Mohammed you have asked a simular question without the High strength part and you have asked the Cube question in high strength concrete, This is what we have done done for a commersial use of High strength fiber reinforced concrete only 50 mm thick slabs. Design strength was 100 Mpa MOR required was 10 Mpa and then enegy under the curve calculated to 25 mm deformation was 1000 joules. The mix design included Cem I 52,5N cement, Fly Ash and Silica Fume (microsilica) We used pure graded silica sand with the max size of 2.36 mm and 6.7 mm aggregate and we used 100 kg of 30 x 0.45 mm fibres two admixtures, ap PCE superplastisizer at about 2 % and a PCE retarder at about 1% . The control in the field was with 100 mm cubes 100 mm beams and 600 x 50 mm cncrete disks. We got up to 130 mpa but unfortunately also as low as 80 Mpa because of "Air entraining" in the concrete caused by a Grinding aid used by the Cement manufacturer. We then also add an antifoamer, to make sure the mix design work on site when transported in a readymix truck in peak hours and still with fibres, gives a Flow of 550 mm when arrive on site. This was only possible with the retarder AND the super. For the retarder alone to give us that workability we had to overdose leading to very retard setting on site, that was our reason. So I don't know your reason for the question but this should give you hopefully a direction.
Regards Derek Mostert (MICT)
Derek Mostert . Thanks alot for your clarification, actually i am working on high performance concrete and i faced fast setting time (40 min for the initial setting time) Thats why i want acceptable setting time for finishing the casting proparly. I will try to use (fixed superplasticizer percentage with different percent of retarders and i will check the workability and setting time)
Best regards
Set retarder is not necessary. I have used high range water reducing admixture that can substitute water up to 40% without using set retarder in UHPC mixtures.
Srinivas Allena . How could i increase the setting time as i suffered from rapid setting time.
Thanks for your interesting
By using a set retarder! What is the problem why cant you use both, as long as the admixtures are compatible use both, There are already blended admixtures with both properties available too. I think you should first do a bit of homework on the admixture side, because it would not be professional from us to give admix company names and admixture names in this forum.
Regards Derek
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