#sieve analysis

The main measure of the structural quality of concrete is its compressive strength. This property of concrete is commonly considered in structural design. Depending on the mix and time and quality of the curing, the compressive strength of concrete can be obtained up to 95 MPa or more. Commercial production of concrete with ordinarily aggregate is usually in the 20 to 80 MPa range with the most common ranges for cast in place buildings from 20 to 40 Mpa. On the other hand, precast and pre stressed applications often expect the strengths of 25 55 MPa. Although concrete is not normally designed to resist direct tension, the knowledge of tensile strength is used to estimate the load under which cracking will develop. This is imputable to its influence on the formation of cracks and its propagation to the tension side of the reinforced concrete flexural member. Shear, torsion, and other actions also produce tensile stresses to the particular section of concrete members. In most cases, member behavior changes upon cracking. So the tension strength of concrete is also considered in the proportioning concrete member. This strength is of interest in designing of highway and airfield slabs as shear strength and resistance to cracking are very important to sustain such loading. The tensile strength of concrete is relatively low, about 10 to 15 of the compressive, occasionally 20 .