Optimization of Compressive Strength of Lime-Cement Concrete using Scheffe’s Regression Theory

In this paper, a regression model is formed to make the fore-telling of the compressive strengths and their compactible mix ratios for a lime-cement concrete as effective and perfect as possible using the Scheffe’s regression theory. Twenty four selected mix ratios were studied experimentally for their compressive strengths at ۲۸ days after curing in water at room temperature. Compressive strengths obtained stretched from ۱۵.۱۲N/mm۲ to ۲۴.۵۸N/mm۲. Fifteen of the readings obtained were used to develop the regression model while nine mix proportions were adopted for validation of the developed model. The model was tested for reliability at ۹۵ % level of confidence using the F-statistic test and found to be adequate as the calculated F-value (۱.۹۱۸) was less than the critical F-value (۳.۴۳۸). A MATLAB based computer program was written based on the regression model using visual basic ۶.۰ software to optimize the compressive strength of the lime cement concrete and also speed up the process of selecting the corresponding mix ratios. The peak value of compressive strength predictable by the model is ۲۴.۴۶۰۳۳۶ N/mm۲ and the corresponding mix ratio is ۰.۵۸۶:۰.۸۴۱:۰.۱۵۹:۲.۴۲:۴.۸۴ (water: cement: lime: sand: granite chippings). MATLAB program developed is interactive, quick and is suitable for application in optimum concrete mixture proportioning.

Keywords:

Scheffe’s regression theory , Compressive strength , Lime-cement concrete , Mix ratios