**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 m3 therefore for the above mix 2 x 0.033 (0.066 m3) of sand and 4 x 0.033 (0.132 m3) 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 x width x depth = length x 300 x 300

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 331/3%. General rule of thumb unless using dry sand allow for 25% bulking.

Materials should be well mixed dry before adding water.

## No comments:

## Post a Comment