Prediction and Optimization of Compressive Strength of Sawdust Ash-Cement Concrete Using Scheffe’s Simpex Design

Frequent increase in the price of cement and other building materials across Nigeria has reawakened serious need to relate research to production, especially in the use of locally available materials as alternatives for construction of functional but low-cost dwellings in both rural and urban areas in the country. This article aimed at prediction and optimizing compressive strength of concrete when one of its conventional materials, cement is partially or wholly replaced by Sawdust ash. Sawdust ash (SDA) is a non-toxic construction waste material found in abundance in Nigeria. The effective utilization of this material as a component in concrete depends on the mix proportioning of the various component materials. A mathematical model to predict and optimize compressive of Sawdust ashcement concrete was developed using Scheffe’s five component second degree simplex lattices. The model was used to optimize the compressive strength of concrete made from water, cement, sawdust ash, sand and granites. The results of the response function compared favourably with the corresponding experimental results and the predictions from the response function were tested for adequacy using the statistical student’s t-test and found to be adequate at 95% confidence level. The optimum compressive strength of concrete at twenty-eight (28) days was found to be 20.44N/mm 2 . This strength corresponds to a mix ratio of 0.5: 0.95: 0.05: 2.25: 4 (i.e. water: cement: sawdust ash: sand: granites). With the optimization function developed in this work, any desired compressive strength of sawdust ash-cement concrete can be predicted from known mix proportions and vice versa.