Overcoming the slump loss of fresh self compacting concrete by overdosing technique for different transportation times

Slump loss is a common phenomenon at the job sites because it results from gradual stiffening and setting of hydrated portland cement paste, which is associated with the formation of hydration products such as ettringite and the calcium silicate hydrate. In the present investigation a study had been undertaken to study the effectiveness of overdosing the chemical admixture which was used to provide the initial optimum admixture dosages resulting in suitable self compacting concrete (SCC) for different transportation times. A suitable SCC was designed for a slump flow of 680mm with very high stability. Five different transportation times such as 10, 30, 60, 90 and 120 minutes were used. The test results indicated that the selected overdosing method was successful in producing SCCs with a similar unconfined flowability, stability and passing ability to those obtained at the control transportation time of 10 minutes