OPTIMUM MIX DESIGN FOR MINIMUM CONCRETE STRENGTH REQUIREMENT USING AVAILABLE AGGREGATE FROM AKURE, NIGERIA

Abstract

In concrete engineering, strength of concrete is one of the important indexes that concrete engineers should know. The strength has been found based on linear programming technique called linear optimization using Computer Microsoft Excel Spreadsheet Solver which was used for the purpose of concrete mix proportioning in the mix design method. In general, a number of trial concrete mixes were also used before obtaining a target mix proportion. According to the properties required, it takes at least one month or more in order to achieve enough strength satisfaction. Based on the results of the experimental work conducted in this present research work for optimizing a typical concrete mixture using locally available ingredient (Akure pit-sand), the optimum CA/TA and TA/C ratios are found to be 0.46 and 3.9, respectively. The compressive strength, fcu at 28 days using mix ratio 1:2.1:1.8 was obtained to be 10.13 N/mm2 with water-cement of 0.72. Also, the probability that the event of this result will be obtained or occur under the same conditions was calculated to be 0.829 that is 82.90%. Since the compressive strength of the concrete at 28 days used in the design of reinforced concrete sections to obtain the Ultimate Moment of resistance could not be obtained as recommended by BS8110; part1; 1997. Therefore, the Modified Ultimate Moment of resistance ( = 0.084 ) obtained in this research work is proposed