NORTHERN ARIZONA UNIVERSITY CONCRETE CANOE

2020-2021

SUMMARY OF

CONSTRUCTION METHODS TESTING

Russell Collins

Marie Cook

Kyle Julle

Scott Murphy

Ryan Wassenberg

April 27, 2021

To Whom It May Concern:

This year was all but normal when it comes to concrete canoe and the 2021 team did not actually

construct a full-scale canoe because there was no in-person competition. PSWC was held virtually

this year and the team decided that it would not be in our best interest to use the materials to build

a full canoe and then not use the final product for anything. Because we did not have to spend the

time constructing a canoe, we decided to focus our attention on construction methods testing. The

document is an overall summary of our findings during our testing. This includes our

recommendations based on our experiences. This way, all of the time we put into these tests will

not go to waste. This report includes a one-page summary table for quick reference as well as in-

depth explanations and analyses of the results we obtained.

Thank you for taking the time to read through our summary,

NAU 2020-2021 Concrete Canoe Team Ponderosa

Marie Cook

Project Manager

Russell Collins

Mix Design Captain

Kyle Julle

Hull Design Captain

Scott Murphy

Structural Design Captain

Ryan Wassenberg

Quality Assurance/Quality Control

Table of Contents

1.0 MINI BEAMS ...................................................................................................................... 2

1.1 Mini Beams Set One ............................................................................................................. 2

1.2 Mini Beams Set Two ............................................................................................................ 5

1.3 Mini Beams Set Three .......................................................................................................... 8

2.0 COLOR TESTING .............................................................................................................. 9

3.0 SCALED 3 FT CANOE..................................................................................................... 10

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Construction Method Result

Release Agent On top of flex seal, Vaseline or a commercial agent is best.

On top of wood, mineral oil works best.

Reinforcement Splicing

(overlapping)

For stiffer mesh materials (like basalt), splice needs to be at least 1

in.

For more flexible mesh materials (like fiberglass), splice needs to

be at least 2 in.

Color Dyeing your concrete can be used with three different products:

1. Typical concrete dye for brown, black, terracotta, clay, other

rocky dull colors. You can find these from a supplier or from Home

Depot.

2. Latex paint (you can get made in any color at Home Depot.

NOTE: latex may or may not be banned your year! Adding latex

paint is equivalent to adding latex to your mix! Also, your paint

must be water-based! If you use oil-based paint it will not work.

3. If latex is banned, try to get your hands on BASF PureOptions®

Colorant. It’s the colorant/dye they use in paint. Make sure to test

this before you pour your final canoe and get an FRI on it to make

sure it’s allowed your year.

Shotcrete Using shotcrete requires a special mix. The only way to get a

working shotcrete mix is to do it by testing. Although, here are

some pointers that may help:

1. Use more cement or cementitious materials than you normally

would (700 to 800 lbs total of cement & cementitious material).

2. Try to use as many spherical particles as possible for your

aggregate. If microspheres are allowed, these are probably the best.

3. Use aggregates graded to a fine sand at the highest possible

content. Actual sand is best, but it is also very heavy and not

practical to use for floating concrete.

4. Use admixtures to your advantage. If you need to add a lot of

water reducer to your mix, also use a viscosity modifier so that the

concrete does not start segregating.

Three Point Loading Test for

Flexural Strength

Since NAU does not have equipment that can do small beams, you

need to adapt ASTM C78 as accurately as you can. See pictures

below for the ways we adapted ASTM C78.

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1.0 MINI BEAMS

To kick off our construction methods testing, we constructed mini concrete beams so that we could

perform testing on these. Not only did these help us with releasing agents, reinforcement decisions,

and practice with the shotcrete application method but we were also able to obtain our modulus of

rupture using the beams. See the following subsections for the results from each set.

1.1 Mini Beams Set One

We started with just making one set of 6 mini beams by constructing wood molds for them. These

wood molds made beams that were approximately 6” by 16” by approximately 5/8” thick. Ideally,

the beams would have been 0.5” thick because this was our design thickness for our actual canoe,

but we were restricted to the thickness of the wood used to create the molds. For the releasing

agent for these molds, we used mineral oil because they are wood. Mineral oil worked great; the

beams basically fell out of the canoe once we were ready to remove them. To apply the mineral

oil, we made sure to soak the wood with mineral oil multiple times prior to pour day. We created

these molds on a Wednesday and saturated them with mineral oil that day, then we saturated them

again on Thursday, and then we also applied more mineral oil right before pouring the concrete on

Friday. We are not sure if this much mineral oil application is absolutely necessary, but we do

know that it was extremely effective for us. Photo 1 below shows the molds created for these

beams.

Figure 1: Wood Molds for Mini Beams

Once the molds were all prepped with the mineral oil, the team decided to pour the concrete in a

similar layering scheme as we would for the canoe. So, this means we did 1 layer of concrete,

applied the mesh reinforcement, then applied two more layers of concrete. We did apply the

concrete through a shotcrete application method. We wanted to test two different mesh

reinforcement materials, so we did 3 of the beams with the basalt mesh that has been used in a

recent years and 3 of the beams with a fiberglass mesh that the team purchased this year for testing.

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See the photos below to see how the shotcrete was applied as well as the curing chamber the molds

were placed in after they were completely poured.

Figure 2: Applying Shotcrete

Figure 3: Mini Beams in Curing Chamber

Since we wanted to do a 7-day test of our beams, we put the beams in our curing chamber for 7

days while keeping the humidity above 95%. Be careful of pooling water on top of the concrete in

the curing chamber as water drips from the top of the chamber. To prevent this we took extra

pieces of plastic and covered the beams. Once the beams cured for 7 days, the team removed them

and by looking at the figure below, you can see that they were easily removed from the mold

thanks to the mineral oil.

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Figure 4: Removal of Beam from Wood Mold

The same day the beams were removed from the mold, the team performed three-point loading

tests following a slightly modified version of ASTM C78. This testing provided us with our

modulus of rupture – which can also be calculated without completing this test. We also calculated

the modulus of rupture separately and compared the value and they were extremely close which

was satisfying to see. The three-point loading test also helped us decide which mesh reinforcement

we wanted to use. The reason we wanted to try something other than the basalt mesh is because it

is extremely difficult work with from a constructability aspect – it is extremely rigid and does not

shape well to the hull of the canoe. On the other hand, the fiberglass mesh was almost like a blanket

and not rigid at all. This made it way better from a constructability aspect than the basalt mesh.

What we learned fairly quickly from the three-point loading tests is that although the fiberglass

mesh is better to work with, it does not provide the same high strength that the basalt mesh does.

See the photo below for the setup we used to perform the three-point loading tests.

Figure 5: Three Point Loading Test

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The table below shows the results obtained from the three-point loading tests. The data that is in

grey text is data that was not used toward our final modulus of rupture calculation because the test

was inconclusive. We determined that a test was inconclusive if the last weight added onto the

beam before it broke was too large for what should have been placed. For example, if a 10 lb

weight was placed on the beam and it immediately broke, we recognized that we probably should

have placed multiple 2 lb weights to get the most accurate breaking point. Though it may take

more time, smaller increments of weight will provide you with the most accurate data.

Table 1: Three-Point Loading Test Results (Mini Beam Set 1)

ASTM C78 Flexural Strength of Concrete (third point loading)

Mesh Type

Specimen # lbs span length

avg width avg depth bd2 Modulus of Rupture

fiberglass

60.36

0.625

2.34375

309.0432

psi

fiberglass

56.042

0.625

2.34375

286.93504

psi

fiberglass

53.562

0.625

2.34375

274.23744

psi

basalt

70.488

0.625

2.34375

360.89856

psi

basalt

52.934

0.625

2.34375

271.02208

psi

basalt

46.042

0.625

2.34375

235.73504

psi

Overall, the construction and testing of this first set of mini beams was educational for the entire

team but the team did not want to simply stop there. See the next section regarding the second set

of mini beams.

1.2 Mini Beams Set Two

The goal of the first set of mini beams was to obtain our modulus of rupture and test our mesh

reinforcement options. The goal of the second set of mini beams was to decide what the best

releasing agent is using the same material as our proposed mold: foam. Instead of constructing

wood molds for this set, the team used leftover foam from last year’s canoe mold to construct new

mini beam molds. A total of four molds were created and each of them had a different releasing

agent on them. Prior to applying the releasing agents, we applied flex seal to the foam. We quickly

learned that we should NOT USE SPRAY ON FLEX SEAL WITH FOAM MOLDS. The

chemicals in the spray can that allow the flex seal to spray actually eat away at the foam mold and

may completely destroy the mold. Luckily, we realized this on mini beam tests instead of on an

extremely expensive full scale canoe mold. See the picture below to see each of the foam molds

with the flex seal and releasing agents on them. From left to right, the releasing agents are Vaseline,

½ mineral oil/ ½ vegetable oil, 10 parts dish soap:1 part water, and Liquid Release (commercial).

These molds were cured in the same curing chamber as the first set of mini beams.

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Figure 6: Mini Beam Set 2 Molds Before Pour

Overall, the removal of the beams from these foam molds was much more difficult than the wood

molds. From the best to worst releasing experience, the releasing agents are: Liquid Release,

Vaseline, dish soap, mineral oil/vegetable oil. The beam that had Liquid Release came out overall

very easily. The Vaseline one released with just a bit more work than that of the Liquid Release.

Both the dish soap and the mineral oil / vegetable oil combination worked horribly. They basically

didn’t release and bonded with the Flex Seal. The dish soap beam actually had to be sawed off of

the mold. See the photos below.

Figure 7: Liquid Release Beam

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Figure 8: Vaseline Beam

Figure 9: Dish Soap/Water Beam

Figure 10: Mineral Oil / Vegetable Oil Beam

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Besides varying the releasing agents for these beams, we also implemented different layering

schemes for the reinforcement. Instead of one solid sheet of mesh for each beam like we did in the

first set of beams, we put cut the sheet in half and did two splice orientations. Two of the beams

had a 1” splice length and 2 of the beams had a 2” splice length. As you can see in the table shown

below, only three of the beams could be tested for the three-point loading. This is because the

beam that had the oil combination as a releasing agent was unusable.

Table 2: Three-Point Loading Results (Beam Set 2)

ASTM C78 Flexural Strength of Concrete (third point loading)

Mesh Type

Specimen

# lbs

span

length

avg

width

avg

depth bd2

Modulus of

Rupture

1" overlap

elease

125.972

0.5

755.832

psi

1" overlap soap

108.782

8.25

0.5

2.0625

632.9134545

psi

2" overlap

Vaseline

93.1

8.25

0.5

2.0625

541.6727273

psi

When comparing the one good test for the 1” and the one good test for the 2”, the difference in

splice length did not seem to have an effect on its strength. This could mean that the splice length

for the basalt mesh doesn’t need to be any more than 1” but because of the lack of repetitive test

results, more testing would be necessary to understand the full effect.

1.3 Mini Beams Set Three

We were not satisfied with our results from the second set of beams, so we went ahead and created

4 more foam molds. In these molds, 2 of them had the commercial releasing agent and 2 of them

had Vaseline. We wanted to continue our tests for the Liquid Release and the Vaseline because

although the Liquid Release did work a bit better than the Vaseline, the Vaseline is more readily

available and would contribute to a sustainable canoe in terms of simplicity. So, we wanted to see

if that may have been a fluke that the Liquid Release worked better. Overall, we thought that the

Liquid Release and Vaseline had similar affects as a releasing agent but because of the material

availability of the Vaseline, we would recommend continuing to use it rather than switching to the

Liquid Release. One thing to keep in mind is that after taking the concrete out, there will be some

Vaseline still on it and that will need to be cleaned prior to sanding.

As you can see below, the values obtained for Modulus of Rupture for these beams varies quite a

bit. This is for a couple of reasons: (1) there are two different mesh layering schemes within these

beams (one of the beams has a double layer of fiberglass mesh to see if that would provide more

support, one of the beams has a basalt 1” overlap, and the other two beams have a 1” fiberglass

overlap), (2) the modified ASTM C78 testing can be finnicky to work with and often takes a test

or two for the operator to adjust, and (3) the basalt mesh data is skewed as you can see and this is

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because the mesh actually popped up to the surface as it was curing and was no longer centered in

the concrete. The reason this skewed the results is because the side with the mesh reinforcement

was placed down during testing so the value shown in the table listed below is not the modulus of

rupture for the concrete, but it would really be the breaking point of the mesh.

Table 3: Three-Point Loading Results (Beam Set 3)

ASTM C78 Flexural Strength of Concrete (third point loading) MARCH 14

Releasing

Agent Mesh Type

Specimen

# lbs

span

length

avg

width

avg

depth bd2 Modulus of Rupture

Liquid

Release

fiberglass (double)

54.522

0.625

2.34375

279.15264

psi

Liquid

Release

basalt (1" overlap)

166.14

0.5

1.5

1329.12

psi

Vaseline

fiberglass (1" overlap)

58.282

0.5

1.5

466.256

psi

Vaseline

fiberglass (1" overlap)

77.17

0.5

1.5

617.36

psi

2.0 COLOR TESTING

Beyond creating and testing the mini beams, we decided to test out some coloring methods.

Concrete dye is often very expensive and NAU teams usually aren’t rolling in the dough, so we

tried to find a cheaper option to make colored concrete. To do this, we started with latex paint. We

started here because it was the cheapest option for us to just get samples of paint from Home Depot

to color our concrete. The point of using paint was to see if the same pigments they use to dye

paint can be used to dye concrete. The dyes they use for paint are not sold in retail, but BASF

actually makes them, so get into contact with a representative from their pigment department. The

product you are looking for is BASF PureOptions® Colorant. A couple of things to note about

this:

(1) If you want a vibrantly colored concrete, be sure to make a light-colored mix that is tailored

for this. If you want a more muted tone, make a whiter mix (see Figure 11), if you want a

darker tone, use a darker mix. A good medium between these two would be to use white

cement with fly ash. Aggregates don’t affect the color once everything is dry.

(2) The rules change every year, but the use of latex paint is not usually permitted for the

competition (make sure you follow the rules!!)

Russell’s thought process when starting with the latex paint was that if we could successfully

“steal” the pigmentation from the paint, then we could source the dye they use and try to purchase

just that. The results from the latex paint dye are shown below and the concrete did turn out to be

very vibrant. All of the cylinders in the photo were made using a very white mix except the darker

green on the far left was made using our final mix design for this year.

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Figure 11: Colored Cylinders Using Latex Paint

3.0 SCALED 3 FT CANOE

The scaled 3-foot canoe was a huge learning experience for us, and we highly suggest that you

construct a scaled canoe to understand the process of creating a concrete canoe. In this process we

learned what to do and what not to do when constructing a concrete canoe. Ultimately, the 3’ canoe

pour we did was to test certain construction methods and products. We used a female mold and

cut out foam cross sections for it. We used a combination of saws and knifes to cut out these

sections, but some sort of hot wire would be best.

To create the cross sections of the canoe we used the construction drawings and scaled up or down

the largest cross section to create the templates of each cross section at different distances from

the largest cross section. Marie was able to scale each cross section in Bluebeam. If we were to do

this step again it would be better to get the actual cross section from either SolidWorks or

MAXSurf. Figure 12: Cross Section shows the cross section used for scaling up or down.

Figure 12: Cross Section

The way we marked the cuts for our cross section involved printing out various scaled cross

sections of our canoe on pieces of paper and then taping those cross sections each panel of our

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mold. For our mold we used Styrofoam for housing insulation. There are some extra sheets in the

back room of the farm. Then we cut away the paper and the mold to the desired shape. This is what

tattoo artists do when they sketch a design on your skin—print out the design, place it on the skin,

trace the lines on the paper, remove the paper and then start inking on the traced lines. Maybe they

have more modern methods to do this, and I can be totally wrong, but you get the idea.

Once our cross sections were cut out, we applied flex seal via a spray can. This is the first Lesson

Learned of this test, as it was a total failure. Whatever chemicals they use in the spray can and not

in the paint pale seems to dissolve foam. In the future, make sure to paint your flex seal on, DO

NOT spray it on. Otherwise, flex seal is a very effective and an easy barrier to apply to your foam

mold (to keep the concrete and the mold separate), and as a team we highly recommend using it.

Another method that may work is to shrink wrap your mold completely and use that as the

barrier—however, this is only effective with a male mold and not a female one.

When applying your concrete make sure to use tools. Never use your hands. Find people who are

familiar with a trowel as it is the best tool for finishing concrete. Pin rollers (like the ones they use

for making dough), are also a good tool for those not experienced enough to be comfortable with

trowels. Also make sure before placing your concrete you add your releasing agent. For our mini

canoe we used a LOT of Vaseline.

If using a female mold, you need to work your edges while the concrete is still wet. To do this, use

two trowels, one in each hand, and press a trowel vertically up against the edge and tilt it until you

get a gap that is the desired width of your canoe. Then, fill that gap with concrete and work it with

the trowel in your other hand. Go along the length of the canoe until all edges are properly finished.

Keep a spray bottle with you full of water and keep adding water to the edges so the concrete does

not dry too quickly. Be sure not to add too much water, just enough so that the surface is moist,

and you don’t have water evaporating out of the concrete.

When we removed the mini canoe, it was easily removed from the mold. However, the canoe was

covered in Vaseline. To remove the Vaseline, we rubbed dish soap on the canoe and washed it like

a car. This had to be done multiple times to get all the Vaseline off. Then we let the canoe dry for

multiple days. After the drying process, the canoe can be sanded and finished.

This was the final test that we conducted for our year and we hope that this document helps out

any team that reads it! As always feel free to contact anyone of us if your team has any questions.

Best of luck designing and building your concrete canoe and GO NAU!