What are the reasons for not setting of concrete after 24 Hours?

There are two main reasons for not setting of concrete after 24 Hours: –

1. Concrete releases moisture from their surface as it dries. But if there is high moisture in the air, also known as high humidity. The moisture from the concrete would slow evaporate. So, too much moisture in the air will slow down the drying process of concrete.
2. The same case in cooler weather. If the air temperature is too cold, then the concrete curing process will slow down or stop altogether. Concrete to cure properly needs to stay warm, so cold damp weather conditions will slow down the curing and drying process.