The purpose of curing is to reduce the rate of heat loss of freshly placed concrete to the atmosphere and to minimize the temperature gradient across concrete cross section.
Moreover, curing serves to reduce of the loss water from freshly placed concrete to the atmosphere.
Ponding: This method of thermal curing is readily affected by weather condition (cold wind).
Moreover, a large amount of water used has to be disposed off the construction sites after curing.
Polythene sheet: This method of curing is based on the principle that there is no flow of air over the concrete surface and thereby no evaporation can take place on top of the freshly concreted surface by provision of polythene sheets.
However, it suffers from the demerit that polythene sheets can be easily blown off in windy condition and the performance of curing would be affected.
Moreover, for water lost due to self-desiccation, this method cannot replenish these losses.