Myth / Fact
How often have you carried a fact along with you and even shared it with others also and at last you realize it was a Myth? Have you ever heard of the Fact that‘ Great wall of China’ is visible from space? Well it is a myth. No man made structure is visible from space. Funny is not it? Likewise in our construction industry we have been carrying so many myths that may be busted whenever a learned engineer confront us.
MYTH: Water could be added to concrete to make it more workable for a prolonged period
Fact: Adding water later to the mix will increase its w / c ratio thus lowering its strength.
So many times we have seen that labors keep sprinkling water on concrete to delay its setting and keep the concrete workable. Many specifications forbid any onsite addition of water. Even so, there are other ways to increase the slump and workability of concrete. The cement in concrete mix needs water to hydrate and form Calcium-Silicate-Hydrate( CSH) which is glue that holds the concrete together. The water is chemically bound during the reaction with cement. However not all the water is needed for C-S-H formation and other hydration products. There is additional water that becomes physically bound between the cement hydrates.
The cement in concrete mix needs water to hydrate and form Calcium-Silicate-Hydrate( CSH) which is glue that holds the concrete together. The water is chemically bound during the reaction with cement. However not all the water is needed for C-S-H formation and other hydration products. There is additional water that becomes physically bound between the cement hydrates.
There are other ways to increased slump and workability of concrete. Aggregate gradation and the maximum size of the aggregate both greatly influence cement and water requirements, which affect mix workability. Water reducers and super plasticizers can also be used to increase the slump while maintaining the water-to-cement ratio. And air-entrainment can increase workability. Adding water to a mix that contains chemical admixtures will change the properties of the mix and can cause excessive slump loss, inconsistent setting, and changes in air content.