Measurement of chemical shrinkage of cement paste: Comparison study of ASTM C 1608 and an improved method

Chemical shrinkage of cementitious materials has significant contribution to the early volume change of concrete, therefore, precise measurement of chemical shrinkage of cementitous materials is increasingly concerned. In the present study, measurement methods for chemical shrinkage were reviewed, especially for dilatometry method specified in ASTM C 1608. It was found that the precision and repeatability of ASTM C 1608 method were significantly influenced by the water to cement (w/c) ratio and the thickness of cement paste, which can be attributed to the generation of voids in the cement matrix and the restraint of formed particle skeleton structure, especially when low w/c ratio and/or high thickness of cement paste were used. By adding a magnetic stirring bar to prevent the formation of skeleton structure of cement paste, the chemical shrinkage measurement was simplified and presented superior precision and repeatability than ASTM C 1608 method, and the obtained results had better correlation with the calculated chemical shrinkage.