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目的:采用碱浸出量定量评价醋酸乙烯/乙烯共聚可再分散(VAE)乳胶粉对硅酸盐水泥基饰面砂浆二次泛白的影响,并分析其作用机理。创新点:采用定量化手段评价硅酸盐水泥基饰面砂浆的二次泛白程度。方法:1.采用碱浸出率方法定量评价硅酸盐水泥基饰面砂浆的二次泛白程度;2.采用水浸取法测试硅酸盐水泥基饰面砂浆内部可溶性Ca2+、K+和Na+的含量,p H值及可溶性物质总含量等;3.以硅酸盐水泥基饰面砂浆毛细孔失水速率表征其内部水的蒸发速率。结论:1.硅酸盐水泥基饰面砂浆的碱浸出量可用于定量评价其二次泛白程度,碱浸出量越大,二次泛白越严重;当碱浸出量大于1 g/(m2·h)时,硅酸盐水泥基饰面砂浆会呈现出可见二次泛白;2.Ca2+,K+和Na+等碱离子是导致硅酸盐水泥基饰面砂浆二次泛白的主要根源;3.VAE乳胶粉增加了硅酸盐水泥基饰面砂浆内部Ca2+,K+和Na+等碱离子的含量,并且促进它们向表面迁移,增加了碱浸出率,从而促进二次泛白。
OBJECTIVE: To quantitatively evaluate the effect of vinyl acetate / ethylene copolymerizable redispersible (VAE) latex powder on secondary whitening of Portland cement-based mortar with alkali leaching, and to analyze its mechanism. Innovative point: Quantitative means to evaluate the degree of secondary whitening of Portland cement-based mortar. The alkali leaching rate was used to quantitatively evaluate the secondary whitening degree of Portland cement-based mortar; 2. The content of soluble Ca2 +, K + and Na + in Portland cement-based surface mortar was tested by water immersion method , p H value and the total content of soluble substances, etc .; 3. The rate of capillary water loss of portland cement-based surface mortar was used to characterize the evaporation rate of water inside. The alkali leaching amount of Portland cement-based surface mortar can be used to quantitatively evaluate the extent of secondary whitening. The greater the amount of alkali leaching, the more severe the secondary whitening. When the amount of alkali leaching is more than 1 g / (m2) · H), visible whitening of Portland cement-based mortar appears secondarily; 2. Alkali ions such as Ca2 +, K + and Na + are the main sources of secondary whitening of Portland cement-based mortar; 3.VAE latex powder increased the content of Ca2 +, K + and Na + in Portland cement-based surface mortar, and promoted the migration to the surface, increased the alkali leaching rate and promoted the second whitening.