Effect of time delay after mixing on rheological properties of self-compacting concrete

Abstract EN

Self-compacting concrete (SCC) has been described as "the most revolutionary development in concrete construction for several decades".

The present work gives attention to an effect, which can affect the rheological performance of an SCC mix adversely, and hence, its hardened properties also.

This effect is the 'time delay' or the time elapsed since the end of the mixing process and the start of the placement of concrete process (or even its end) in situ.

An eight SCC mixes were made in this study, in which three values of this time delay were considered : 0, 15 and 30 minutes, and tests were applied on SCC mixes without and with a retarding admixture.

The slump flow, V-funnel and L-box tests were applied for the rheological properties and the compressive and splitting tensile strength tests at 7, 28 and 56 days were carried out for the strength properties of the SCC mixes used.

Results showed that a gradual decrease in the rheological properties of the SCC mix occurred as the time delay after mixing increased.

At 30 minutes time delay some of the SCC limits were not satisfied.

However, the addition of 0.5 % retarding admixture to the SCC mix could attain the rheological properties of the mix within the SCC limits even at 30 minutes time delay.