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Method-1: DLBD method to determine material requirement for 1 Cum concrete
The DLBD (Dry Loose Bulk Densities) method is an accurate method to calculate cement, sand and aggregate for a given nominal mix concrete. This gives accurate results as it takes into account the Dry Loose Bulk Densities of materials like Sand and Aggregate which varies based on the local source of the material
For calculation, We consider a nominal concrete mix proportion of 1:2:4 (~M20).
Step-1: Calculate Weights of Materials Required
To arrive at different quantities of concrete ingredients, the Dry loose bulk density of materials plays important role as they are batched loosely.
Considering Dry loose bulk density of following concrete ingredients as
Cement = 1440 kg/cum ; Fine Aggregate = 1600 kg/cum ; Coarse Aggregate = 1450 kg/cum ; Water = 1000 kg/cum
The dry loose density varies for
Considering a concrete mix proportion (by volume) of 1:2:4
i.e., Cement: Fine aggregate (Sand) : Coarse Aggregate is in the ratio of 1:2:4 by volume.
Cement required = 01 bag = 50 kg ~ 36 liters or 0.036 cum
Fine Aggregate required = 2*0.036 ~ 0.07 cum = 0.072*1600 = 115 kg
Coarse Aggregate required = 4*0.036 ~ 0.14 cum =0.144*1450 = 209 kg
Considering water – cement ratio (w/c) of 0.55 , water = 0.55*50 kgs = 27.5 kg
Step-2: Calculate Material Requirement for Producing 1 Cum Concrete
The volume proportion in weight turns out to be
Cement : Sand : Aggregate (in Kgs) is 50 kgs : 115 kgs : 209 kgs (by weight)
Water required for the mixture = 27.5 kgs
Total weight of concrete ingredients = 50+115+209+27.5 = 401.5 say 400 kg
Density of concrete = 2400 kg/cum
So, 1 bag of cement produces = 400/2400 = 0.167 cum
No. of bags required for 01 cum of concrete = 1/0.167 = 5.98 bags ~ 6 bags
From above, if the concrete mix is 1:2:4 , to get a cubic meter of concrete we require
1.Cement = 6 bags = 300 kgs.
2.Fine Aggregate = 115/0.167 = 689 kg
3.Coarse Aggregate = 209/0.167 = 1252 kg.
4.Water = 300/0.55 = 165 kg.
Like wise other concrete mix with varying proportions and materials with different physical properties ,the individual quantities of different ingredients can be easily arrived.