CREEP, SHRINKAGE, AND THERMAL STRAINS IN NORMAL, MEDIUM, AND HIGH-STRENGTH CONCRETES DURING HYDRATION

This paper presents an experimental study on early-age shrinkage and t hermal and creep strains of normal (30 MPa), medium (70 MPa), and high -strength (100 MPa) concretes subjected to sealed and air-dried curing . It was found that demolding at very early ages resulted in greater s hrinkage and thermal strains in high-strength concrete than in medium strength concrete, which in turn showed greater strains than the norma l strength concrete. It was also observed that creep of the high-stren gth concrete containing napthalene-based superplasticizer is much more sensitive to the age of loading than the normal and medium strength c oncretes, with very early-age loading resulting in significantly highe r creep. Predictions using the CEB-FIP creep expressions agree reasona bly well with the measured creep strains, except for the case of high- strength concrete loaded at very early ages (i.e., less than 24 hr).