Concrete Canoes: Lightweight Competition Aggregate and Pozz

HESS PUMICE

concrete canoe: lightweight competition aggregate

A seemingly incongruous engineering feat, a tapestry woven by various disciplines, an experience in team building, all bound in unforgettable: the concrete canoe.

Sourcing Our Pumice

Sourcing our pumice aggregate and pozzolans for your competition boat is a two-step process.

1) MIX DESIGN / LAB SAMPLES: Competition teams typically start with small testing samples to zero in on the right concrete mix design. Directly order the testing samples you want to work with and get them on the way. The grades you see available to order are the typical grades (including pozzolan) requested over the years.

2) CANOE CONSTRUCTION SAND, AGGREGATE AND POZZOLAN: When you’re ready to order the pumice pozz and aggregate, send an email to our Fulfillment Center at fc@hesspumice.com and tell us which grade(s) and how much you need. We are logistics experts: we’ll use all of our resources to get you the best freight rate. Be sure and include all of the information below in your email request.

EMAIL REQUEST INFORMATION
Your Name + Team Name
Your Contact Information (cell and email)
Your University/College/School
Pumice Grade(s) wanted and Quantity of each
Physical Shipping Address (accessible by LTL truck)

RECOMMENDED PUMICE GRADES

Our small aggregate offerings. Grade photos and grade range tech data sheets (TDS) are linked from the grade order blocks on the ORDER PAGE.

TIGHT GRADES

Narrow-range graded pumice sand and small aggregate. Grade sizes: #2, #5, #7, #10, and a mine grade, 3/8x#8MN. These grades are used by teams looking for precise control of the aggregate size blend (including the fines).

WIDE GRADES

These two aggregate mine grades are screened to grade for top size only and not dried. They include a wider range of particle sizes in the grade range, including extensive fines (sand). Grades include 3/8FinesMN and 1/8FinesMN.

PUMICE POZZOLAN

Standard Pozz (DS325 - 25 micron APS) and UltraPozz (3 microns APS) grades.

ORDER ONLINE

Order pumice aggregate and pozzolan testing samples directly from the Hess Fulfillment Center via the site Pumice Store.

Working with Pumice Concrete

Preparing and handling lighter pumice concrete is similar to handling normal-weight (heavy) concrete, with a few key differences, as detailed below.

LIGHTWEIGHT AGGREGATES NEED A POZZOLAN

It’s one of concrete science’s ironic truths: lightweight aggregates are reactive, and if used with ordinary Portland cement without the mitigating effects of a reactive pozzolan, the concrete inevitably develops a nasty ASR problem—a reaction between the high silica content in the aggregate and the alkali in the hydrated cement paste. The alkali-silica reaction forms expansive gels that generate a sort of slow-motion explosion, map-cracking and eventually destroying concrete structures from the inside out.

Adding a high-quality pozzolan—and here’s where the irony lies—made from the same pumice as the aggregate, but milled to a fine powder, ignites an immediate (secondary) reaction within the hydrated lime paste, consuming the deleterious calcium hydroxide (CH) generated by the primary cementitious reaction. Without that CH, there’s no fuel to trigger ASR.

Pozzolan is defined in ACI 116R as: “…a siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties.”

Learn more about natural pozzolans at the National Pozzolan Association and Hess Pozz websites. Also download the whitepapers: Flatline Alkali-Silica Reaction with Pumice-Blended Cement and how Pumice Pozzolans Super-Charge Concrete performance.

MIXING AND PLACING PUMICE CONCRETE

PREWETTING. All pumice aggregate should be uniformly prewet to reach total saturation, then be allowed to sit while excess water drains out. This will fill the internal voids of the pumice with water. As dry pumice aggregate will aggressively absorb mix water, prewetting the mix will prevent its drying before placement and slump will be uniform throughout the load, and from load to load.

SLUMP. Pumice concrete has about two inches less slump than heavy concrete for the same consistency and workability. Low-slump pumice concrete will flow when vibrated, and finishers can get on it much sooner when the slump is held to two-to-three inches.

AVOID OVERWORKING. Avoid over-vibrating or over-finishing pumice concrete. When using heavy concrete, segregation and over-finishing cause the paste to come to the top. With pumice concrete, it’s the coarse pumice particles that float to the top.

CURE. Pumice concrete is cured in the same method as is heavy concrete.

FORM REMOVAL. Form removal should be delayed for an additional 24 hours for pumice concrete. This applies especially if sharp corners are formed, as they will be softer for a few days.

Additional Resources

ABOUT PUMICE and HESS PUMICE

Brief information about the primordial origins of our pumice deposit and technical data on its properties and chemical makeup. Also an introduction to Hess Pumice Products Company and links to more.

SUPPORT DOCUMENTS

A downloads library of informational pumice concrete documents as well as declarations and certifications for various subjects and to satisfy various requirements:

OFFSITE LINKS

Links to other websites with content that may be useful:

Building (and Racing) Concrete Canoes

An opportunity for students to take engineering principles learned in the classroom and apply them in a challenging, curiously practical effort? Sweet! Stir in competitive components to add flavor? Even better. Heat the competition up with a prove-it race element? It’s on! Hundreds of engineering teams involving thousands of students jump into the months-long Concrete Canoe Competition every year.

A BRIEF HISTORY

Professor Clyde Kesler had an idea: class term projects involving high-strength concrete cylinders and reinforced beams lacked creative and collaborative depth...but a concrete canoe? Now that would stretch ’em out!

The first concrete canoe assignment was completed by Professor Kesler’s University of Illinois (Urbana-Champaign) concrete design class students in 1970. They named the 370-pound boat Mis-Led. Word was, the vessel resembled (vaguely) a canoe.

And word got around. The engineering students at nearby Purdue University determined to build their own concrete canoe and challenged Illinois to a race. That race splashed into history on May 16 of 1971: the first inter-collegiate concrete canoe race. Year after year, campus after campus, the itch to design, build, and race a concrete canoe spread.

The competitions were loose, localized, ad-hoc affairs until the ASCE stepped up in 1987, forming a committee to organize the competitions under a standard set of rules and feeder regions. The first National Concrete Canoe Competition was held in East Lansing, Michigan (Michigan State University) in 1988. The team from the University of California Berkley took top honors. The ASCE maintains a list of past winners.

The experience-rich, quirky challenge of engineering and crafting a concrete racing canoe spread internationally as well. The first international concrete canoe race was held in Stockholm, Sweden in 1981. International teams regularly come and compete in the American competition.

In another concrete canoe historical first, 25 high school engineering students competed as an exhibition team in a regional competition (the ASCE 2022 Virginias Symposium).

Led by Ryan Henry (one-time captain of the Clarkson University concrete canoe team), students from the Miller School of Albemarle worked the design, development¹, build, and documentation process requirements to compete in each category. On April 8, 2022, near the Lexington campus of the Virginia Military Institute, the WaveMaker slid into the quiet waters of Lake Robertson and the race was on!

1 | MSA students developed their concrete mix design using Hess Pumice aggregate and pozz.

GETTING IT DONE

Comprised of the winners of regional competitions held each spring, teams qualified to compete in the national competition finals gather in early June to a location hosted by one of the ASCE Student Organizations. Eligible teams must be members of a recognized ASCE Student Chapter or an ASCE International Student Group.

Teams compete both on the water and off, accruing points in various academic and race categories. The categories: presentation (oral and visual), technical paper, races (5 race categories), and overall canoe quality.

The Concrete Canoe Competition recently added a plus (+) to the scope of the national finals race event, welcoming the society-wide finals of the UESI Surveying Competition and the Sustainable Solutions Competition.