无石膏条件下含镁C3A早期水化特征

Early hydration characteristics of magnesium-doped C3A in the absence of gypsum

摘要:

为探索无石膏条件下含镁C3A早期水化特征，煅烧制备了掺加16.67%和28.57%MgO的C3A样品，并分析了样品水化过程中的物相组成演化规律和水化程度。结果表明：MgO显著促进了C3A的水化，水化1h后即生成镁铝双金属氢氧化物（Mg-Al layered double hydroxides，Mg-Al LDH），且Mg-Al LDH含量随样品中的MgO含量增加而显著提升。掺加28.57%MgO的样品水化3d的C3A水化程度达到95%，较掺加16.67%MgO的样品提高20%~30%。Mg-Al LDH的形成过程中未发现明显的Mg(OH)2相，表明Mg-Al LDH的形成并非通过Mg(OH)2中间产物，而是由MgO直接水解产生的Mg2+和C3A水解释放的Al3+在碱性条件下形成，因此Mg-Al LDH的形成也加速了MgO的水解。

Abstract:

To investigate the early hydration characteristics of magnesium-doped C3A in the absence of gypsum, C3A samples incorporating 16.17% and 28.57% MgO were prepared by calcination, and the evolution of phase composition and hydration degree during hydration were analyzed. The results demonstrate that MgO significantly promotes the hydration of C3A, with magnesium-aluminum layered double hydroxides (Mg-Al LDH) forming within 1 h of hydration. The content of Mg-Al LDH increases markedly with higher MgO incorporation in the samples. The sample with 28.57% MgO achieves a C3A hydration degree of 95% after 3 days, representing a 20%-30% improvement compared to the sample with 16.67% MgO. No distinct Mg(OH)2 phase is observed during the formation process of Mg-Al LDH, indicating that Mg-Al LDH forms not through an intermediate Mg(OH)2 product but rather through direct reaction between Mg2+ (from MgO hydrolysis) and Al3+ (released from C3A hydration) under alkaline conditions. Consequently, the formation of Mg-Al LDH also accelerates the hydrolysis of MgO.