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 .