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Journal of Zhejiang University SCIENCE A
ISSN 1673-565X(Print), 1862-1775(Online), Monthly
2015 Vol.16 No.2 P.143-150
Influence of vinyl acetate/ethylene copolymer powder on secondary efflorescence in Portland cement-based decorative mortar
Abstract: In this paper, the effect of redispersible vinyl acetate/ethylene copolymer powder (VAE) on the secondary efflorescence of Portland cement-based decorative mortar (PCDM) was evaluated by alkalis leachability. The secondary efflorescence substances were investigated using X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscope (SEM). The mechanism was also analyzed from the aspect of soluble components in PCDM. The results show that the secondary efflorescence level of PCDM can be quantitatively evaluated by alkalis leachability, with a higher alkali leachability indicating more obvious secondary efflorescence. VAE increases the concentrations of free alkalis ions including Ca2+, K+, Na+ of PCDM, improves the capacity of pore water transmitting ions, increases the alkalis leachability of PCDM, and accordingly promotes the secondary efflorescence of PCDM.
Key words: Portland cement-based decorative mortar (PCDM), redispersible vinyl acetate/ethylene copolymer powder (VAE), Secondary efflorescence, Alkalis leachability
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，pH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。
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DOI:
10.1631/jzus.A1300403
CLC number:
TU502
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On-line Access:
2015-02-03
Received:
2013-12-20
Revision Accepted:
2014-06-09
Crosschecked:
2015-01-23