STRESS-STRAIN CURVES OF NORMAL AND LIGHTWEIGHT CONCRETE IN COMPRESSION.

A relatively simple experimental technique is used to obtain the stress-strain curves of concretes up to a strain of 0. 006. The stress-strain curves of normal weight concretes of strengths up to 11,000 psi and lightweight concrete of strengths up to 8000 psi are reported. An analytic expression for the stress-strain curve of concrete is developed to reflect experimental results. The analytic expression has four constants which depend on the properties of both the ascending and the descending portions of the stress-strain curve and can be evaluated from the knowledge of four key points of the curve. The coordinates of the four key points were expressed in function of the compressive strength of concrete so as to allow prediction of the entire curve solely from the knowledge of the compressive strength.