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.

## 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

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 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

**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.