To arrive at different quantities of concrete ingredients, the Dry loose bulk density of materials plays important role as concrete ingredients are batched loosely in volume proportion.
![Ratio of Cement, Sand and Coarse aggregate used in Concrete](https://happho.com/wp-content/uploads/2017/03/Ratio-of-Cement-Sand-and-Coarse-aggregate.png)
How to Determine Dry Loose Bulk Density of Materials
a. Calculating Dry Loose Bulk Density of Cement
Cement being a factory made product and packaged in Bags weighing 50 kg each,its DLBD more or less fall around 1400 kg/cum.
Note: 1 cum = 1000 liters
For 50 kg (01 bag cement) the volume arrived is
1400 kg cement occupies Volume of 1 cum or 1000 liter (DLBD = 1400 kg/cum)
50kgs of cement will have volume, = 50/1400 = ~ 36 liter
Alternatively you can find the dry loose density as follows:
Have a 20 liter (V1) capacity container
![Calculating Loose Density of Cement](https://happho.com/wp-content/uploads/2017/03/Weight-Measurement.png)
Take its empty weight = W1
Fill loosely cement in the container to the full height, measure weight of container with cement = W2
Density= Mass/Volume = (W2 – W1) / (V1) = ‘x’ Kg/liter
DLBD of Cement = ‘x’ Kg/liter
For arriving at DLBD of Aggregates/Gravel, repeat the above procedure with coarse aggregate (stone chips) and fine aggregate (Sand).
Note: Ensure the aggregate are dry (sand if wet will be bulky, bulkiness depend on wet %), filled loosely not compacted (at site practically not feasible to compact concrete ingredients for each batch of concrete) and to the full height of the container.
![Measuring Aggregate at Site](https://happho.com/wp-content/uploads/2017/03/Measuring-Aggregate-at-Site.jpg)
![Measuring Fine aggregate (Sand) at Site](https://happho.com/wp-content/uploads/2017/03/Measuring-Sand-at-site.jpg)
Measuring Coarse and Fine Aggregate at Site using Measuring Box
B. Calculation of Number of Bags of Cement for 1 Cum Concrete
Considering Dry loose bulk density of following concrete ingredients as
Cement = 1400 kg/cum = 1.4 kg/ltr.
Fine Aggregate = 1600 kg/cum or 1.6 kg/ltr.(depends on source, gradation)
Coarse Aggregate = 1450 kg/cum = 1.45 kg/ltr. (Depend on source, type, shape, size)
Water = 1000 kg/cum = 1 kg/ltr.(Universal Constant)
Considering a concrete mix proportion (by volume)
1:2:4:: cement: fine aggregate : Coarse Aggregate
Cement required = 01 bag = 36 liters (36 cc) = 50 kg
For batching ease, the farma/measuring box, dimensions should be selected to match volume of a cement bag i.e. 36 liter or 36 cc (cubic centimeter), as the cement is added per bag
![Measuring Box Size (used to batch concrete)](https://happho.com/wp-content/uploads/2017/03/Measuring-Box-Shape.png)
Box size = 40cmx30cmx30cm = 36 cc (Cubic cm)
Fine Aggregate required = 02*36 = 72 ltr. = 72*1.6 = 115 kg
Coarse Aggregate required = 04*36 = 144 ltr.=144*1.45= 209 kg
Considering, water – cement ratio (w/c) of 0.55, water = 0.55*50 = 27.5 kg
The volume proportions (1:2:4) turns out to be
50 :115 : 209 :: 1: 2.3 : 4.18 by weight, Water= 27.5
Total weight of concrete ingredients = 401.5 say 400 kg
Density of concrete = 2400 kg/cum
01 batch (1:2:4) produces = 400/2400 = 0.167 cum of concrete
No. of bags required for 01 cum of concrete = 1/0.167 = 6 bags
From above, if the concrete mix is 1:2:4(by volume), to get a cubic meter of concrete we require
- Cement = 6 bags = 300 kgs.
- Fine Aggregate = 115/0.167 = 689 kgs = 15.2 cft
- Coarse Aggregate = 209/0.167 = 1252 kgs = 30.5 cft
- Water = 300/0.55 (w/c) = 165 kg/liter.
Likewise other concrete mix with varying proportions and materials with different physical properties, the individual quantities of different ingredients can be easily arrived.