Measurement of Volume Change in Cementitious Materials at Early Ages

Abstract

Early-age cracking in concrete bridge decks, pavements, and superstructure elements has served as the impetus for substantial research on early-age shrinkage in cementitious materials. Much of this research has indicated how mixture proportions, constituent materials, and construction operations can be altered to reduce the risk of cracking. Unfortunately, many unrestrained shrinkage-testing protocols do not provide a comprehensive picture of the early-age shrinkage exhibited by cementitious materials, especially those used in higher-strength concrete. In this paper, the authors review several early-age shrinkage testing procedures. A testing protocol is presented to show how chemical shrinkage can be measured by using buoyancy measurements. A comparison of the measured autogenous shrinkage is made by using four measurement methods: a sealed membrane, a corrugated tube, a noncontact measurement in a rigid mold, and the ASTM C 157 standard. The results of the autogenous and chemical shrinkage tests are compared with one another to describe fully early-age length change. It is shown that through careful experimentation and interpretation, the results of these tests can be completely correlated with one another. This can provide the end user with reliable test procedures to compare different paste compositions and different admixtures and can provide inputs for models that quantify cracking potential.