| 摘要: |
| 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(C4AH13)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C4AH13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. |
| 关键词: 改性砂浆 醋酸乙烯乙烯共聚物乳胶粉(EVA) 收缩应力/应变 水化产物 相关性 |
| DOI：103969/j.issn1007 9629201605001 |
| 分类号: |
| 基金项目:国家重点基础研究发展计划(973计划)项目(2011CB013800)；“十二五”国家科技支撑计划项目(2012BAJ20B02) |
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| Shrinkage Stress Strain Evolution of Mortars Modified by EVA Polymer at Early Age |
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LIU Sifeng, WAN Tingting, WANG Peiming
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Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education, Tongji University, Shanghai 201804, China
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| Abstract: |
| A setup of testing the shrinkage stress and strain for cement mortars was designed. The evolutions of the shrinkage stress and strain of the mortars modified by EVA polymer were studied. Meanwhile, the hydration products of AFt, Ca(OH)2, C4AH13 were characterized by X ray diffraction, the effect of EVA polymer addition on hydration process of mortars at early age were analyzed. The relationship between the development of shrinkage stress strain and EVA addition and the relationship between the hydration products of AFt, Ca(OH)2 and EVA addition were discussed. The results show that the addition of EVA causes the growth of shrinkage stress of mortar to slow down in advance and the maximum shrinkage strain reduces, and the effect of 15% EVA content(by mass) is more significant. Addition of EVA polymer delays the early hydration process of cement and reduces shrinkage stress/strain through inhibiting the formation and transformation of C4AH13, as well as the formation of AFt and Ca(OH)2. The trend analysis indicates that the shrinkage stress development of mortar modified by EVA polymer is affected by the amount of AFt in cement paste only within 3h, but not directly related to Ca(OH)2. The shrinkage strain development of mortar modified by EVA polymer was affected by the amount of Ca(OH)2 and AFt in cement paste, and more related to Ca(OH)2 at early age. |
| Key words: modified mortar vinyl acetate ethylene copolymer redispersible powder(EVA) shrinkage stress/strain hydration product relativity |
