基于低场核磁共振技术的水泥浆体凝结时间及早期强度分析

Analysis of Setting Time and Early Strength of Cement Paste by Low Field Nuclear Magnetic Resonance

采用低场核磁共振技术,研究了不同水灰比条件下水泥浆体早期水化过程中可蒸发水含量的变化.结果表明:可蒸发水核磁信号量随时间变化的一阶微分曲线与水泥浆体早期水化的5个阶段吻合较好;水泥浆体初、终凝时间介于核磁信号量一阶微分曲线的谷、峰之间,即初凝出现在水化加速期开始之后,终凝出现在加速期结束之前.通过对核磁信号量的计算分析可以获得水泥浆体的水化程度和胶空比,硬化水泥浆体的实测抗压强度与计算所得胶空比呈幂函数关系.

The change of the content of evaporable water in the early hydration process of cement paste with different water-cement ratios was studied by low field nuclear magnetic resonance(NMR).The results show that the first-order derivative of signal intensity of the cement paste fits well with the five stages of the early hydration of the paste.The initial and final setting time of cement paste are between the valley and peak of the first-order derivative curve of NMR signal intensity,which means the initial set appears after the beginning of the acceleration stage,and the final set appears before the end of the acceleration stage.Hydration degree and gel-space ratio are calculated by signal intensity.The calculated gel-space ratio fits well with the measured compressive strength of hardened cement paste through a power function.