Material estimation includes sand,
cement, coarse aggregate and steel for a particular mix design. Let us consider
a mix design of 1:2:4 for our estimation practice. The dry volume of total materials
required is considered as 1.54 times the wet volume of concrete. This is due to
the voids that are present in sand and aggregates in dry stage. Therefore, for
our calculation, we will consider the total volume of materials required as
1.54m3 for 1m3 of wet concrete.
a) Bags of cement required:
Volume of cement required for 1m3
of Concrete = (1 x 1.54) / (1 + 2 + 4) = 0.22m3
But the volume of one bag of
cement = 0.0347m3;
Therefore, the number of bags of
cement = 0.22 / 0.0347 = 6.34 bags of cement; Say, 7 bags.
b) Volume of Sand required:
Volume of sand required = (2 x
1.54) / (1 + 2 + 4) = 0.44m3 of sand.
c) Volume of Coarse Aggregate Required
Volume of Coarse Aggregate = (4 x
1.54) / (1 + 2 + 4) = 0.88m3.
d) Estimation of Reinforced Steel:
Quantity of steel required depends
on components of structure, i.e. slabs, beams, columns, foundations, roads etc.
To estimate the steel required, there are two methods:
The first method is, when we have
the drawings available, we can calculate the total weight of steel required,
and dividing it by the total volume of concrete for the different components.
This will give us the weight of
reinforcement steel per cubic meter of concrete for the different components.
The second method is assuming the
percentage of reinforcement for different components.
The following are the percentages
of reinforcement steels generally required for the different components. Its
values can vary from structure to structure, and can be assumed from past experiences
of similar structure.
For slabs = 1.0% of concrete
volume.
For Beam = 2% concrete volume.
For column = 2.5% of concrete
volume.
For Reinforced
concrete roads = 0.6% concrete volume.
Thanks.
ReplyDeleteIt was helpful.
You are welcome
DeleteQuestion:
ReplyDeleteIs the dry weight to wet weight volume ratio of 1.54 for concrete the same for that of cement-sand mortar.?
- Ken
Basically, the ratio of dry-weight volume to wet-weight volume used in calculating the quantities of materials used in known volumes of cement mortar is 1.54. (thus, the same with the value used in calculating the materials for concrete)
Deletehow we prove numerically factor 1.54 in mix design
DeleteDear Haseeb.
DeleteThe 1.54 ratio is a volume ratio. It is the ratio of the dry volume of the concrete materials to the wet volume.
Standard dry weights of the materials are batched according to the ratios in which they are required in the concrete, and the volumes are measured (both separately and when dry-mixed).
After the addition of water to the required consistency, the final volume is measured again.
The 1.54 factor had been proven long ago by engineers, and thus, there is no need proving it all over again, except for academic purposes.
For further research, you might try to consider if there are significant variations in the volumes of the separate materials before the dry mixing and after the dry mixing (before the addition of water)