Abstract
Aggregates form 60% to 75% of concrete volume and thus influence its mechanical properties. The strength of (normal or high-strength) concrete is affected by the maximum size of a well-graded coarse aggregate. Concrete mixes containing larger coarse aggregate particles need less mixing water than those containing smaller coarse aggregates, In other words, small aggregate particles have more surface area than a large aggregate particle. In this research, about twenty-two mixtures were covered to study the effect of the MSCA, on compressive strength of (normal strength concrete) and Sixteen mixtures to study the effect of the maximum size of coarse aggregate on compressive strength for (high strength concrete). The concrete mixture is completely redesigned according to the maximum size of coarse aggregate needs and maintaining uniform workability for all sizes of coarse aggregate. The American design method was adopted ACI 211.1, for normal concrete. ACI 211-4R, the design method was adopted for high strength concrete. And use the MSCA with dimensions (9.5, 12.5, 19, 25, 37.5, and 50) mm for normal strength concrete and the MSCA (9.5, 12.5, 19, and 25) mm for high strength concrete. The slump was fixed (75-100) mm for normal strength concrete. Slump is fixed to (25-50) mm for high strength concrete before added Superplasticizer high range water reducer (HRWR). With Fineness Modulus (F.M) fixed to 2.8 for both normal concrete and high-strength concrete. According to the results of the tests, the compressive strength increases with the increase in the MSCA, of the normal concrete and also high – strength concrete. And the effect of the MSCA, on the compressive strength of normal concrete, is higher than that of high-strength concrete.
Highlights
Concrete is widely used in the construction of buildings, bridges and other infrastructure around the world.Concrete is affected by the components involved in production, and since coarse aggregate occupies a large part of the volume
The concrete is affected by the maximum size of a well-graded coarse aggregate, a concrete mixture containing large coarse aggregate particles has a small surface area compared to small coarse aggregate particles On the other hand, and the smaller coarse size aggregates give larger surface area for bonding with the mortar matrix
The US Code Tables American Concrete Institute (ACI) 211.1 were used to obtain the requirements for the maximum size of coarse aggregate in a volume unit .for normal strength concrete;
Summary
Concrete is widely used in the construction of buildings, bridges and other infrastructure around the world.Concrete is affected by the components involved in production, and since coarse aggregate occupies a large part of the volume. The study in this research completely redesigns the mixture according to the maximum size of the coarse aggregate used. This method differs from previous research, as an increase in the value of the compression strength amount and maintaining the same average workability of mixtures Several researches had been done on the effect of the MSCA on concrete strength. Kozul and Drawin (1997) studied the compressive strength and fracture of concrete and how the aggregate type, size, and content affects these concrete properties. They used basalt or crushed limestone aggregate with sizes of 12 or 19 mm. They concluded that for both normal and high-strength concretes the compressive strength is little affected MSCA, while the flexure strength of the both concretes is not affected by the MSCA [2]
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