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 thermal 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 shrinkage and thermal strains in high-strength concrete than in medium strength concrete, which in turn showed greater strains than the normal strength concrete. It was also observed that creep of the high-strength concrete containing napthalene-based superplasticizer is much more sensitive to the age of loading than the normal and medium strength concretes, with very early-age loading resulting in significantly higher creep. Predictions using the CEB-FIP creep expressions agree reasonably 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).