how many pounds of sand will you need with the following batch design of on cubi
ID: 1844183 • Letter: H
Question
how many pounds of sand will you need with the following batch design of on cubic yard? the concrete will have air entrainment. yoy haveasked to develop a mix design for 1cy with the folowing requirements. desired strength of 4732 psi concrete. The Sp. gravity of the fine agg is given as 2.85. the fineness modulus of the fine aggregate is 2.58. the courese aggregate has a sp gr of 2.47. a max aggregate size of 3/4" , and a dry rodded weight of 123. the air content is to be 4% and theslump is 3 to 4 inch.
Explanation / Answer
Assume standard deviation s = 4 MPa
calculate the mean strength
Design strength 4732 psi = 33MPa
K is constant
Mean strength = design strength + Ks
= 33 + 1.64 x 4
= 39.46
1) Refer table 11.5 from ACI 211.1.91, for 39.46 MPa mean strength, air entrained, the water cement ration w/c = 0.38
2) refer table 11.8 ACI 211.1.91, for a slump of 76mm to 101mm, 20mm maximum size of aggregate, water content is 200 kg/m3
3) Cement content =water content/(w/c)
= 526 kg/m3
4) refer table 11.4 ACI 211.1.91, for 20mm max size of aggregate, fineness modulus 2.58, the bulk volume of coarse aggregate is 0.65
Dry rodded bulk density of coarse aggregate = 123 lb/ft3 = 1970 kg/m3
Weight of coarse aggregate = 0.65 x 1970
= 1280 kg/m3
5) Refer table 11.9 ACI 211.1.91, for 20mm maximum size of aggregate air entrained concrete, the estimated density of fresh concrete = 2280 kg/m3
weight of water = 200 kg/m3
weight of cement = 526 kg/m3
weight of coarse aggregate = 1280 kg/m3
weight of fine aggreagte = 2280 - (200+526+1280)
= 274 kg/m3
hence the required weight of sand is 274 kg/m3 or 7389.47 ounce/cubic yard
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