Abstract:
Concrete is the most important engineering material in the world, and the addition or replacement of some of the concrete contents may change the properties of the concrete. The purpose of this study is to investigate the feasibility of using gabbro aggregates and granite stone as a coarse aggregate in concrete mixes. An experimental program is set up to test the effect of gabbro aggregate content and its combinations with granite stone with variation of percentages in concrete mixes. Firstly the source aggregate properties were considered in this study: specific gravity, moisture content and absorption for coarse aggregates and fine aggregate. And sieve analysis test was carried out before mix design. The mix was designed by british standard method, Characteristic Compressive strengths 25 (N/mm2). Different aggregate percentage combinations were used in this study for gabbro aggregate and granite stone (0%, 100%), (25%, 75%), (50%, 50%), (75%, 25%), (100 %, 0%) respectively. six mixes (one is control mix concrete mix by using natural coarse aggregate and five mixes contain the different percentage of gabbro and granite stone). 9 specimens cube from each mix were tested at (7, 28, 56) curing days. The tests included measurement of workability and compressive strength.
The results of the tests indicate a general improvement in mix properties (workability and compressive strength) with the introduction of gabbro aggregates in the mix. And the mix (100% gabbro) gave the high value of compressive strength and workability. The results showed that the rate of increase in compressive strength was 31.81% at 7 days, 16.13% at 28days and 17.8% at 56 days when comparing control mix with the mix (100% gabbro).
