effect of mixing time on concrete strength

[Hemifun]

Does anyone know of a widely recognized reference(ACI,PCA,etc.) that discusses the effect that prolonged mixing time has on concrete strength? I know most specs. limit mix time to about 1.5 hours but I believe this is primarily to avoid having to add additional water to maintain workability. I have a situation where a truck had to wait a longer than anticipated time due to problems with the pumper. After it became apparant that the pump was not going to work, the truck was sent to another site where the concrete was placed without the use of a pump. By this time more than 1.5 hours had elapsed. My question is, if no additional water was added to the mix, should this extended mixing time result in lower concrete strengths??

 

[phuduhudu]

I would think that the problem might be that the cement starts reacting and so you could get lower concrete strengths. I recall seeing something about this in Fulton's Concrete Technology.

Carl Bauer

http://www.bauerconsultbotswana.com

 

[MiketheEngineer]

Agreed and it might honeycomb(walls)even if vibrated or be very difficult to finish (slabs)

 

[civilperson]

Fineness modulus of the cement and the initial temperature are both factors in the initial set time, (as well as admixture retarders). Depending on the specific details, maybe or maybe not.

 

[SLTA]

is it possible to take a core sample and test it?