High Volume Fly Ash - SCC Concrete

[BigH]

Another concrete question. Contractor is proposing the use of 30MPa self compacting concrete using very high fly ash (about 70%) content. Has anyone had any experience with such high levels of fly ash - and for SCC? Any case histories; data, etc. This is for placing beneath a spiral tube in a powerhouse - which you can imagine has very stringent tolerance levels.

As one may surmise - we have myriads of concrete problems - mainly due to contractor and very low maximum temperatures.

Thanks.

 

[oldestguy]

All I can say is there are different fly ashes and some have very little Calcium Oxide, while those from US western mines generally have about 30 percent Calcium Oxide and that stuff (by itself) sets up real hard and fast. Lots of heat generated also.

 

[Ron]

BigH...expect very slow strength gain. Wouldn't accept unless they have moving average strength data and a strength gain curve for that particular mix design. 70% is awfully high....normally no more than 1/2 that amount.

 

[BigH]

oldestguy - our CaO is 10-11%.

Ron: We've been using 50-50 with good results on strength. We are using strength at 90 days rather than at 28 days as criteria. Will try to put together something to show you. 70% is high - this is for under spiralcase - we'll need to grout as well.

Sorry about not answering yesterday - I'm not getting the green stars showing new posts.