Question

(8 points) Consider casting a concrete driveway 40 feet long, 12 feet wide and 6 in. thick. The proportions of the mix by weight are given as 1:2:3 for cement, sand, and gravel with w/c of 0.50. The specific gravities of sand and gravel are 2.60 and 2.70 respectively. Entrained air content is 7.5%. How many pounds of cement, water, sand, and gravel are needed for the driveway?

Answer 1

Answer:

Weight of cement = 10909.08 pounds

Weight of sand = 18008.64 lb

Weight of gravel = 28051.92 lb

Weight of water = 5454.54 lb

Explanation:

given data

length = 40 feet

width = 12 feet

thickness = 6 in = 0.5 feet

mix proportion = 1:2:3

specific gravity of cement = 3.15

specific gravity of sand = 2.60

specific gravity of gravel = 2.70

water to cement ratio = 0.50

solution

first we get here total volume that is

volume = length × width × thickness    ...........1

volume = 40  × 12 × 0.5

volume = 240 feet³

and

now we get here dry volume of concrete that will be

Dry volume =  wet volume ×  1.54    .......................2

Dry volume = 240 × 1.54

Dry volume =  360 feet³

and

we have given air content entrained is = 7.5 %

so required volume will be as

required volume = Dry volume × ( 1 - 7% )    .............3

required volume = 360 × ( 1 - 7.5 % )

required volume = 333 feet³  

and

total ratio is

total ratio = 1+ 2+ 3

total ratio = 6

so volume of sand cement and gravel will be

volume of  cement = $\frac{1}{6} \times 333$  

volume of  cement = 55.5 feet³

volume of  sand  = $\frac{2}{6} \times 333$

volume of  sand  = 111 feet³

volume of  gravel = $\frac{3}{6} \times 333$  

volume of  gravel = 166.5 feet³

and

now we get here weight of sand cement and gravel as

weight = volume ×  specific gravity × density of water   .............4

and now put here value and we get

Weight of cement = 55.5 × 3.15 × 62.4

Weight of cement = 10909.08 pounds

and

Weight of sand = 111 × 2.60 × 62.4

Weight of sand = 18008.64 lb

and

Weight of gravel = 166.5 × 2.7 × 62.4

Weight of gravel = 28051.92 lb

and

Weight of water = 0.5 of weight of cement

Weight of water  = 0.5 ×  1090.9.08

Weight of water = 5454.54 lb