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1. Estimate the number of bags of cement and the volume in cu. m. of sand, andgravel required for the 10 cu. m. of concrete of 1:2:3 mixed if 5 gallons of water

per bag of cement are used.

UNIT WEIGHT SPECIFIC GRAVITY

CEMENT 94 lb/ft3 3.10

SAND 105 lb/ft3 2.65

GRAVEL 100 lb/ft3 2.70

SOLUTION:

Vcement =

= 0.486 cu. ft. Vsand =

= 1.27 cu. ft.

Vgravel =

= 1.781 cu. ft. Vwater =

= 0.486 cu. ft.

Vtotal = (0.486 + 1.27 + 1.781 + 0.486) cu. ft.

Vtotal = 4.205 cu. ft.

No. of bags of cement =

= 83.983 / 84 bags

Volume in cu. m.:

Vsand =

= 4.757 cu. m.

Vsand =

= 7.136 cu. m.

2. Determine the quantities by weight of cement, sand and gravel for one cu. yd.batch of concrete 1:2:4. If 20 L of water is used. The materials used have the

following characteristics 1 bag of cement = 42 kg., 1 cu. ft. of sand = 48 kg., and

1 cu. ft. of gravel = 45 kg. Specific gravity is 3.1 for cement, 2.7 for sand, and 2.7

for gravel.

SOLUTION:

cement = x

= 92. 6

Vcement =

= 0.4787

cu. ft.

sand = x

= 105.82

Vsand =

= 1.2562

cu. ft.

gravel = x

= 99.207

Vgravel =

= 2.355

cu. ft.

Vwater =

= 0.66845 cu. ft.

Vtotal

= (0.4787 + 1.2562 + 2.355 + 0.66845) cu. ft.

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Vtotal = 4.75835 cu. ft.

No. of bags of cement =

= 5.674 bags

Volume in cu. ft.:

Vsand = = 11.348 cu. ft.

Vgravel = = 22.696 cu. ft.

Weight in lb.:

Wcement =

= 525.41 lb.

Wsand =

= 1200.85 lb.

Wgravel = 4

= 562.92 lb.

3. A batch of concrete consisted of 150 lb. fine aggregates, 250 lb. coarseaggregate, 94 lb. of cement, and 5 gallons of water. The specific gravity of sand

and gravel is 2.6 and that of cement is 3.10.

(a) What was the total volume of concrete produced?(b)What was the weight of concrete in place per cubic foot?

WEIGHT SPECIFIC GRAVITY

CEMENT 94 lb 3.10

SAND 150 lb 2.60

GRAVEL 250 lb 2.60

SOLUTION:

(a)s =

; mat = s w W = V ; V =

cement = 3.10 (62.4

) = 193.44 pcf Vsand =

= 0.486 cu. ft.

sand = 2.60 (62.4 ) = 162.24 pcf Vsand = = 0.925 cu. ft.

gravel = 2.60 (62.4

) = 162.24 pcf Vsand =

= 1.541 cu. ft.

Vwater =

= 0.486 cu. ft.

Vtotal = (0.486 + 0.925 + 1.541 + 0.486) cu. ft.

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Vtotal = 3.62 cu. ft.

(b)Wtotal = Vtotal ; =

=

Wtotal = (250 + 150 + 94) lb. + (0.668 cu. ft.) (62.4

) = 147.98

Wtotal = 535. 68 lb.

4. An air entraining concrete is to be designed by a water cement ration of about 6gallons per bag of cement with approximately 2.5 cu. ft. of sand, and 3.5 cu. ft.

of gravel per bag of cement, and with an air content of 4%. The specific gravity

of sand and gravel is 2.65 and the specific weight of cement is 3.14. The unit

weights of sand and gravel are 110 lb. respectively and that of cement is 94 lb.,

determine the weight of each ingredient required to produce 1 cu. yd. of

concrete without reducing the strength of a mixture having water cementration of 6 gallons.

UNIT WEIGHT SPECIFIC GRAVITY

CEMENT 94 lb/ft3 3.14

SAND 110 lb/ft3 2.65

GRAVEL 110 lb/ft3 2.65

GIVEN:

Ratio = 1:2.5:3.5

Water = 6 gal. /bagVair = 0.04Vtotal

SOLUTION:

Vcement =

= 0.48 cu. ft. Vsand =

= 1.663 cu. ft.

Vgravel =

= 2.328 cu. ft. Vwater =

= 0.802 cu. ft.

V= (0.48 + 2.328 + 1.663 + 0.802) cu. ft.

V= 5.273 cu. ft.

Vtotal = V + 0.04 Vtotal

Vtotal = 5.273 + 0.04 Vtotal

Vtotal = 5.493 cu. ft.

No. of bags of cement =

= 4.915 bags

Volume in cu. ft.:

Vsand = = 13.73 cu. ft.

Vgravel = = 19.23 cu. ft.

Wcement =

= 462.05 lb.

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Wsand =

= 1351.74 lb.

Wgravel =

= 1892.43 lb.

Wwater =

= 205.03 lb.