What is the function of coarse aggregates in concrete?

The function of coarse aggregates in concrete is primarily to provide strength and volume. Coarse aggregates, which typically consist of materials such as gravel, crushed stone, or recycled concrete, play a crucial role in the structural integrity of concrete mixtures. They contribute significantly to the load-bearing capacity of the concrete due to their ability to resist compressive forces. By providing volume, coarse aggregates also help to reduce the amount of cement paste needed in the mixture, which can optimize the overall performance of the concrete while affecting its durability and sustainability.

Coarse aggregates also help achieve proper workability and consistency in the mixture, ensuring that the concrete can flow and fill forms adequately during placement. Their size and distribution influence the concrete's layout and its physical properties, including resistance to cracking and shrinkage.

The other options, while they can have some indirect effects on the overall concrete mix, do not capture the fundamental role of coarse aggregates as effectively as the correct answer. Reducing costs and improving aesthetics are secondary considerations, whereas the primary purpose is to enhance both the strength and volume of the concrete.