Title: Creep and Creep Recovery of Concrete under High Compressive Stress
Author(s): A. M. Freudenthal and Frederic Roll
Publication: Journal Proceedings
Appears on pages(s): 1111-1142
Keywords: no keywords
Four series of tests studied creep and creep-recovery of concrete under sus-tained compressive stresses varying between approximately 15 and 65 percent of the 28-day compressive strength. Test specimens, loaded at 28 days, were cylinders 10 in. high, 3 and 4 in. in diameter, made with four different mixes. The creep tests were conducted under conditions of controlled temperature and humidity. Shrinkage of unloaded control specimens in the same environment was recorded so that the actual creep curves (total time dependent deformation minus shrinkage) could be obtained. Supplementary compression tests were conducted to determine the effect of sustained load on strength and modulus of elasticity of the concrete. To reproduce and represent the observed creep and creep-recovery curves, a mechanical model was introduced consisting of four elements, each represent-ing a specific type of contribution to total creep. Model constants were evaluated and their variation with respect to mix and applied stress determined. Using creep equations derived from the model, creep was predicted for four stress levels of each mix of Series IV. The equations were also used for evaluating stress relaxation from various stress levels.