Question

7) You are working on a concrete mix design that requires each cubic yard of concrete to have a 0.45 water–cement ratio,2100 lb/yd3 of dry gravel, 250 lb/yd3 of water, and 5% air content. The available gravel (NMS = ¾”) has a specific gravity of 2.6 , moisture content of 2.5% and absorption of 4.5%.The available sand has a specific gravity of 2.4, a moisture content of 2.5% and absorption of 2%. Air entrainer is to be included using the manufacturers specification of 0.1 fl.oz / 1% air / 100 lb cement. For each cubic yard of concrete needed on the job, calculate the weight of cement, moist gravel, moist sand, and water that should be added to the batch. Summarize and total the mix design when finished. 8) Design a concrete mix for the following conditions and constraints using the absolute volume method: Design Environment : Non-air entrained concrete will be used to cast Concrete frame. Required design strength(5000 psi) Minimum dimension (10 in.) Minimum space between rebars (1.5 in.) Minimum cover over rebars (2.5 in.) Standard deviation of compressive strength (600 psi) , (25 samples) Available Materials Cement Type II , moderate exposure Coarse aggregate Nominal Maximum size 1 in. river gravel (round) Bulk oven dry specific gravity =2.65, absorption = 3%, oven dry density 110 pcf , Moisture content 2%. Fine aggregate : Natural sand , Bulk oven-dry specific 2.5 , Absorption = 1% , Moisture content = 0.5% , Fineness modulus = 2.80

Answer 1

Final Weights for 8,

1. Water : 349 lb/yd^3

2. Cement: 780 lb/yd^3

3. Coarse aggregate: 2030 lb/yd^3

4.Fine aggregate : 844 lb/yd^3