CONCRETE ESTIMATE

Estimating for the number of bags of cement and cu.m of sand and gravel is determined with the help of mixture ratios like class aa, class a, etc with corresponding number of bags per cu.m or per sq.meter computations.

Here's a sample calculator to compute for the needed bags of cement and volume of sand and gravel. Pilot test the excel file if there are any errors in values.

Used kilos of cement from computation is 40kg only.

Sample Computation:

➤ Footing size 1.50m x 1.50m x 0.25m

➤ no. of sets: 12

➤ use: class a mixture

1. Compute for Cement, Sand and Gravel needed

Compute for Volume

1.50m x 1.50m x 0.25m = ✔0.5625cu.m

a. Class A Mixture (1:2:4)

● In 1 cu.m you need 9 bags of cement, 0.50cu.m of sand and 1.0 cu.m of gravel

0.5625cu.m x 12 x 9 = ✔ 60.75bags of 40kg cement

0.5625cu.m x 12 x 0.50 = ✔ 3.375cu.m of sand

0.5625cu.m x 1.00 x 12 = ✔ 6.75cu.m of gravel

b. Volume Method (with 3000psi)

You may also try the Mixture Proportion (1:2:3:0.5) shared by Engineers

Cement

volume x 36

        3

Sand

volume

     2

Gravel

volume (as is just multiply to number of sets)

Water (where 0.50 x 40kg cement = 20kg)

0.5 or 20kg or 20 liters (1kg=1 liter)

Applying to above computed volume:

Cement

0.5625cu.m x 36

           3

= 6.75 bags x 12 sets

= ✔ 81 bags

Sand

0.5625cu.m

        2

= 0.28125cu.m x 12 sets

= ✔ 3.375 cu.m

Gravel

= 0.5625cu.m x 12 sets

= ✔ 6.75 cu.m

source: link to video

2. Concrete Hollow Blocks (CHB)

For the number of pieces of concrete hollow blocks (CHB) that comes in sizes like 3", 4", 5", 6", 8" is simple. (may vary per region)

You just need to get the area of the certain wall that requires CHB and multiply by 12.50pcs (or 13pcs) and that will give you the total pcs of CHB, regardless of thickness.

In 1.00 sq.m if you fit in your CHB of any size will accomodate 12.5pcs say ✔13pcs

Sample Computation:

➤ wall size 3.00m x 4.00m height
➤ CHB: 6"

Compute for needed CHB

3.00m x 4.00m = ✔ 12.00sq.m

12.00 x 13 = ✔ 156pcs 6" CHB

DIFFERENT SIZE

In case in your local area you have different size of hollow blocks, then simply get the length and height of your standard concrete hollow blocks and try to use this formula

1000mm/height of CHB = x

1000mm/length of CHB = y

total of CHB per square meter = x multiply with y

say you have 200mm x 200mm size CHB

1000/200 = 5pcs

1000/200 = 5pcs

in 1 square meter (1 sqm) = ✔ 25pcs of 200mm x 200mm (regardless of its thickness)

CHB Mortar

image of chb_from_source

Mortar Volume for 4" thk CHB sample

deducting the web thickness

=0.40-4(0.025)

=0.30 (will be your total length)

deducting the shell thickness

=0.10-2(0.025)

=0.05 (will be your thickness)

multiply both with CHB height

=0.30 x 0.05 x 0.20

=✔ 0.003cu.m per one piece CHB

Therefore, in 1 sqm CHB you have 0.0375cu.m of mortar needed to be filled.

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