What is the formula for calculating void content in concrete?

The formula for calculating void content in concrete primarily focuses on determining the space within a concrete mix that is not occupied by solid material. The correct approach involves using the relationship between the bulk specific gravity of the aggregate, the density of water, and the bulk density of the aggregate.

The correct answer employs the formula: 100[(bulk specific gravity X density of water) - Bulk Density of agg.]. Here’s why this formulation works:

1. Understanding Bulk Specific Gravity: The bulk specific gravity of the aggregate essentially tells you how much mass of the aggregate is present per volume when submerged in water. By multiplying the bulk specific gravity by the density of water, you obtain the weight of that volume of aggregate in water terms.

2. Bulk Density of Aggregate: This is the actual weight per unit volume of the aggregate as it is being weighed in its natural state (including voids).

3. Calculation of Voids: By subtracting the bulk density of the aggregate from the weight derived from the bulk specific gravity and density of water, you isolate the amount of space in the concrete that is not filled with solid particles, which represents the void content.

Therefore, the formula effectively quantifies the voids by showing the difference