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采用自行设计的试验装置对可再分散醋酸乙烯-乙烯共聚物乳胶粉改性水泥砂浆(EVA改性砂浆)早龄期收缩应力/应变变化规律进行了初步研究,用X射线衍射对其水化产物钙矾石(AFt)、氢氧化钙(CH)和水化铝酸钙(C_4AH_(13))进行了表征,分析了收缩应力、应变变化与EVA掺量(质量分数)、水化产物的关系.结果表明:EVA可使改性砂浆早龄期收缩应力的增长速率变缓、最大收缩应变减小,且EVA掺量为15%时效果最明显;EVA既能抑制C_4AH_(13)的生成和转化,也能抑制AFt和CH的生成,并延缓水泥砂浆水化进程;在水化3h内,EVA改性砂浆的收缩应力变化只受AFt生成量的影响,而其收缩应变变化同时受CH和AFt生成量的影响,且与CH的相关性更大.
The shrinkage stress / strain change of redispersible vinyl acetate-ethylene copolymer latex powder modified mortar (EVA modified mortar) at early age was studied by a self-designed test device. The X-ray diffraction (AFt), calcium hydroxide (CH) and hydrated calcium aluminate (C_4AH_ (13)) were characterized. The effects of shrinkage stress, strain change and EVA content (mass fraction) The results show that: EVA can make the growth rate of shrinkage stress of aged mortar slow down and the maximum shrinkage strain decreases, and the effect is obvious when EVA dosage is 15%; EVA can inhibit the formation of C_4AH_ (13) And also inhibited the formation of AFt and CH, and slowed down the hydration process of cement mortar. Within 3h of hydration, the shrinkage stress of EVA-modified mortar was only affected by the amount of AFt produced, while the shrinkage strain was also affected by CH And the effect of AFt production, and the correlation with CH is greater.