The effect of changes in proportions of the fine and coarse aggregate or the quantity of cementitious material on the strength

Q. What is the effect of changes in proportions of the fine and coarse aggregate or the quantity of cementitious material on the strength?

A. Strength primarily depends on the w/cm, regardless of changes in proportions of aggregate or the quantity of cement, provided that the aggregates are clean and structurally sound, and the mixture is plastic and workable. Changes that increase the proportions of the coarse and fine aggregate usually also increase the fractional volume of aggregate in the mixture, which improves resistance to shrinkage and generally lowers cost by reducing cementitious material paste content. In general, an increase in the proportion of fine aggregate results in an increase in the water requirement, causing the workability and strength to be reduced unless more water and cementitious material are added to maintain the w/cm specified.

References: SP-1(02)

Topics in Concrete: Concrete Fundamentals; Quality Assurance; Testing of Concrete