Question
What are the main drawbacks of curing by ponding and polythene sheets?

Answer
Purpose of curing is to decrease the speed of heat loss of freshly placed concrete to atmosphere and to reduce temperature gradient across concrete cross section. Furthermore, curing serves to cut of loss water from freshly placed concrete to atmosphere.

Ponding- This means of thermal curing is readily affected by weather condition as cold wind. Furthermore, a large quantity of water used has to be disposed off construction sites after curing.

Polythene sheet- This process of curing is based on principle that there is no flow of air over concrete surface and thereby no evaporation can take place on top of freshly concreted surface by provision of polythene sheets. Though, it suffers from demerit that polythene sheets are able to be easily blown off in windy condition and presentation of curing will be affected. Furthermore, for water lost due to self-desiccation, this way cannot replenish these losses.