Prediction of Flexural Strength of Rice Husk Ash Concrete

Abstract

Pozzolanas are materials containing reactive silica and/or aluminum. When the material is mixed with lime in powdered form and in the presence of water, it will set and harden like cement though with higher initial setting time than Ordinary Portland Cement (OPC), Rice Husk Ash (RHA) is a form of natural pozzolana. It is found locally in abundance in Nigeria and in other parts of the world. Udeala (2003), produced a mix containing RHA with 45 per cent slaked lime. This work uses Scheffe's (1958) simplex theory to optimize the flexural strength of concrete made from RHA pozzolan based on (4,2) simplex lattice. The strengths predicted by the model are in good agreement corresponding experimentally obtained values. The statistical student's t-test was used to test the adequacy of the model equation. The results are in affirmative. With the model, any desired strength of hardened concrete, given any mix proportions, is easily evaluated. Conversely, the various mix proportions matching any stipulated strength are with their also easily obtained. The computer program is written in BASIC language.