Building Construction Handbook, Eighth Edition

Concrete Batching ~ a batch is one mixing of concrete and can be

carried out by measuring the quantities of materials required by

volume or weight. The main aim of both methods is to ensure that

all consecutive batches are of the same standard and quality.

Volume Batching ~ concrete mixes are often quoted by ratio such

as 1 : 2 : 4 (cement : fine aggregate or sand : coarse aggregate).

Cement weighing 50 kg has a volume of 0„033 m^3 therefore for the

above mix 2 ¾ 0„033 (0„066 m^3 ) of sand and 4 ¾ 0„033 (0„132 m^3 )

of coarse aggregate is required. To ensure accurate amounts of

materials are used for each batch a gauge box should be employed

its size being based on convenient handling. Ideally a batch of

concrete should be equated to using 50 kg of cement per batch.

Assuming a gauge box 300 mm deep and 300 mm wide with a

volume of half the required sand the gauge box size would be †

volume = length ¾width ¾ depth = length ¾ (^300) ¾ 300
length =widthvolume
¾depth

=0„30„033

¾0„3

= 0„366 m

For the above given mix fill gauge box once with cement, twice

with sand and four times with coarse aggregate.

An allowance must be made for the bulking of damp sand which

can be as much as 33^1 / 3 %. General rule of thumb unless using dry

sand allow for 25% bulking.

Materials should be well mixed dry before adding water.

Concrete Production---Volume Batching