Concrete Poured after 90 minute limit 1

[DHKpeWI]

Concrete was poured at a shear wall at about 110 minutes. According to ASTM C-94, "The discharge of the concrete shall be completed within 1 ½ hours after the introduction of the mixing water to the cement and aggregates, or the introduction of the cement to the aggregates." Any thoguhts on how to proceed now that the pour has already happened? One thought I had was to request that core samples be taken and tested. The did not take cylinders of the concrete that was 110 minutes old.

 

[FlashSet]

Play hardball. Have the contractor remove the concrete in questions, and place new concrete.

 

[msquared48]

How highly was this wall loaded for the design?

Is it a super critical wall where the building would fail if it failed in shear, or are there others that were not poured at the same time im line with it that could pick up the load if it failed?

I would at least look at the answer to these questions, and perhaps some others, before you fire your loaded gun.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[Ron]

DHK...while you might have every contractual right to reject the concrete and that would be the appropriate measure, you also have to consider the practicality of such action. I agree that coring should be done. Since it is a shear wall, likely not exposed to any great degree, then durability is likely not an issue and the next step is to verify strength.

A 20-minute breach of the 90-minute criteria might not be an issue depending on environmental conditions and the mix design. Keep in mind that ASTM C94 has had the 90-minute criteria in it for many years, mostly based on a basic mix design with cement, aggregates and water. Admixtures can change this criterion.

There is no reason to remove good concrete. Evaluate the concrete. If good, leave in place...if not good remove.

 

[dik]

Establish a test criteria for coring before... Coring will not likely indicate anything is amiss. Great call...

Dik

 

[PilebuckEngineer]

Most state DOT's have the 90 minute rule, but do allow up to 120 minutes if a super plasticizer or high range water reducer is used. Usually, it just still needs to be within a temperature criteria, like less than 75-degrees. I wouldn't worry about the concrete. If it was tested as usual, met all the temperature, slump, and air specs I'd say it's good to go. Like it was mentioned before most of those specs are written for the lowest common denominator. For example, ACI sez you can't let concrete freefall more than 3', but I've freefalled up to 150' if it's the right mix. Also, coring won't help you much if this a wall (thin I assume < 12"). You'll know when the form is stripped if they got good consolidation or not.

 

[NS4U]

i had this happen once... we inspected the exterior of the concrete and did cores to make sure concrete was monolthic. we were able to convince ourselves the concrete was good and did not make the contractor remove and replace. in my case we made them take cylinders after 90 minutes.

the whole point of the 90 min. limit is to make sure the concrete doesn't set up during the placement. if you dont have cold joints in your concrete you may be able to convince yourself that you're ok, but it's going to require the contractor to do some destructive and maybe non-destructve testing on their own dime.

 

[concretemasonry]

The temperature of the concrete, strongly influences the aggregate is a major factor in the setting and curing of the concrete because it is commonly is stored outside or in unheated bins/bunkers. This only applies during the cooler months when the air temperature goes down or tries to rise. In very cold climates, larger concrete suppliers close down some plants to funnel the production through the plants with some heated storage and use heated mixing water or even inject steam into the mixer for preheating the mix before water is added.

It is not difficult or costly to check the temperature of the delivered concrete to determine weather effects on setting time. - Curing is a different story.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[JStephen]

Where the material was adequate for the purpose, but still substandard in some way, I've also heard of them making price adjustments to account for the difference between what they paid for and what they got.

 

[kylesito]

Making price adjustments isn't going to solve the issue if the concrete is somewhat deficient.

I second the idea of doing some in place testing and going from there.




PE, SE
Eastern United States

"If a builder builds a house for someone, and does not construct it properly, and the house which he built falls in and kills its owner, then that builder shall be put to death!"
~Code of Hammurabi

 

[aciinspector79]

Drill cores or shoot a probe.
AITA