How should a concrete mix water added on site? 1

[abusementpark]

How long should a concrete truck mix water that is added on site?

I know it isn't a good practice at all, but it happens. Any ideas on the minimum amount of time it should mix after the water is added before it is poured? Does ACI comment on this matter?

 

[dik]

Only at the direction of the concrete mix supplier...

Dik

 

[Ron]

abusementpark....it is more related to the number of revolutions of the drum. When you add water at the site, it should be mixed with an additional 50 to 60 drum revolutions at mixing speed, assuming the drums and augers are in good condition.

The truck should have a working revolution counter and a readable site glass or water meter to check the volume of water introduced into the mix.

The total revolutions of the drum at discharge should be less than 300, including initial mixing, transit mixing and site mixing.

 

[Drumchaser]

agree with Ron and would add: an important factor in the quality of the concrete is how much water was withheld at the plant, based on the mix design, allowing how much water can be added at the site. Never a good idea to add more water than the mix design allows. Potential for costly further strength testing if specimens fail, ie. coring, structural analysis.

Concrete truck (agitated drum mixer) recommendations for mixing speed, max volume of drum, agitating speed etc. are noted on a plate displayed on the exterior of the truck, usually in plain site unless you have something outdated/non-standard.

And yes I am confident ACI and ASTM test methods reg.s include an abundance of reg.s relating to these matters, if you have access and time to interpret the text.

 

[Ron]

Yes, as Drumchaser noted, ASTM C94 covers most of these issues. dik is exactly right...don't give the ready mix supplier an easy out...make their QC guy do the water addition and as DC noted...within the parameters of the mix design.

 

[kieran1]

Definitely agree with Dik on this

Kieran