（AFmc）formation in hydrated cement paste containing limestone filler（LF）are investigated by the Fourier transform infrared spectroscopy（FTIR）,the scanning electron microscopy（SEM）,the derivative thermogravimetric（DTG）analysis and the adsorption amount measurement.Experimental results indicate that AFmc forms during the initial hydration period of cement as early as 15 min.It is found that PCA accelerates the early age AFmc formation and enhances cement hydration by promoting C4AF hydration at the early age,and,as a consequence,the iron associated AFmc phase forms more readily.The phenomenon is not observed when PCA is replaced by a naphthalene formaldehyde sulphonate condensate water reducer.Compatibility between PCA and cement is modified due to the presence of AFmc along with ettringite（AFt）,which results in a less adsorption amount of PCA on the surface of cement minerals.As a kind of high-range water reducer,PCA may be the preferred choice for concrete containing LF.