Na碱和K碱对低热水泥收缩性能的影响

Influence of Sodium Alkali and Potassium Alkali on the ShrinkagePerformance of Low Heat Cement

通过分别外掺Na2SO4(Na碱)和K2SO4(K碱)的方式,将低热水泥的总碱含量提高至0.8%,1.2%和1.6%,研究了不同碱含量和不同碱类型对低热水泥干燥收缩和自收缩的影响,并从水化动力学和孔结构方面,探究了不同碱含量和不同类型碱对低热水泥收缩性能的影响机制。结果表明,碱促进了低热水泥的干燥收缩和自收缩,这种促进作用不可忽略,且对自收缩影响时效短于干燥收缩,而以K2SO4形式存在的碱更易促进低热水泥干燥收缩和自收缩。基于水化动力学和孔结构研究,不同类型碱对低热水泥收缩性能的影响机制在于:碱促进了低热水泥结晶成核和晶体生长过程,细化了孔结构,增加了与收缩性能相关的孔分布,而以K2SO4形式存在的碱,能使这种促进作用和细化作用更加明显。该研究可为精细化提高混凝土耐久性提供数据支撑。

The influence of type of alkali on the drying shrinkage and autogenous shrinkage of low-heat cement was investigated in this paper.By adding different dosages of Na2SO4(Na alkali)and K2SO4(K alkali),the total alkali content of low-heat cement was increased to 0.8%,1.2%,and 1.6%respectively.The mechanism of different types of alkali in varied content affecting the shrinkage performance of low-heat cement was examined in terms of hydrokinetics and pore structure.Results illustrated that alkali could promote the drying shrinkage and autogenous shrinkage of low-heat cement,and such promotion should not be neglected.This effect on autogenous shrinkage required less time than that on drying shrinkage did.Besides,alkali in the form of K2SO4 was more likely to promote the drying shrinkage and autogenous shrinkage of low-heat cement.What’s more,alkali could promote the crystal nucleation and crystal growth stage of low-heat cement that led to the refinement of pore structure and the increment of pore distribution related to shrinkage properties.Such refinement and increment were more apparent when alkali existed in the form of K2SO4.The research finding offers data support for improving the durability of concrete.