采用XRD、29Si和27Al NMR等测试手段,研究了聚环氧琥珀酸对水泥浆体铝离子配位结构的影响机理.结果表明,聚环氧琥珀酸能阻止硅酸盐矿物水化,抑制掺杂在Alite和Belite矿中的四配位铝(Al[4])参与水化,不利于铝氧四面体进入到C-S-H结构取代硅氧四面体,促使浆体中Al[4]向六配位铝(Al[6])转化.聚环氧琥珀酸掺量存在一个最佳值,掺量较小时,聚环氧琥珀酸与水泥浆体中Ca2+键合后带正电荷,极易与SO42-结合形成螯合物,促使AFt、AFm中Al[6]向TAH(Third aluminum hydrate)中Al[6]转化,达到抑制AFt、AFm结晶的作用;当掺量较大时,聚环氧琥珀酸通过Ca2+桥连另外的聚环氧琥珀酸形成环状结构,降低了聚环氧琥珀酸固化SO42-的程度,进而使大量TAH中Al[6]逐步向AFm、AFt中Al[6]转化,反而促进了AFt结晶形成.
The machanism of polyepoxysuccinic acid on coordination structure of aluminum ions in Portland cement pastes was investigated by XRD, 29Si and 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR).The results indicate that the polyepoxysuccinic acid can prevent hydration of silicate minerals, and can inhibit the hydration of tetrahedral coordination Al3+ (Al[4]) incorporated in Alite and Belite, and then it is not advantageous to Al-O tetrahedral substituting for Si-O tetrahedral in the structure of C-S-H, impeling the Al[4] transformed into the six-coordination Al3+ (Al[6]).Moreover, there is the optimum mix amount for the polyepoxysuccinic acid in cement pastes.When the mixing amount is less, the Ca2+ ions in cement pastes will be bonded by the polyepoxysuccinic acid, leading to generation of positive charge, and then it very easily combines the SO42-ions forming the chelates, impeling the transfromation of the Al[6] in AFt or AFm into the Al[6] in TAH (Third aluminum hydrate), finally, it will achieve the inhibitory action on the crystallization of AFm and AFt.However, when the mixing amount is more, the polyepoxysuccinic acid will be bridged with other polyepoxysuccinic acid, by means of the cross-linkage of Ca2+ ions, forming into the cycle-type structure.And then, it will lead to the reduction of the polyepoxysuccinic acid solidifying SO42-ions, making the transformation of a amount of Al[6] in TAH into the Al[6] in AFm and AFt, on the contrary, the crystallization of AFt will be promoted by the excess polyepoxysuccinic acid.
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