Concrete does not have well defined elastic and plastic regions due to its brittle nature .A maximum compressive stress value is reached at relatively low strain and is maintained for small deformation until crushing occurs. The stress-strain relationship for small deformation until crushing occurs the stress-strain relationship for concrete is a nonlinear curve. Thus, the elastic modulus varies continuously with strain. the secant modulus at service load is normally used to define a single value for the modulus of elasticity. This procedure is given in most concrete texts. Masonry has a stress-strain diagram similar to concrete but is typically of lower compressive strength and modulus of elasticity