Use the following information to complete the concrete mixture designs for the following question.
The following materials are available for a concrete mixture design:
ASTM C 150 Type I/II Cement
Relative density of 3.15
Coarse Aggregate: well-graded 3⁄4 in. maximum-size aggregate (MSA), crushed limestone, angular
Oven-dry specific gravity: 2.6
Absorption: 0.72%
Oven-dry rodded bulk density: 102 lb/ft3 Moisture content of coarse stockpile: 0.6%
Fine Aggregate: well-graded natural sand Oven-dry specific gravity: 2.5 Absorption: 1.3%
Moisture content of fine stockpile: 3.6% Fineness Modulus: 2.2
An air entraining admixture will provide enough air for the design mixture at a dosage rate of 3 oz/ft3
QUESTION:
Concrete is required for an 8 in thick exterior concrete slab in central Texas. A specified compressive strength, f’c , of 5000 psi is required at 28 days using an ASTM C 150 Type II portland cement. The design calls for a minimum of 2 in. of concrete cover over the reinforcing steel. The minimum distance between reinforcing bars is 3 in. A slump of 3 inches should be the target. The sidewalk is located in an environment that does not require air entraining. The concrete is required to have low permeability when exposed to water and moderate sulfates. The concrete will be exposed water soluble sulfates in soil at 0.14%. No statistical data on previous mixes are available.
Determine:
a. The theoretical mixture proportions of all concrete constituents (fine aggregate, coarse aggregate, water, cement, chemical admixtures) based on 1 yd3 of concrete on an oven dry basis for aggregates.
b. The as-batched mixture proportions based on the moisture contents provided in the materials available section.
c. How much of each material would be required to make a 20 ft long by 15 ft slab from the concrete mixture described above?