Abstract: 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.

Key words: low-heat cement, shrinkage performance, alkali, hydration process, hydration kinetics, pore structure