Good quality aggregate is essential for producing high-quality concrete. It must be clean, hard, strong, and have durable particles that are free from any absorbed harmful chemicals, clay coatings, or other contaminants that could affect cement hydration or reduce paste-aggregate bonding. Classification is the process of determining the particle size distribution for the aggregate. Leveling limits and maximum aggregate size are specified as these properties affect the amount of aggregate used, as well as cement and water requirements, workability, pumpability, and concrete durability.
Generally speaking, if the water-cement ratio is chosen correctly, a wide range of ratings can be used without a major impact on strength. When specifying void graded aggregates, certain particle sizes are omitted from the aggregate size continuum. Gradual separation aggregates are used to obtain uniform textures in concrete with exposed aggregate. It is important to maintain strict control of mix ratios to avoid segregation.