How the distance between the Plant and the Site matters?
We have seen few customers uncomfortable with the concept of Ready Mix Concrete though it is a widely proven standard to give precise product compared to regular hand mix. We know how much those customers are losing-out in terms of handling the whole complexities at the construction site rather than simply procuring ready Mix Concrete. But on the other side of the equation, we also know the fears of the builders which are faced by the market and their previous history. The problem boils down to bad concrete quality even though they procured from RMC plant. The complains were as common as improper water content to as bad as concrete not setting for days together which is a debacle. This newsletter shows the relation between the concrete quality and the plant-to-site distance.
The choice made by buyer for supplier finalization has to be done very carefully by giving enough importance to the distance between the plant and the site. Most of the times, Builders choose suppliers just based on the price quotation. When the distance between the plant and the site is very far and considering the traffic conditions of the Tier-1 cities in India, the probability of getting good mix comes down significantly. The following properties of concrete gets affected due to long haul.
1. Workability: Due to excess time taken for transportation, the water content will get decreased because of evaporation, absorption by aggregates and hydration reaction between water and cement. This less workability will lead to many imperfections like pumping problems, segregation, etc.
This problem can be sorted our by measuring the slump for every vehicle. Generally suppliers address this problem to make sure the pumping goes well. However it is advisable to have a resource to make sure this issue is not triggered.
2. Setting of Concrete: When the transit time is high, initial setting of concrete takes place which is not an ideal thing to happen. Using plasticizers(retarders) is the obvious solution for this situation. But this is the case where the market has seen the worse cases. Improper usage of retarders can prolong the setting of concrete to more than the desired time or sometimes the concrete doesn’t set at all.
3. Transit Time: In order to maintain the workability and setting of concrete, the concrete should be delivered completely to the site within 90 mins (when the atmospheric temperature is above 200C) and within two hours ( when the atmospheric temperature is at or below 200C)of adding the mixing water to the dry mix of cement and aggregate or adding the cement to the aggregate whichever is earlier. This is very tough in the cases where the batching plant is very far away.
So in order to address all the problems, there is one single and simple remedy. It is always better to have the plant nearby. Builders shouldn’t get tempted for the minimum rates quoted by the suppliers who are far away yet quotes very handy price. This practice keeps the whole concrete quality at stake.
Refer the below link for detailed technical understanding from which the above article is partially based on: https://theconstructor.org/concrete/effect-of-transit-time-on-ready-mix-concrete/8754/amp
