Evidences of chemical interaction between EVA and hydrating Portland cement
Evidences of chemical interaction between EVA and hydrating Portland cement
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DOI：
10.1016/s0008-8846(02)00805-0
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发表时间：
2002-09-01
影响因子：
11.4
通讯作者：
Gleize, PJP
中科院分区：
文献类型：
--
作者：
Silva, DA;Roman, HR;Gleize, PJP
尽管乙烯/乙酸乙烯酯共聚物（伊娃）在砂浆和混凝土生产中广泛使用，但是在各种研究人员中对于水泥和聚合物相之间的相互作用的种类没有达成一致。因此，采用适当的措施来实现最终产品质量，以及将其属性调整为所需的性能是受损的。本研究的目的是通过对伊娃共聚物改性水泥浆体的微观结构表征来填补这一知识的不足。制备了具有不同伊娃含量的波特兰水泥浆体。水/水泥比保持恒定。将糊剂置于两种不同的固化条件下，并在28天后进行分析。进行了热分析（差热分析[DTA]和热重[TG]分析）、傅里叶变换红外光谱（FT-IR）和扫描电子显微镜（SEM）测试，从而允许评价伊娃对水泥水化的影响。胶凝相和聚合相之间的化学相互作用的一些证据被确定。结果表明，伊娃共聚物的醋酸酯基团发生碱水解，与浆料中的Ca 2+离子发生相互作用，生成有机盐（醋酸钙）。氢氧化钙含量降低，钙矾石晶体似乎形成良好，并观察到许多Hadley颗粒。富钙，多孔和六方结构相被检测到，可能是由于乙酸的氢氧化钙晶体的攻击。(C)2002爱思唯尔科技有限公司版权所有。
In spite of the widespread use of ethylene/vinyl acetate copolymer (EVA) in mortar and concrete production, there is no agreement among various researchers about the kind of interaction that is developed between cement and polymeric phases. Therefore, the adoption of adequate measures for Final product quality achievement is impaired, as well as the adjustment of their properties to the desired performance. The purpose of this research is to fill this lack of knowledge through the microstructural characterization of cement pastes modified with EVA copolymer. Portland cement pastes were prepared with different EVA contents. The water/cement ratio was kept constant. The pastes were submitted to two different curing conditions, and analyzed at 28 days old. Thermal analyses (differential thermal analysis [DTA] and thermogravimetric [TG] analysis), Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM) tests were performed, which permitted the evaluation of the EVA effects on the cement hydration. Some evidences of chemical interactions between cementitious and polymeric phases were identified. The results showed that the acetate groups of EVA copolymer undergo alkaline hydrolysis and interact with Ca2+ ions of the pastes to form an organic salt (calcium acetate). The calcium hydroxide content is decreased, the ettringite crystals appear to be well formed and many Hadley's grains were observed. A calcium-rich, porous and hexagonal structure phase was detected, probably due to acetic acid attack on calcium hydroxide crystals. (C) 2002 Elsevier Science Ltd. All rights reserved.