NORTHERN ARIZONA UNIVERSITY CONCRETE CANOE
2020-2021
SUMMARY OF
CONSTRUCTION METHODS TESTING
Russell Collins
Marie Cook
Kyle Julle
Scott Murphy
Ryan Wassenberg
i
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
ii
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
1
60.36
12
6
0.625
2.34375
309.0432
psi
fiberglass
2
56.042
12
6
0.625
2.34375
286.93504
psi
fiberglass
3
53.562
12
6
0.625
2.34375
274.23744
psi
basalt
4
70.488
12
6
0.625
2.34375
360.89856
psi
basalt
5
52.934
12
6
0.625
2.34375
271.02208
psi
basalt
6
46.042
12
6
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
L
-
R
elease
1
125.972
12
8
0.5
2
755.832
psi
1" overlap soap
2
108.782
12
8.25
0.5
2.0625
632.9134545
psi
2" overlap
Vaseline
3
93.1
12
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)
1
54.522
12
6
0.625
2.34375
279.15264
psi
Liquid
Release
basalt (1" overlap)
2
166.14
12
6
0.5
1.5
1329.12
psi
Vaseline
fiberglass (1" overlap)
3
58.282
12
6
0.5
1.5
466.256
psi
Vaseline
fiberglass (1" overlap)
4
77.17
12
6
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!