Effect of Size
Variation in the size of Aggregates changes the water demand, cement content, micro-cracking (strength) in concrete. It also effects pumpability, and durability of concrete.
Effect of Grading
Grading of aggregates depends on the proportions of coarse and fine aggregate. If grading of aggregate is varied, it also changes cement paste content (cost economy), workability of the mix, density and porosity.
It is an important factor and has a maximum influence on workability. Well graded aggregates result in the least amount of voids in a given volume. Less voids result in excessive past availability in a unit volume and more lubrication. Hence the mix is cohesive and avoids segregation.
Effects of Surface Texture
Surface texture of aggregates itself depends on rock hardness, grain size, porosity, previous exposure and affects workability, paste demand, initial strength of concrete. Shape and surface texture affects usually the properties of freshly mixed concrete. Rough-textured and elongated particles require more cement paste to produce workable concrete mixtures, thus increasing the cost. This factor is of secondary importance. Porous aggregates require more water compared to non absorbent aggregates for achieving same degree of workability.
Effects of absorption & Surface Moisture
Affects the following concrete behaviors: Mix-design, soundness of concrete & strength/abrasion resistance.
Shape of aggregates:
Angular aggregates increases flakiness or elongation thus reduces workability. Round smooth aggregates require less water and less lubrication and greater workability in a given w/c ratio.
Effect of Coarse Aggregate on Strength of Concrete
Coarse aggregate makes up about 75% of concrete by volume. Strength of concrete is also affected by the properties of coarse aggregates besides water-cement ratio and other properties. The lower the water to cement ratio, the more the effect of coarse aggregates on the strength of concrete. Undesired properties of coarse aggregate may affect the strength, durability, and performance of concrete negatively