Introduction into Mix Ratio Matrix Analysis of Concrete for the Determination of Cement Grade

Abstract

This paper presents a novel method to determine the grade of cement from concrete instead of mortar by a simple 2X2 Mix Ratio Matrix Analysis of Concrete. Two stages are involved in the model. The first is to determine the actual cement strength and gross aggregate strength while the second stage is to convert this cement strength from 150mm cubes to its equivalent strength if  50mm cubes with the aid of conformity factors of 1.435 which has been established earlier. Three batching methods where considered viz: Batching by weight, volume and the modified volume method (The modification implied here is the complete removal of entrained air in each of the concrete constituents during volume batching before mixing. Here the air volume was removed by increasing the volume of each constituent to make up for the volume of air entrained). Concrete samples produced for the work was from 42.5 grade Dangote brand of cement indicated in the bag. The model was tested with compressive strength for Fifty (54) concrete samples of 1:1.5:3 mix ratio which was batched by the traditional volume method and the modified volume method with Water cement ratio maintained at 0.5 and cured for 7 days, 14 days and 28 days. The results show that Dangote cement has a strength in the range of 34.04mpa and 36.6mpa (48.85mpa and 52.52mpa equivalent of 50mm cubes) and the cement grade is actually 42.5 as claimed by the manufacturer. A range of 43.95mpa and 45.56mpa was computed from the concrete, which is less than the next grade of cement 52.5. This strength of the Dangote cement as obtained was confirmed on compressive strength results of another set of 307 samples batched by weight and prepared for 1:2:4 and 1:1.5:3 by the authors. The Compressive strength result of cubes produced from other literature for 1:3:6 and 1:2:4 when tested in the proposed model revalidates this same result for Dangote cement while giving the strength of different brands of cement i.eIbeto, Elephant, Purechem, and Unichem.