Apparent ready mixed concrete shortages are caused by:
Miscalculation of form volume or slab thickness when actual dimensions exceed the assumed dimensions by even a fraction.
Deflection or distortion of the formwork.
Irregular subgrade and its settlement.
Smaller quantities wasted or used in incidental works for large pours.
To ensure sufficient supply of ready mixed concrete:
Measure formwork accurately and order sufficient quantity to finish the job.
For large pours, include an allowance of about 2% over planned dimensions to account for wastage, potential increased thickness, etc.
Towards the end of large pours, carefully measure the remaining volume and confirm the closing quantity to the ready mixed concrete supplier.
During winters: Depending on the workability, the ready mixed concrete might be usable for up to 3 hours.
During summers: In hot weather, ready mixed concrete may start stiffening within an hour, depending on the prevailing ambient temperature. If the ready mixed concrete dries faster, sprinkling with water or curing compounds is required to prevent the cracking of the plastic surface.
When the ready mixed concrete is transported to the construction site, the ready mixed concrete is pushed deeper into the drum attached to the back of the truck with the help of a spiral blade fitted within the drum. This is achieved by rotating the drum in one direction. This process is known as charging the transit mixer.
At the construction site, the drum is rotated in the other direction, which forces the ready mixed concrete out of the drum. This process is known as discharging. The ready mixed concrete may be discharged directly into chutes, pumps or on to conveyor belts.
Pumps are designed to facilitate pumping of ready mixed concrete through the pipeline under high hydraulic pressure. When ready mixed concrete is pushed through the pipeline, it is separated from pipe line wall by a lubricating layer of cement, water and fine aggregates. Ready mixed concrete should have enough cohesiveness and workability for the mix to move easily through pipeline, bends, reducers and hoses.