Design Mix :

At most of the places the ingredients for making concrete, viz. cement, sand, aggregates & water, are added by volume. This method is called volumetric batching. The mode of measurement for these materials is basket or tasla, etc. No two ingredients are measured with the same measuring instrument. As a result of this the volume of materials as desired, is never maintained. Also there is no measuring instrument for water. Water is always added by approximation. In this way we never get same strength in two batches that are prepared at the site. The quality of materials that are used is never taken into consideration. This seriously affects not only the strength of concrete but also its Durability. Extra water added makes concrete porous, thus making the structure to leak & steel corrode. Neither the raw materials nor the concrete produced is checked for its quality at site. Hence all these factors lead to making of bad concrete & ultimately a bad quality structure. Looking to the above factors, the best way is to design the mix of concrete. In designing the mix, the quality of raw materials are checked thoroughly as per the BIS norms. The mix is designed, for the required strength of concrete on weighing basis. That is for a given strength of concrete, the weight of individual material (including water) is calculated for one cubic meter of volume of concrete. This mix is then prepared at site / batching plant by weighing each item individually. This is done strictly as per norms laid by BIS. This method takes care of Strength & Durability of concrete. At CRSons RMC, all the ingredients are weighed by automatic computerized machines. These machines are regularly checked for their accuracy. The accuracy level is +- 0.5% for these machines. The mix is mixed in a highly sophisticated mixer, operated thru computer. This mixer gives a homogeneous & cohesive mix as desired. The water cement ratio is very well taken care of in this method of mixing. Even if there is any extra moisture in sand or aggregates, the computer automatically adjusts the water quantity in the concrete mix, so as to maintain exact w/c ratio.