基于低场核磁技术研究混凝土标准养护过程微结构水分演化规律

Research on Microstructure Water Evolution Law of Standard Curing Process of Concrete Based on Low-Field Nuclear Magnetic Technology

摘要: 快速准确地评价混凝土养护质量对混凝土的研究具有重要意义。本文采用低场核磁技术研究了大尺寸混凝土试件在标准养护过程中含水量的演变规律，测试的龄期分别为1 d、3 d、7 d、14 d、28 d和56 d，同时建立了与同批次试件的强度的关系。结果表明：随着养护龄期的增加，混凝土水含量不断降低。混凝土在养护过程中内部水的弛豫时间演化规律主要有三类特征。其中，养护期内弛豫时间为0.01~10 ms的孔隙水不断减少，水分降低速率减小；养护期内弛豫时间为10~100 ms的孔隙水持续降低，但14 d后孔隙水不再改变；养护期内弛豫时间为大于100 ms的孔隙水，在养护期内未发生变化，这种弛豫时间的差异说明了不同尺度的混凝土孔隙水化过程的变化特征。相对孔隙水含量与混凝土强度的相关系数R²为0.9938，可为评价混凝土养护质量提供试验依据，能准确高效地评价混凝土的质量。

Abstract: The rapid and accurate assessment of concrete curing quality is of great significance for concrete research. In this study, low-field nuclear magnetic technology was employed to investigate the evolution law of moisture content in large-sized concrete specimens during the standard curing process. The tested age periods were 1 day, 3 days, 7 days, 14 days, 28 days, and 56 days, and a correlation with the strength of specimens from the same batch was simultaneously established. The results indicate that as the curing period increases, the moisture content of concrete continuously decreases. The evolution law of relaxation times of internal water in concrete during the curing process exhibits three main characteristics. Among them, the pore water with relaxation times of 0.01~10 ms continuously decreases, and the rate of moisture reduction decreases. The pore water with relaxation times of 10~100 ms continues to decrease, but after 14 days, it no longer changes. The pore water with relaxation times exceeding 100 ms shows no changes during the curing period, and this difference in relaxation time illustrates the changing characteristics of the pore hydration process in concrete at different scales. The correlation coefficient (R²) between the relative pore water content and concrete strength is 0.9938, providing a basis for evaluating the quality of concrete curing and enabling an accurate and efficient assessment of concrete quality.