Proportion a concrete mix (ACI 211.1) based on the following conditions and mate
ID: 1921159 • Letter: P
Question
Proportion a concrete mix (ACI 211.1) based on the following conditions and materials: reinforced concrete retaining wall in Chicago, IL. The average 28-day compressive strength is 4000 psi. The wall is 14 in. thick with a minimum clear space of 3 in. High frequency vibration is used. Materials available are (choose the best ones): Portland Cement: Type I, Type 111, Type V Sand: F.M. 2.50; bulk sp. gr. (4) = 2.62, contains 2% free surface moisture based on ssd state. Crushed granite: three max sizes available: 1 in., ¾ in., ½ in. Each size has a dry ro unit weight of 97 lb/ft3, a bulk sp. gr. (4 of 2.64, absorption (dry) = 0.7%, and contains 1% free surface moisture based on the ssd state. Admixtures: vinsol resin, calcium chloride Report the name and weight of cement, water, and aggregates (in pounds per cubic yard) for making a 1 yd3 trial batch with these materials. Select admixture(s).Explanation / Answer
Use Portland cement Type I
mean strength fm = fmin +ks
consider standard deviation s = 4MPa
fmin = 4000 psi = 28MPa
fm = 28+ 1.64 x 4
= 34.56MPa
2) refer able 11.5 of ACI 211.1-91 to estimate the w/c ratio
for man compressive sreangth of 35 MPa, air entrained concrete w/c ratio is 0.4
3) refere table 11.8 ACI 211.1-91 to estimte water content
assume a slump o 20mm, and use 20mm size that is 3/4inch of aggregate
the water content is 165 kg/m3 (278.11 lb/yd3 )
4) cement content = 165/0.4
= 412.5 kg/m3 (695.29 lb/yd3 )
5) from table 11.4 ACI 211.1-91 for 20mm size of aggregate, fineness modulus 2.5, the bulk volume of dry rodded coarse aggregate is 0.65
6) dry rdded unit weight of 97 lb/ft3 = 1554 kg/m3
weigh of coarse aggregte = 0.65 x 1554
= 1010.1 kg/m3 (1702.57 lb/yd3 )
7) first estimateof density of concrete from table 11.9 ACI 211.1-91 is 2280 kg/m3
8) therefore weight of aggregate = 2280 - (1010.1+412.5+165)
= 2280-1587.6 = 692 kg/m3 (1166.4 lb/yd3 )
Use Ordinary portland cement 33 grade, type 1 cement
weigh of cement = 695.29 lb/yd3
weight of water = 278.11 lb/yd3
weight of aggreagte = (1166.4 +1702.57) = 2868.97 lb/yd3
Use Vinsol resin admixture
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