Segregation - fresh concrete
Segregation - fresh concrete
(OP)
ACI 301 and other spec guides talk about segregation, but the discussion seems very subjective.
What hard tools does the inspector have to accept or reject ready-mix concrete based on segregation.
My question comes from concern about a project where fresh concrete will be transported in a 1-yard bucket about 25 minutes up a rough-terrain road using a forward-reach forklift ("GradAll")?
What hard tools does the inspector have to accept or reject ready-mix concrete based on segregation.
My question comes from concern about a project where fresh concrete will be transported in a 1-yard bucket about 25 minutes up a rough-terrain road using a forward-reach forklift ("GradAll")?





RE: Segregation - fresh concrete
Segregation of the concrete is applied to when the inspector sees the concrete and not on suspected problems that might be encountered later.
If it is a bid document, cover all the bases.
That is why the code is cannot address all possibilities.
Dick
RE: Segregation - fresh concrete
I would also expect that your issue might be more of lack of consolidation, rather than segregation.
RE: Segregation - fresh concrete
Also, a retardant such as Pozzolith or Daratard will be used, and the concrete will be vibrated.
I've seen segregated concrete before, but don't know if simple re-mixing will "fix" this, and need adequate backing before I reject a mix.
RE: Segregation - fresh concrete
RE: Segregation - fresh concrete
Dik
RE: Segregation - fresh concrete
RE: Segregation - fresh concrete
Concrete with a 4-inch slump can segregate, as can concrete with a 2-inch slump and an 8-inch slump. Just because you haven't seen it happen, doesn't mean that it can't happen.
RE: Segregation - fresh concrete
Thanks for the discussion.
One last question: Is there a recognized standard for calling fresh concrete "segregated?" That is, if you're physically at the site during concreting, what criteria would you use before you could say with confidence - "I will not accept this concrete since it is no longer homogeneous..." Besides risking your life at the hands of an angry mob, the engineer has to have some criteria.
I have seen localized segregation from over-vibrated concrete (usually at the top of a wall), but wouldn't know how to measure that, or put numbers to it.
RE: Segregation - fresh concrete
Dik
RE: Segregation - fresh concrete
RE: Segregation - fresh concrete
RE: Segregation - fresh concrete
Greg
RE: Segregation - fresh concrete
http://www.todaysconcretetechnology.com/forum/
RE: Segregation - fresh concrete
by my count, at best you can order a 2 yrd truck. Segregation shouldn't be a problem, but all concern for which can be cured with a well-graded mix.
Here are some other issues to consider.
If they get two trips per truck, how will the old concrete in the pump line affect overall quality... maybe they will dose it with some water to keep it fluid. Maybe the truck will dose between pours because he has been sitting there spinning for a long time... Will they try to work on wet days and possibly damage this access way. Will weather, truck arrival, or equipment failures affect the delivery so that the contractor will feel obliged to place old concrete because its better than having a monster cold joint.
Also, it has been my experience that truck drivers just destroy concrete when they add water to a small load.