Early Age Creep and Shrinkage of Concrete with Shrinkage Reducing Admixtures (SRA)

Early age creep and shrinkage are primary factors that influence premature cracking of concrete affecting the durability and performance of concrete structures. Shrinkage of concrete causes tensile stress development while tensile creep works as a stress relaxing mechanism and relieves part of the stress developed due to shrinkage. Shrinkage Reducing Admixtures (SRA) have been effectively used to reduce the potential for cracking, particularly at early age. However, the effects of SRA on stress development and tensile creep require more testing. This study provides experimental data on early age creep and shrinkage of normal and high performance concrete. Concrete mixtures with and without SRA were tested using a uniaxail test configuration that allowed to measure creep and shrinkage under constant load as well as under increasing load (restrained condition). Concrete containing a Shrinkage Reducing Admixture (SRA) has been evaluated using a constant load creep-shrinkage test. SRA was added at a dosage rate of 3.71 l/m3 (0.75 gal/yd3). The results showed that the SRA at the tested dosage significantly reduced the early age shrinkage of concrete. The results also indicated that the SRA influenced the shrinkage and creep in a different manner.