• Ismaeel H. Musa Albarwary Dept. of Road Construction, Duhok Polytechnic University
  • Ziyad N. Shamsulddin Aldoski Dept. of Building and Construction, Duhok Polytechnic University
  • Lawend K. Askar Dept. of Highway and Bridges, Duhok Polytechnic University
Keywords: Concrete, aggregate size


Aggregates form 60% to 75% of concrete volume and thus influence its mechanical properties.   The strength of normal concrete is affected by the maximum size of a well-graded coarse aggregate by two opposing ways. Concrete mixes containing larger aggregate particles needs less mixing water than those containing smaller aggregates. On the other hand, the smaller size aggregates give larger surface area for bonding with the mortar matrix. This study is a trial to cover these two points with testing three different useable concrete mixes in Kurdistan Region–Iraq which are 1:1.5:3, 1:2:4 and 1:3:6 (Cement: Sand: Gravel). In each mix, five maximum  aggregate sizes were used which are 9.5mm, 12.5mm, 19mm, 25mm and 37.5mm , the consistency of the all mixes is fixed for slumps of 25-50mm . According to the test results it is concluded that in general the compressive strength of concrete increases when the maximum size of aggregate decreases and the maximum aggregate size strongly influences the concrete strength. Test results also show that the optimum concrete strength is reached by using aggregates of 9.5mm maximum size. We further concluded that for a specified strength, an economical mix can be produced by decreasing the amount of cement and using an appropriate maximum aggregate size.


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1. In general the concrete compressive strength increases when the maximum size of aggregate decreases.
2. The maximum aggregate size strongly influences the concrete strength.
3. The optimum compressive strength of concrete is reached by using aggregates of 9.5mm maximum size.
4. For concrete of cement to aggregate ratio below (6), the compressive strength is more affected by the change in the aggregate size than the cement content.
5. For a specified strength, an economical mix can be produced by increasing the cement to aggregate ratio and decreasing the maximum size of aggregate.
6. Lean mixes can be used for structural purposes when using small sized aggregates.

The authors are very grateful to the two technicians Mr. Heja Ahmed and Mr. Khalid Khalil, who are working in concrete Laboratory at Duhok Technical Institute for their assistance in testing the concrete cubes.

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How to Cite
Albarwary, I. H. M., Aldoski, Z. N. S., & Askar, L. K. (2017). EFFECT OF AGGREGATE MAXIMUM SIZE UPON COMPRESSIVE STRENGTH OF CONCRETE. Journal of Duhok University, 20(1), 790-797. https://doi.org/10.26682/sjuod.2017.20.1.67