Comparison of prediction provisions for drying shrinkage and creep of normal-strength concretes

Abstract

Calculating the response of concrete structures to loads that change with time, strain recovery under removal of load, relaxation of stress under constant strain, and redistribution of internal moments in indeterminate structures requires equations to predict the shrinkage and creep of concrete. Current North American practice would be to use the recommendations of American Concrete Institute ACI 209-82. The 2002 version of Eurocode 2 endorsed the use of the 1999 version of the 1990 Comité Euro-international du Béton (CEB) model code MC1990-99 shrinkage and creep equations. Bažant and Baweja and Gardner and Lockman have proposed prediction methods, known as B3 and GL 2000, respectively, to replace the current ACI 209-82 provisions. The practitioner needs to know what method would be appropriate in what circumstances, what input information is required, and what is the probable uncertainty. This paper compares the shrinkage and creep predictions of ACI 209-82, CEB MC1990-99, B3, and GL 2000 with the experimentally measured results given in the Réunion Internationale des Laboratoires et Experts des Matériaux, Systèmes de Constructions et Ouvrages (RILEM) data bank for normal-strength concretes.Key words: concrete, creep, modulus of elasticity, shrinkage, strength development.