Cellular concrete is a lightweight concrete that contains uniformly distributed air pockets or gas cells provided by stable preformed foam measured from a calibrated nozzle. Cellular concrete commonly includes a sand aggregate, although some mixtures may use lightweight aggregates such as fly ash, expanded clay, shale, and several others. The mixture becomes a lightweight concrete from the large amount of entrapped air due to the mixing process of the concrete materials and the foaming agent. These air bubbles are generally macroscopic, rather than microscopic air bubbles found in air-entrained concrete. Some of the current commercial uses for cellular concrete include cast-in-place purposes, thermal and sound insulation fills, and precast element development.
Cellular Concrete Mix Design Procedure
1. Calibration Test. The goal of the calibration test for cellular concrete is to find the foam-pumping rate and the volume ratio of foam to air. A container of a known volume and weight is first overfilled with the preformed foam from a pressurized hose. The amount of time to overfill the container is recorded, as well as the weight of the overfilled container. The foam is then leveled off so that it is only filled to the brim of the container. After doing so, the container is then weighed for a second measurement. From interpolation, the calculated level time can be found, and thus so can the foam-pumping rate. The foam density can be calculated from the weight and volume parameters found earlier in the procedure, as well as the volume ratio of foam to air. The volume ratio of foam to water is calculated by finding the volume of water in the foam, subtracting that value from the total volume of container to find the volume of air, and then dividing the total volume by volume of air.
2. Determine Cement Content. The cement content is found by first calculating the total weight of the design by multiplying the density based on a volume of 1 cubic yard by 27 cubic feet. The cement content is found by multiplying the calculated total weight by 1 minus the specified water to cement ratio.
3. Determine Total Water Content. The total water content is found by simply subtracting the cement content by the calculated total weight.
4. Determine Volume of Air and Foam. The volume of air is found by applying the absolute volume method to find the volume of air. Using the volume ratio of foam to air from the calibration test, the volume of foam can be calculated.
5. Determine Water in Foam. The total weight of water in foam is calculated by simply multiplying the volume of foam by the foam density found in the calibration test.
6. Determine Water Added with Cement. The water added with cement is calculated by subtracting
