Estimation of Cement, Sand, and Gravel in Construction

Estimation of Cement, Sand, and Gravel in Construction

In the estimation of cement, sand, and gravel volumes for concrete proportioning, we use the Fuller's Formula. This is an easy way to get a rough estimate in case you are in the field.

Let:

C = number of bags of cement per cubic meter of concrete work  (bag/m3)

S = volume of sand per cubic meter of concrete work  (m3 of sand /m3)

G = volume of gravel per cubic meter of concrete work  (m3 of gravel /m3) 

c,s,g = cement-sand-gravel ratio (relative amounts of solids by volume in a mixture)

C = 55 / (c+s+g)

S = 0.028*C*s

G = 0.028*C*g

The classes of concrete mixture depends on the cement-sand-gravel ratio (c:s:g).

Class A (1:2:4) = for beams, slabs, columns, all members subjected to bending

Class B (1:2.5:5) = member not reinforced for bending stress

Class C (1:3:6) = for footing (not under water)

Note: We use here 94 lbs Portland Cement per cubic meter of concrete

Example 1:

Determine the number of bags of cement, sand, and gravel of a proposed concrete pavement whose width and length are 100 m x 200 m. The thickness is 100 cm.

Given: Width = 100 m         Length = 200 m               Thickness = 0.1 m

Reqd: number of bags of cement, sand, and gravel

Solution:

Volume of concrete = 100 * 200 * 0.1 = 2000 m3

Pavement = Class A (1:2:4)

C = 55 / (c+s+g) = [ 55 / (1+2+4) ] * 2000 = 15,680 bags

S = 0.028*C*s = {0.028*  [ 55 / (1+2+4) ] * 2 } * 2000 =  800 m3 of sand

G = 0.028*C*g = {0.028*  [ 55 / (1+2+4) ] * 4 } * 2000 = 1760 m3 of sand