Testing Procedures for a 10" Slump at a Pre-Stress Plant

[brucein]

I'm a bit of a Jack of all trades and I have been recently tasked to provide inspection at a Pre-Stress Plant making concrete I-Girders. The powers before me have allowed the Slump, after adding Super Plasticizer, to be at 10 inches. The water to cement ratio's are well within the mix design requirements although the Super P is on the high side.

I have read thread167-227472 on slump, and it was very useful for some issues. Here is my question:

The slump cone (for Missouri at least)is only good up to 9 inches. 10" doesn't really meet the flowable or SCC relm, or does it. What is a good way to ensure workability/fluidity and uniformity of my mix.

Another concern: The beams make the designed final strength within 12 to 24 hours. Is there a concern of the beam's being brittle?

 

[TXStructural]

Slump only tells you about the consistency from batch to batch. If they insist on the test, then consider inverting the cone on a flat, level board and measuring the diameter of the resultant puddle. This will tell you more than slump. You can check for the depth of the resultant blob, and can check the edge of the flow for segregation.

The high cementitious materials content required for such rapid development of high strengths will typically result in brittle performance, but that is expected.

If they are using a polycarboxylate HRWA rather than an old-style super-P, you should get good cohesion and viscosity, with little to no segregation. This may also help reduce cement and increase aggregate, while maintaining consolidation and assuring suspension of large aggregate. Be sure there is sufficient water in the mix to hydrate all of the cementitious materials without excess.