EFFECT OF COARSE AGGREGATE GRADING ON PROPERTIES OF CONCRETE

Abstract

Coarse aggregates have a great effect on properties of concrete, so gradation of coarse aggregates will always end up giving concretes of different properties. This project is an effort to provide properly detailed information concerning the influence of coarse aggregates grading on properties of concrete. Chippings of sizes 10mm, 20mm and 25mm were selected and used for this work. Preliminary tests like sieve analysis were conducted on the fine aggregate (sand) andalso on the three selected coarse aggregates. 10mm and 25mm coarse aggregates were mixed in various proportions to produce five different concretes. Concrete C1 [100% of 10mm + 0% 25mm coarse aggregates], concrete C2 [75% of 10mm + 25% of 25mm coarse aggregates ], concrete C3 [50% of 10mm + 50% of 25mm coarse aggregates], concrete C4 [25% of 10mm +75% of 25mmcoarse aggregates], and concrete C5 [0% 10mm + 100% 25mm coarse aggregates], Another concrete, [concrete C6] was casted with only 20mm and used as check, as 20mm coarse aggregate is mostly used in construction. In each mixture, slump test was performed and six cubes casted. The cubes were cured in water, and at 7days and 28days the selected cubes were crushed to obtain their compressive strength. After all the crushing it was found that the compressive strength increases as the percentage of 25mm coarse aggregate increases in a mixture, while workability decreases as the percentage of 25mm increases in each mixture. Additionally, the sieve analysis graphs of the fine and coarse aggregates, the slump histogram of the three coarse aggregates and the graph of the concretes' compressive strengths, all went a long way in throwing more light on the properties of all the concretes.