Why the surface area of aggregate increases as the particle size decreases?
The increase in surface area with the decrease in aggregate particle size is demonstrated below:
Figure (a) shows: one 25.0 mm cube of aggregate: surface area= 6 x 25.0 x 25.0 = 3750 mm2
Figure (b) shows: eight 12.5 mm cubes of aggregate: surface area= 6 x 12.5 x 12.5 x 8 = 7500 mm2 and
Figure (c) shows: sixty-four 6.25 mm cubes of aggregate: surface area= 6 x 6.25 x 6.25 x 64 = 15,000 mm2
If a large coarse aggregate particle is reduced to fine sand size particles, the same volume would have a surface area about 100 times greater than that of the original cube.