Concrete is widely used for the construction of various types of structures and is made by materials that come all from the earth’s crust. However, the resource of these natural materials is depleting, and it is nowadays important to find a substitute to them. A solution of this problem can be the use of agricultural waste materials that can be locally available. For example, Rice Husk Ash (RHA) is the residue of completely incinerated rice husk, that is the covering part of the grain of rice. Rice husk is abundant in many parts of the world, and is classified as a highly reactive pozzolana, so it can be used as a partial replacement of cement. During the years, researchers have studied the mechanical properties and the durability of the concrete incorporating different percentage of RHA. The objective of the study presented in this paper is not only to find the "perfect percentage" of RHA replacement, but also to find a new expression for calculating the concrete compressive strength, considering the percentage of RHA replacement. From the comparison on the experimental studies done by other researchers on the concrete compressive strength, the reliability of the here proposed expression is evaluated, and it has found to be in better agreement with the test results, indicating that the here proposed expression has certain universality and can accurately describe the effect of the RHA replacement on concrete strength.
