What is meant by the term 'compaction' in concrete?

The term 'compaction' in concrete refers to the process of reducing the volume of concrete, which is crucial for eliminating air pockets and voids within the mix. This is essential for increasing the density and strength of the concrete, ensuring it achieves optimal performance during its lifespan. Compaction is typically achieved through various methods, such as vibrating, rodding, or tamping, and is an important step in the placement of concrete, as it directly influences the structural integrity and durability of the final product.

The other choices focus on different aspects of concrete mixing and finishing. Mixing concrete involves combining the dry ingredients with water to create a slurry. Adding ingredients refers to the process of incorporating additional components, such as additives, that may enhance specific properties of the concrete. Finishing the surface pertains to the techniques used to achieve a desired texture or appearance for the surface once the concrete has set, which are all important but distinct from the concept of compaction.