材料期刊网

使用不同配合比的混凝土试件及颗粒标准养护28 d后,浸泡在超纯水和5％的 NaCl 溶液中,采用表面渗透性测试仪(Autoclam)和氮气吸附法定期检测混凝土的表层渗水系数及微观孔结构,研究氯离子对混凝土表层渗水性能及水泥水化浆体微观结构的影响.结果表明,NaCl溶液浸泡会显著提高混凝土表层的抗渗能力,对PC1混凝土,浸泡90 d后,表层渗水系数为超纯水浸泡试件的0．91,150 d后仅为超纯水试件的0．76；氯离子浸入混凝土后,会使混凝土的孔结构细化,显著降低100 nm以下的小孔,实验中,PC1混凝土在NaCl溶液浸泡后,小于100 nm 的孔与超纯水浸泡相比减少了32．43％；PC2混凝土在 NaCl 溶液浸泡后,小于100 nm的孔相比减少了57．24％；NaCl 溶液浸泡下,水泥水化良好,结构较致密,氯离子对水泥浆体的水化过程有一定的促进作用.

In this study,the influences of different immersion conditions on the pore structure and surface layer sorptivity were investigated.After cured for 28 d under standard conditions,concrete specimens with different mix proportions were immersed in ultrapure water and 5% NaCl solution,and Autoclam (a surface sorptivity tester)was used to measure the evolution of surface sorptivity of the concrete specimens following time.In par-allel,paste particles taken from the specimens were cured and immersed under the same conditions,and used for pore structure characterization.It was found that immersion in NaCl solution could significantly improve the surface water-absorption resistance of concrete as compared with the ultrapure water immersion.For example, for concrete PC1,at the immersion age of 90 d,the surface water-sorptivity of concrete immersed in NaCl solu-tion was 0.91 of the specimen immersed in ultrapure water,while this factor decreased to 0.76 at the immersion age of 150 d.This influence could be attributed to the fact that the penetration of chloride ions into concrete made the pore structure finer,and reduced the volume fraction of pores under 100 nm.It was found in experi-ments that for PC1,the volume of pores under 100 nm in specimens under NaCl solution immersion was 32.42% lower than that under ultrapure water immersion,and this ratio was 57.24% for PC2.It was proved that chloride ions facilitated the hydration of cement,thus the immersion in NaCl solution helped cement paste in concrete achieving better hydration and denser microstructure.