Materials Estimations of Building – Concrete volume and Mixing Ratio

By | November 16, 2018

Materials Estimation of Building.(MEB)

Concrete Volume Calculation

To calculate the amount of concrete that is needed for a particular job, we must be acquitted with the following

  • Mixing ratio
  • Density of ordinary Portland cement =1440kg/m3
  • Density of sharp sand and shipping or gravel.=1600kg/m3
  • 1000kg=1tonne
  • 1 tone = 0.63m3 for both sand and gravel
  • Water cement ratio = 0.5, 0.6, 0.7 etc

Mixing Ratio:

This has to do with the comparison of the quantity of each of the concrete constituent. The most commonly used mixing ratios are: (1) 1:2:4 (2) 1:3:6 (3) 1:3 (4) 1:6 these rations mentioned above, are applicable to a normal soil. Meanwhile, the number 3 and 4 ratios are mortar ration not concrete.

Interpretation of the Mixing ratios.

In the ration 1:2:4 the first figure “1“ represent a part of cement. The second figure “2” represents 2 parts of sharp sand while the last figure “4” represents 4 parts of shipping or gravel. These parts are measured with equipment. The most commonly used equipment is the head pan.

Materials Estimations of Building - Concrete volume and Mixing Ratio

 

NOTE: a bag of ordinary Portland cement contains two head pan by volume. Therefore, if we are to use a bag as a means of cement measurement then, the ration will take the form. 2:4:8. If this is reduced, it will give us 1:2:4. Therefore, it should be noted that when we are to produce a concrete with a bag of ordinary Portland cement, 4 head pan of sharp sand will be needed and not two. While shipping, will be eight head pan and not four. The same is applicable to 1:3:6 mixing ratio

Other equipment of measurement

Another mostly used measuring equipment is the wheelbarrow.

Materials Estimations of Building - Concrete volume and Mixing Ratio

It should be noted here that 4 head pan equals one wheelbarrow

The number of Materials needed to produce the quantity of concrete needed

Example 1

Calculate the material needed to cast (blind) a foundation of a total grid (perimeter) of 70 m if the trench width and blinding thickness (concrete thickness) is 450 mm  and 150 mm respectively. Use a mixing ratio of 1:2:4.

solution to concrete volume calculation-Material Estimation

First, convert all measurement to meters.

Length of trench =70 m

Width of trench = 450 mm = 0.45 m

Blinding thickness (height) = 150 mm = 0.15 m

  1. Volume of concrete = L x B x H = 70 x 0.45 x o.15 = 4.725 m3. after calculating the volume, increase it by 15% to canter for wastage:

100% volume = 4.725m3

Increase: 115% of 4.725 = 115/100 x 4.725/1 =5.43375 approximately 5.43 m3

Mixing ratio

Given ratio =1:2:4, sum of the ratio = 1+2+4 = 7

2) Volume of cement = 1/7 x 5.43 = 0.7757 m3, Density of ordinary Portland cement = 1440 kg/m3

Mass of cement = density x volume = 1440 x 0.7757 = 1117.008 kg

But one bag of cement = 50 kg, therefore, number of bags that will be needed = 1117.008/50 = 22.340

Therefore, the numbers of bags needed are bags of cement

3) Volume of sharp sand = 2/7 x 5.43 = 1.5514 m3

Density of sharp sand =  /m3

Mass of shape sand = density x volume = 1600 x 1.5514 = 2482.24 kg

But sand and gravel are measured in tone. 1000 kg = 1 tone. Therefore, 2482.24/1000 = 2.48 tone.

4) Volume of shipping (granite) = 4/7 x 5.43 = 3.1028 m3

Density of shipping 1600 kg

Mass of shipping = 1600 x 3.1028 = 4964.48kg

Since is measure in tone, 4964.48/1000 = 4.964 approximately, 5 tone.

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