Concrete is required for a sidewalk in NJ. A specified compressive strength, fc, of 3800 psi is required at 28 days using an ASTM C 150 Type I 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. The slab is 4 in thick. A slump of 5 inches should be the target. The sidewalk located in a severe climate . No statistical data on previous mixes are available.
Materials Available:
ASTM C 150 Type I/II Cement Relative density of 3.15
Coarse Aggregate: well-graded % in. maximum-size aggregate (MSA), local river gravel Oven-dry specific gravity: 2.8 Absorption: 0.87% Oven-dry rodded bulk density: 96 lb/ft3 Moisture content of coarse stockpile: 0.60%
Fine Aggregate: well-graded natural sand Oven-dry specific gravity: 2.4 Absorption: 2.0% Moisture content of fine stockpile: 5.0% Fineness Modulus: 2.6
A commercially available air-entraining admixture is supplied. The manufacturer recommends 3 fl oz per 100 lbs of cement as a dosage range which will give the required air content. In your design you should recommend a target value of +/-1 % of the desired air content. However, your design should be based on the maximum value . Determine:
a. The theoretical mixture proportions of all concrete constituents 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 concrete would you need for 20 feet of sidewalk
