共混乳液改性水泥砂浆的氯离子扩散系数

Chloride Diffusion Coefficient of Latex Blend Modified Mortars

研究了共混乳液组成及其薄膜的力学性能与共混乳液改性水泥砂浆氯离子扩散系数的关系.试验结果发现,少量氯偏乳液与丁苯胶乳共混,可以显著降低改性砂浆的氯离子扩散系数,丙苯乳液与丁苯胶乳共混,当质量比为3∶2～4∶1时,砂浆的氯离子扩散系数较低.聚合物乳液改性砂浆的氯离子扩散性与聚合物本身的拉伸强度和断裂伸长率有关.聚合物本身的拉伸强度越低、断裂伸长率越大,则改性砂浆的氯离子扩散系数越小.当共混乳液薄膜的断裂伸长率从200%～300%增大到800%以上时,相应改性砂浆的氯离子扩散系数由(10～15)×10-12m2/s降低到(3～4)×10-12m2/s.

The chloride diffusivity of latex blend modified mortars and its dependence on the mechanical property of film formed from latex blend were studied. The test results show that the chloride diffusivity of latex blend modified mortars can be improved with latex blend with suitable compositions. In the range of this study, the blend of vinyl chloridevinylidene chloride copolymer emulsion (PVDC) and styrenebutadiene rubber latex (SBR) with minor mass fraction of PVDC can significantly reduce the chloride diffusivity of latex blend modified mortars. The best effect is achieved with the blends of styreneacrylate copolymer emulsion (SAE) and SBR with mass fraction between 3∶2 and 4∶1. Chloride diffusivity of latex blend modified mortars can be well related to the tensile strength and elongation at break of the latex blend films. The chloride diffusion coefficient of the modified mortars increases approximately linearly with the tensile strength of the latex blend films, and decreases with the increase of the elongation at break of the latex blend films. If the elongation at break of the latex blend films increases from 200%～300% to more than 800%, the chloride diffusion coefficient of the modified mortars decreases from (10～15)×10-12 m2/s to (3～4)×10-12 m2/s.