水泥石的干燥收缩及其与水化程度的关系

通过梯次干燥的方式测定了水泥石在干燥过程中的重量损失和收缩变化,并结合TG-DSC综合热分析研究了水泥石水化程度与干缩的关系。结果表明,水泥石水化程度随龄期延长而逐渐提高。随着水化程度增大(由0.55到0.81),水泥石100%~84%湿度范围内收缩减小,在84%~54%收缩增大,在54%~7%湿度范围内的收缩和总收缩先增大,后有减小趋势。再润湿以后,水泥石的重量损失可以回复,但一部分干缩不可逆,大部分不可逆干缩发生在84%~54%和54%~7%湿度范围内。干燥过程改变了水泥石的孔结构,使水泥石毛细孔粗化,凝胶孔塌陷减少。

Relationship between hydration degree and drying shrinkage of cement pastes

The relationship between hydration degree and drying shrinkage of cement paste was studied by measuring the shrinkage and weight loss of cement paste during step-wise drying experiments and determining the hydration degree from the results of TG-DSC.It is identified that hydration degree increases with increasing curing time.As hydration degree increases（from 0.55 to 0.88）,shrinkage in the 100-84% RH ranges decreases while shrinkage in the 84-54% RH range increases.Shrinkage in the 54-7% RH range and the total shrinkage increases at first and then tends to decrease.Upon rewetting,the weight loss can be regained while a portion of the shrinkage is irreversible.Most part of the irreversible shrinkage occurs in the 84-54% and 54-7% RH ranges.Drying process coarsens the capillary pores and minimizes the volume of gel pores of cement paste.