The Concrete Producer: Problem Clinic

Aggregate Moisture in Concrete

Thu, 13 Jun 2013 04:34:16 EST

The moisture condition of aggregate in concrete is very important. The absorption of the aggregate indicates the quantity of water which will be absorbed into the pore structure.

Preventing Slump Loss

Wed, 10 Apr 2013 05:58:44 EST

Many things can cause rapid slump loss. Aggregate, cement chemistry, fly ash sources, and admixtures are culprits.

RoMix + RO-396

Wed, 27 Mar 2013 03:13:27 EST

RO-396 High Performance Form Release Agent exceeds all VOC regulations and is easy to apply.

Coming Up Short

Thu, 10 Jan 2013 01:04:00 EST

QUESTION: We have a project where the contractor is constantly complaining we are shorting them on concrete. We have checked yield several times during placements and came up with good results. What should we do next?

It's About Time

Fri, 11 Jan 2013 09:45:42 EST

We are constantly battling time constrains on ready-mix deliveries and need help extending the time limits on some projects. We can maintain slump with water reducers easily beyond the 60 or 90 minutes allowed in the specifications. What advice can you offer?

Your Concrete's Air Content

Fri, 11 Jan 2013 09:45:25 EST

Out of Plumb Precast Panels

Wed, 9 Jan 2013 12:30:20 EST

Quality's Costs

Thu, 13 Dec 2012 02:58:41 EST

Q: I'm a quality control manager for a mid-size ready-mix producer and am dealing with several quality issues which need resolution. I am having difficulties convincing the owner that he needs to increase funding for the quality system in order to produce more consistent concrete. How can I convince him?

Working With Your Lab

Mon, 14 Jan 2013 03:13:57 EST

Q: We are experiencing low compressive strength test results on some concrete we supplied to a job. We know it is due to poor testing of the cylinders. How do we convince the contractor and engineer where the issue is?

Testing for Air in Concrete

Mon, 14 Jan 2013 03:15:45 EST

We retrieved a piece of the material and an air-void analysis showed that the air content met the project spec. What happened?

Is Your Aggregate Alkali-Silica Reactive?

Mon, 14 Jan 2013 03:16:50 EST

Q: We received a request to submit proof that our aggregates are not alkali-silica reactive. We've never seen this type of request before in our area. They required ASTM C1260 testing, which we completed and failed. What do we do now?

Tread Lightly When Going Green

Mon, 17 Dec 2012 02:00:28 EST

Q: We operate in an area that does not have many LEED projects. However, we are now seeing more such projects under development, and specifications requiring LEED submittals are becoming more frequent. How can we manufacture concrete to meet these requirements, and how can we make our concrete more sustainable?

Making a Quality Hire

Mon, 17 Dec 2012 02:15:10 EST

Q: We are a small but growing ready-mix producer. We have just decided to open a portable plant to service a multiyear project. We are considering hiring a full-time quality control manager. At what annual production volume does it make sense to make this hire?

Lightweight Block As An Alternative

Mon, 14 Jan 2013 03:18:24 EST

Q: We are working on a project where the owner is trying to earn LEED credits. So we are trying to convince the structural engineer to use lightweight block. How can we get him to use lightweight block as an alternative?

Do Fibers Affect Concrete's Workability?

Mon, 17 Dec 2012 01:49:15 EST

Q: We will be supplying ready mixed concrete for a commercial floor project. The engineer of record has added fibers to the project specification. The concrete contractor is now concerned that with this job change, the fibers may slow his placement procedures and has submitted a change order request to place and finish the fiber concrete mix.Does adding fibers affect the workability of a concrete mix? Do synthetic and steel fibers affect slump?

Wall Ties and Wind Load

Mon, 14 Jan 2013 03:20:34 EST

Q: If the purpose of these ties is to support the veneer during winds, why does it make any difference what backup is used?

Working With Controlled Low-Strength Materials

Mon, 17 Dec 2012 01:47:51 EST

We are about to bid on a project calling for controlled low-strength materials (CLSM) for backfilling sewers and other underground utilities. The designer is hoping to use this material to earn LEED credits. We have been asked to verify the density of CLSM we plan to provide. Does CLSM's density in place vary? Why is this important to the design engineer? And how can we control the density?

Can a Contractor Add Fibers?

Mon, 14 Jan 2013 03:22:09 EST

QUESTION: We recently worked with a new customer, and the concrete contractor's owner arrived on the jobsite just as the pour was about to start. He unloaded several boxes containing pre-weighed packages of synthetic fibers.

Problem Clinic

Mon, 14 Jan 2013 03:26:47 EST

How Long Can a Ready-mix Truck Wait?

Mon, 14 Jan 2013 03:28:29 EST

We were all set to start when the testing lab's field tech stopped the pour. He said the concrete was too old and he had no option but to reject all of the loads. Was the testing lab's field rep correct in rejecting the loads? Was there an alternative?