Concrete Structures: Vincent Chu Answers
In designing concrete structures, normally maximum aggregate sizes are adopted with ranges from 10mm to 20mm. Does an increase of maximum aggregate size benefit the structures?
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 ratio can be lowered, resulting in a rise in concrete strength.
However, an increase of aggregate size is also accompanied by the effect of reduced contact areas and discontinuities created by these larger sized particles.
In general, for maximum aggregate sizes below 40mm, the effect of lower water requirement can offset the disadvantages brought about by discontinuities as suggested by Longman Scientific and Technical (1987).