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研究采用电阻率法,深入揭示和阐释了早龄期混凝土微观结构由于其凝胶特性所导致的独特的演变规律。考虑到混凝土中凝胶孔的可连通性,建立了适用于表征混凝土电阻率和微观特征参数相关关系的修正阿尔奇公式,并基于此研究阐释了混凝土早龄期有效孔隙率φ_(eff)迂曲度a的演变规律。以电阻率变化率曲线上的P_2点为分界点,将混凝土早龄期微观特征演变过程划分为有效孔隙率φ_(eff)空制和迂曲度a控制两个阶段。其中,迂曲度a控制阶段的产生是由于主要水化产物C-S-H凝胶形成过程中密实度和内聚力不断增加的结果。这也揭示了胶凝体的凝胶特性在混凝土微观结构演变过程中的决定性作用。迂曲度开始上升关键点发生的时刻标志着由凝胶体内部密实过程占主导地位的微观特征演变第二阶段的到来。在1 d龄期之后,C-S-H凝胶的内部密实将逐步取代孔隙率下降因素而成为混凝土力学性能增长的主要微观根源。
In this study, the resistivity method was used to reveal and explain the unique evolution rule of early age concrete microstructure due to its gel properties. Taking account of the connectivity of gel pores in concrete, a modified Archie formula suitable for characterizing the correlation between concrete resistivity and microscopic characteristic parameters was established. Based on this, the effective porosity φ eff (efflux) of concrete in early age was explained Degree of evolution of a law. Taking the P 2 point on the rate of change of resistivity curve as the cut-off point, the microscopic evolution of the early age of concrete is divided into two phases: the effective porosity φ eff and the tortuosity a control. Among them, the tortuosity a control phase was produced as a result of the increasing compactness and cohesion during the formation of the C-S-H gel, the major hydration product. This also reveals the decisive role of gel properties of gels in the evolution of concrete microstructures. The moment when tortuosity began to rise marked the second phase of the evolution of microscopic features dominated by dense processes within the gel. After 1 day, the internal compactness of C-S-H gel will gradually replace the porosity reduction factor and become the main microscopic source for the increase of mechanical properties of concrete.