质子核磁共振技术研究水泥早期水化过程

Research on Hydration of Cement at Early Age by Proton NMR

用低场质子核磁共振技术研究了新拌水泥浆体中水的纵向弛豫时间T1的初始分布、加权平均值和总信号量随水化时间的变化及其与早期水化过程的关系.结果表明:初始水化时,T1分布呈2个峰,其中主峰代表填充在水泥颗粒间的水,而次峰表示絮凝结构中的水;T1加权平均值随水化时间的增长呈下降趋势,且其变化趋势与水化过程具有良好的相关性,可以依次划分为初始期、诱导期、加速期和稳定期这4个阶段;T1的弛豫信号总量对应于浆体中的物理结合水量,其相对量随水化时间不断降低,反映了水化反应中物理结合水转变为化学结合水的过程.

Changes of initial distribution,weighted mean values and total signal intensity of longitudinal relaxation time（T_1） of water in fresh cement pastes as a function of hydration time and its correlation with hydration process during the early age was studied with low field proton nuclear magnetic resonance（NMR）.T_1 distribution curves at initial time exhibit two peaks.The main peak is related to water filling in space around the cement grains while the minor one represents the water constrained in flocculations.The evolution curves of weighted mean values of T_1 are in good agreement with the hydration process of cement pastes and could be roughly divided into four stages： initial period,dormant period,accelerated period and steady period.The total signal intensity detected in experiments is proportional to the amount of physically bound water in the pastes.Since the transition from physically to chemically bound water,the relative percentage decreases as the hydration time increases.