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Nominal maximum size of coarse aggregate

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Concrete is a widely used material. Reinforced concrete structures can be found everywhere. The main reason behind the popularity of reinforced concrete structure is the high strength and the long life span of these structures. Concrete and steel are combined to produce reinforced concrete. Concrete is good at compression while steel good at tension. Concrete and steel form a perfect combination to resist loads imposed on the structure.

Concrete is a composite material composed of cement, coarse aggregate, fine aggregate, and water. Admixtures can be used to enhance concrete properties. A concrete mix consists of almost 65% aggregates. Aggregates are classified into fine and coarse aggregates. Since the aggregates form the majority of a concrete mix. The quality of aggregates can greatly affect the strength and durability of concrete. Aggregates can be natural or crushed aggregates. Used aggregates should be strong, hard, and should not contain a large amount of organic matter or harmful material that can adversely affect the concrete mix's strength. 
Figure 1

According to ACI-318/5[3.3.2], the nominal maximum size of coarse aggregate shall not be larger than:
  1. 1/5 the narrowest dimension between sides of forms, nor
  2. 1/3 the depth of slabs, nor
  3. 3/4 the minimum clear spacing between individual reinforcing bars or wires, bundles of bars, individual tendons, bundled tendons, or ducts.
The limitation of aggregate maximum size is to ensure the smooth placing of concrete. If the maximum size of aggregate is above the limit, the placing of concrete can be difficult, and there will be a possibility of concrete segregation. The aggregate will be separated from the concrete. If the maximum size of aggregate is above the limit, the aggregates will be trapped by the reinforcement, which will cause separation of concrete ingredients. 

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My name is Mohammad Hamdan, and I am a Civil/bridge Engineer with extensive professional background and experience in the field of construction. I have 10+ years of experience in the construction field. During my professional career, my emphasis has been placed on structural projects, mainly bridges, infrastructure and roads. Reading and practicing the design of structures is my passion.i was lucky to be a part of a big team that executed major highway interchanges. I believe in spreading the knowledge, thus, i compose these courses to share my experience and knowledge. My course focuses on the practical side of construction field. On other word, i am sharing some of what new engineers need to know about construction field. Beside working on construction field, i love writing some articles on my website ( curious civil engineer) Moreover, i wrote some engineering papers, you can check them  by searching my name on Google (Mohammad mamon Hamdan)