Designing the future: creating new mix designs for ICFs: you are invited to participate in the...

Market acceptance of insulating concrete forms (ICF) construction among contractors and consumers has steadily increased over the past few years. According to figures compiled by the Portland Cement Association and the National Association of Home Builders, 2.7% of all new above-grade homes

Producers have played a key part in this tremendous growth. Promotion councils in almost every major city have constructed demonstration ICF structures. Many other producers have contributed forms and ready-mixed concrete to local chapters of Habitat for Humanity. And one Minnesota producer has even started to brand a regional approach to ICF construction.

All this said, one aspect of ICF construction hasn't shared in the marketing spotlight. Producers have not demonstrated to engineers and designers how performance-based ready-mixed concrete can lower the cost of ICF construction. While there has been a great deal of research on the building structure as it pertains to construction codes, not much has been done on the question of ICF mix performance designs.

What do contractors want in a performance-based ICF mix design? Fresh concrete needs to be pumpable. When placed in the forms, the mix must have high flowability to fill all the voids easily, quickly, and without too much excess water. Concrete must exhibit residual strength. Just as important, the mix's delivered price needs to be economical so that the ICF constructor can compete against the traditional frame builder.

A chance to get involved

To help meet these challenges, THE CONCRETE PRODUCER is coordinating a research project with Aggregate Research Industries (ARI) to develop guidelines for performance-based ICF mix design. Joining us as the cement sponsor in this important endeavor is Lafarge Corp. According to Bruce Blair, Lafarge's vice president for cements, concrete producers must work together to convince code agencies and engineers of the need to specify perfomance-based mix designs.

"We see our involvement in this research effort as a first step in developing the data needed to support the use of performance-based mixes," said Blair.

Currently, a 2500-psi mix is the typical specification for concrete used to fill the voids in ICFs. Because there are few published guidelines on the properties of this mix other than strength, producers often supply standard mixes for ICF--the same mixes used for foundation walls, sidewalks, and driveways.

There are some problems with this approach. Often these mixes are too harsh (rocky) for the contractor to place efficiently. Producers often use the same ingredients in the ICF mix as they do for other concrete applications, so they charge the same price even though the final design requirements aren't as severe. And as ICF construction often represents a small percentage of a producer's annual production, it's hard to justify a great deal of lab or mix design expense to create custom mixes.

The research effort supported by THE CONCRETE PRODUCER challenges producers to come up with a range of special ICF mixes. Producers are being asked not only to design mixes that achieve the necessary strength requirements, but combine a wide range of ingredients that will produce a more economical mix. By organizing a group of sponsors and encouraging industry-wide competition, we will draw on the best and most creative minds in the concrete mix design business.

This is more than a contest, however. All of this important mix design research will be directed by Barry Hudson and his ARI research staff. Hudson, chief investigator at the Richmond, Va.-based consulting laboratory, will use the data to develop a research document that will help producers, design engineers, and code officials understand ICF mix designs. Hudson hopes this research also will encourage producers to develop customized mixes using ingredients not normally considered for such applications.

Key to Hudson's research will be the collection of various mix designs along with their tested qualities. All cylinders will be cast using Lafarge cement and aggregates produced by Luck Stone locations. Producers will be asked to submit a ICF mix design that is economical, attains 2500 psi alter 28 days, and exhibits good flowability and mix stability. In addition, and here's where the fun begins, the mix must exhibit a strong fiber pullout index.

Benefits to the industry

According to Hudson, with the proposed introduction of a new code draft, currently in committee at the Strategic Development Council, there is a strong possibility that ICFs will no longer need steel reinforcing when placing concrete hatched with synthetic fibers. He foresees a number of benefits to the concrete industry arising from this cooperative research project.

For one thing, Hudson views this combined effort as an important financial contribution to the industry. "To accomplish a research effort of this magnitude on our own, we'd have to charge the sponsoring partner a great deal of money," he said. "But with the support of our sponsors and entrants, ARI and THE CONCRETE PRODUCER will provide the concrete industry an economical and effective way to participate in needed practical research."

Hudson added that the project may help increase communication between producers and their suppliers. "This is a rare opportunity for admixture companies, quarries, supplementary cement suppliers, and fiber manufacturers to work with their customers in a manner that yields fair and unbiased test results," he said.

The involvement of THE CONCRETE PRODUCER reinforces Hanley-Wood's commitment to the industry. "For years our editorial staff has participated in a number of very practical research projects with applications that can be quickly instituted in the field," said Patrick Carroll, group publisher. "We hope that a strong reader involvement will allow us to continue this effort in the future with mix contests focused on chloride permeability and the use of recycled water."

ARI has created a special Web site at www.aggregateresearch.com/site/mix-design where interested producers can find details and acquire an entry form. ARI is administering the contest, so all questions should be directed to Barry Hudson, 804-690-7166, e-mail bhudson@aggregatereserach.com.

Prizes

A grand prize will be awarded to the mix design submittal that achieves the highest composite score based upon the four categories. The winning testing lab will also be featured in the July issue of THE CONCRETE PRODUCER.

Additional prizes will be given to the first, second, and third places in each of the five judging categories. Certificates of honor will go to the producers who make it to the second round of testing.

General Contest Rules and Guidelines

The Designing the Future contest will include two testing rounds. In the first round all submittals will be tested. Entrants will receive a number that identifies their submission and the test results will be posted on a page at ARI's Web site. The entry period for the first round runs through March 1, 2003.

To make it to the second round, the mix design must be ranked in the top 10% of all submittals as of April 1. Entrants into this second tier will be allowed to make adjustments to their mix submittals. The adjusted mix designs will be cast by April 15, with the final breaks occurring mid-May.

A mix must he designed so that it can be easily reproduced in standard concrete operations. The laboratory testing will follow ASTM C-33. All design submittals must yield correctly once batched.

Multiple mix designs will not be accepted and entries will be recorded on a first-come, first-mixed basis. ARI representatives will make the final judgment as to whether a submittal is a multiple sample.

Entrants will be limited to a mix design using ingredients supplied by contest sponsors. Luck Stone has agreed to provide all materials for the research project. ARI will select eight different coarse aggregates and six sands (three natural and three manufactured). Test reports providing information on all physical characterizations including gradings, voids, organic impurities and flow times density, absorption, and unit weight will be posted on the ARI Web site. Entrants may also purchase sample quantities for a nominal fee.

Entrants will receive a chart that lists the standardized costs of materials. Mix design rankings will be based upon the following factors:

30% Closest to the design strength based on the average strength of 2500 psi

30% Most economical mix

15% Highest residual strength based upon ASTM 1299 test method

25% Workability

Entrants will be limited to producers, testing labs, and industry consultants.

The entry fee is $250 per submittal made payable to Hanley-Wood, LLC, and there is no limit on submittals by a lab or producer. Entry submittals will be sent first to THE CONCRETE PRODUCER and then forwarded to ARI for testing with only a lab sample number. The entrant will receive the number when it is determined that the submittal is unique.

ARI will test all samples. Failure to achieve a compressive strength of at least 2500 psi will disqualify the sample.

Each submittal will receive a complimentary report listing all mix designs and test results at the end of the review process. The retail value of this extensive report will be $500.

Application forms are available at www.aggregate research.com/site/mixdesign or by contacting Amara Rozgus at arozgus@hanley-wood.com. Entry materials will not be returned. Application materials should be mailed to:

2003 Mix Contest

THE CONCRETE PRODUCER

426 S. Westgate St.

Addison IL 60101 USA