Concrete Mix Designs – An Overview

Table 1 0 Tristar Concrete

 

 

 

 

 

 

 

Above is a basic concrete mix design from a concrete supplier. The five main materials in this mix are sand, course aggregate, cement, BASF (water reducing admixture), and water as shown in the “Material” column. The “Description” and “Source” give detail on the material and the supplier.

“ASTM” stands for “American Society for Testing & Materials”. ASTM is an international standards organization that publishes technical standards for materials, services, products, & systems. More specifically, ASTM lays out the material standards for what is acceptable in concrete mix designs.

“Specific gravity” is a ratio comparing the density of a substance to a standard, such as water. Concrete has a general weight of 150lb/ft^3. Figure 1 shows a total weight of 4,132lb/yd^3. When converted this comes out to 148.6lb/ft^3.

 

Table 2 Tristar Concrete

Specified F’c is the compressive strength of the concrete.

Specified Slump is the workability of the concrete. The concrete supplier or third-party materials testing company administers a “slump cone test” to check the slump of the concrete. This is a quality control measure to assure the concrete meets the mix design’s standards.

Specified Air & Designed Air is the amount of air in the concrete. This mix design is a footing and interior slab non-air entrained mix design. Any remaining air in the concrete is known as entrapped air.

Designed Unit Weight is the average weight of concrete (150lb/ft^3).

Design W/C + P Ratio is the water cement ratio plus polyheed (water reducing admixture). The water cement ratio is very important to the mix design. Too much water and the concrete will end up cracking due to excessive evaporation and shrinkage. Not enough water and the concrete will difficult to place and finish.

Designed Volume shows that 27.47 ft^3 or 1 yd^3 was mixed and tested for this specific mix design.