聚合物改性砂浆凝结时间与自由收缩变形的协调

关键字：砂浆,聚合物,凝结时间,塑性自由收缩

（宜昌三大工程建设项目管理有限责任公司，湖北 宜昌  443002）
 

    摘要：研究了基于自由收缩变形特征砂浆凝结时间的确定方法，测试了掺量为5%、10%、15%、20%EVA乳胶粉改性砂浆塑性自由收缩变形-时间演变规律，并与采用贯入阻力法测试的凝结时间进行了对比分析，由此确定砂浆的凝结时间及所对应的自由收缩变形量。并通过差热分析测试，研究了EVA乳胶粉对砂浆的改性机理。结果表明，在各EVA掺量下，砂浆均呈现先膨胀后收缩的变形特征；EVA能降低早龄期砂浆的有效自由收缩变形量，并延长砂浆的凝结时间，延迟有害变形的发生，且掺量越多，效果越明显；由塑性自由收缩试验法测得的砂浆凝结时间（Ta）要早于贯入阻力法测得的砂浆凝结时间（Ts），前者更能真正反映砂浆材料由塑性流动状态向半/固体状态的转变过程；EVA乳胶粉能降低水泥水化产物中Ca（OH）2吸热峰的起点温度、峰温和峰值面积，延缓水泥水化，且掺量越多，效果越明显。
    关键词：砂浆；聚合物；凝结时间；塑性自由收缩
    中图分类号：TU528        文献标识码：A        文章编号：1001-702X（2017）06-0044-04

Study on harmory between setting time and free shrinkage displacement of mortar modified by polymer
LIU Sichun
（Yichang Three Major Construction Project Management Co. Ltd.，Yichang 443002，China）

    Abstract：This paper studied the determination method of setting time of mortar based on the characteristic of free shrinkage deformation，the evolution rule of the plastic free shrinkage deformation with time of mortars modified by 5%，10%，15%，20% EVA powder was measured. Compared setting time with the test method of penetration resistance，the setting time and its corresponding free shrinkage deformation was determined. The experimental results show that the deformations behavior of mortars with different EVA contents all the first appear plastic swelling and then exhibit shrinkage. EVA powder reduces the effective free shrinkage deformation，prolong the mortar setting time，delay the occurrence of harmful deformation，and the more content，the more obvious effects. The mortar setting time by free shrinkage deformation test（Ta） is earlier than by penetration resistance test（Ts）. And the former could be more truly reflect the transformation process of mortar from the plastic flow state to the semi/solid state；EVA powder can reduce the starting temperature，the peak temperature and the area of Ca（OH）2 endothermic peak and delay the cement hydration，and the more dosage，the more obvious effect.
    Key words：mortar，EVA polymer，setting time，plastic free shrinkage