To answer this question, let’s consider an example of a cube. The surface area to volume
ratio of a cube is=(6b^2/b^3) = 6/b where b is the length of the cube. This implies that the surface area to
volume ratio decreases with an increase in volume. Therefore, when the size of maximum aggregate is increased, the surface area to be wetted by water per unit volume is reduced.Consequently, the water requirement of the concrete mixes is reduced accordingly so that
the water/cement (w/c) ratio can be lowered. This will result in a rise in concrete strength.
But the dis advantage is that, because of these larger size of aggregates discontinues are created and the workability is very low.