Quality Concrete and “Raising the Spec”

As our environment becomes more and more competitive, one thing that each licensee can do to “set itself apart” from the competition is to (a) raise the bar on quality and (b) get specifiers and customers to demand that higher level of quality. ReCon recognizes that with an increase in quality, some costs (materials costs, testing costs, etc.) may go up. At the same time, many of our ReCon Licensees are already delivering a measure of quality that is above the “minimum” that is set forth in the ReCon standard specification. Thus, why wouldn’t you want to promote it and take advantage of it. In addition, many of you have the capabilities to incrementally increase quality and / or the perception of quality without adding much to what you already are doing, so maybe you should consider doing it.

With that as a bit of background, what follows are some suggestions to consider:

  • Concrete Mix Design
  • Settle on a “standard ReCon mix design”.
  •  Must be 4000 psi…but if you are exceeding this in your mix design then specify it.
  • Must have air entrainment by volume of 5.5 to 8.5 percent.
  • Adopt a QA Plan that is specific to ReCon
  • ReCon can provide a template to follow.
  • The plan covers:
  • Plant Organization Chart
  • Plant Quality Control Organization Chart
  • Materials
  • Concrete Mix Design & Concrete Test Reports
  • Air Content
  • Slump
  • Temperature
  • Cylinders
  • Calibration
  • Production
  • Pre-pour Procedures
  • Casting Procedures
  • Post Pour Procedures
  • Date stamping blocks
  •  Plant Safety
  • Complete periodic freeze thaw testing on your “standard ReCon mix design”
  • The test to be completed to demonstrate excellent freeze thaw durability of wet cast concrete is ASTM C666 which will run your concrete sample through 300 freeze thaw cycles in water. It is specifically designed for WET CAST concrete.
  • Frequently we see specifiers call out freeze thaw requirements in “big block specs” that reference ASTM 1262 and ASTM 1372. These tests are designed for DRY CAST concrete (small retaining wall blocks) and generally the spec is written so that coupons are cut from block actually delivered to the site (and then tests are run with results coming back to the customer several months after the wall is already built)!   If you see this spec, you need to seek clarification from the spec writer (or inform them that quality for wet cast concrete comes from a QA Plan, a standard mix design, periodic compressive strength and air pot testing of the block during production, retention of mix design records, and date stamping of the block). We need to substitute ASTM 1262 and ASTM 1372 for your well documented QA procedures!
  •  Consider running an ASTM C666 Test on your standard ReCon mix design.
  • The test costs about $1200, so you only want to run it once every several years and you want to run it on a “set mix design”.
  • The test takes about 3 – 4 months to run…300 cycles over a 100 day period.
  • Special beams must be poured for this test…they are about 3” X 3” X 10”. They must be well vibrated or rodded when prepared.
  • Obviously, since the test is expensive and time consuming, you want to take all precautions in advance to make sure your mix design is adequate to pass and the preparation of the beam is proper. Passing the test is highly dependent on (a) having proper air entrainment in the mix (target 6 ½%), and (b) having durable quality aggregates.
  • You should call your aggregate supplier and ask them about the quality of the aggregates you are using and their ability to pass freeze thaw testing. They should be able to advise you on this.
  • You should run an airpot test on the concrete that you are using to create the beam to insure proper air content in the mix being used.
  • Most labs will check the density of the concrete on a weekly basis during the 100 day test cycle. If you fall below the durability standards, they will stop the test and will charge you only for the number of cycles completed. You may want to ask your lab if they offer this in their fee schedule.
  • If you don’t want to spend the money on ASTM C666, then consider having a lab perform a “hardened air void test” on a sample of your concrete mix. This test will cost about $500 and is an excellent predictor of the durability of concrete. It basically X-rays the concrete and can determine the distribution of both entrained and entrapped air content. If the lab will accompany the report with a written statement that “based upon the test, the concrete should meet most standard freeze thaw durability requirements”, then you have some additional assurance of quality and durability that you can share with specifiers / customers.
  • Professional Certification
  • If you have a quality certification from your trade organization (i.e., ACI, NPCA, ACPA, PCI, CSI, or NRMCA), call it to the attention of the specifier.
  • DOT Approval
  • If you are an approved DOT producer of concrete products (even if ReCon is not DOT approved at this time in your state / province), call it to the attention of the specifier.

In summary, you should raise the bar to the level that you currently are at and you should consider raising the bar even higher if you think it will weed out some of the competition. When you call on a customer or specifier, you should leave at their office the ReCon Brochure, the ReCon Design Manual, your standard mix design, a copy of your C666 test results (or hardened air void report), a copy of the Federal Highway Administration Report on the importance of wet-cast air entrained concrete in retaining wall blocks used in freeze thaw / road salt environment, and a summary of your producer qualifications (DOT approved, QA Plan in place, NPCA certified, etc.)

Please feel free to call with questions or comments. There may be multiple choices for retaining wall products, but there is only ONE of YOU in your market. Make sure your customer knows how good you really are!

Stan Hamilton

President

ReCon Wall Systems, Inc.