Batching of Water:

The quantity of water must be measured accurately as the quantity of water plays an important role in governing the various properties of concrete particularly the workability of fresh concrete and the strength of hardened concrete. Water is commonly measured through volume, as it is more convenient to take the desired quantity of water by volume as compared to weight. Moreover, the numerical value of a given quantity of water in terms of volume (in liters) and weight (in kilogram) is same, as the density of water is one kilogram per litre. For example, for the concrete mix of water cement ratio 0.6 the quantity of water for one bag cement (i.e. 50 kg) will be 0.6 × 50 = 30 kg or 30 litres.

The batching of water by volume can be done by using the graduated buckets (in terms of litres). Appropriate care must be taken to avoid the spillage of water during mixing. Some of the mixers are fitted with water tanks and the required quantity of water, to be mixed with mix, can be controlled manually or automatically. Sometimes, water is added to the mix through a water supply line fitted with the water-meters to measure the exact quantity of water.

It is necessary to make adjustment for the free moisture content of aggregates in determining the quantity of water to be mixed as mix design is carried out assuming the aggregates in saturated surface dry (SSD) condition. In case, the aggregates have free moisture content (i.e. water is in excess of that required for SSD condition) then accordingly the reduced quantity of water should be mixed. On the contrary, if the aggregates are in dry state then additional quantity of water, which is required to bring these aggregates in SSD condition, should be mixed in excess.