YouTube Transcript - make Lightweight Concrete Garden Boxes

Transcript


hi it's Kent from man about tools and
today I'm making garden box panels from
lightweight concrete
[Music]
this is part 3 of my series on casting
your own reinforced concrete garden box
panels these panels link together to
make long lasting rot proof garden boxes
in part one I made the forms from
plywood in part two I simplified the
design to make the forms easier to build
and for this video I'll cast the panels
with lightweight concrete
I've had many viewer requests to make
the panel's lighter so I did some
research into this it turns out there
are many ways to make lightweight
concrete so to simplify things I decided
to focus on just three formulations I
wanted to use readily available
materials that you could pick up at any
big box building or a garden supply
store or that you could easily order
online for the first mix I substituted
the gravel aggregate for lava rock in
the second mix I use to find vermiculite
and in the third I'll replace the sand
and gravel aggregate for foam and try an
air creat version of the garden panel
I'll show the mixing pouring and
unmolding and then look at the weight
and durability results if you haven't
watched part one in part two of this
series then you might get more from this
video if you watch them first there's a
link in the upper-right or in the
description below I'll be using the
forms I built in part one in part two I
have plans available on my website man
about tools.com
I also have a full blog post for this
video with all the formulations
ingredients and ratios for the concrete
mixes I let all the test panels fully
cure for a month keeping them damp and
covered then I let them dry for a week
or so before weighing okay so let's get
on with it here's the first formulation
so this will be my first attempt at
making some lightweight concrete this
blend uses Portland cement lava rock
sand and some glass fibre for
reinforcement you add about one pound of
this fiber per cubic yard of concrete so
when I calculated how much I needed per
batch it came down to a third of an
ounce per 48 inch panel so I just used a
pinch
so here's the proportions I used for the
first attempt at lava concrete one part
Portland cement three parts lava rock
two parts sand and just a pinch of glass
fiber these proportions are measured by
volume
I put the sand lava rock and fiber in
the wheel barrel first and blended that
before I added to Portland cement once
that was well mixed I slowly added water
I realized as I was doing this that it
wasn't looking as smooth as I had wanted
and it looked quite lumpy I thought well
I'll go ahead with it and put it in the
form I used a reciprocating saw without
the blade to vibrate the form and settle
the concrete mix then I laid in a piece
of reinforcing wire mesh this galvanized
wire mesh is cut from a large hog panel
fence I bought from my local farm supply
store then I topped up the rest of this
and vibrated it some more I tried to
smooth it out with a trowel and it
wasn't coming out very well but in the
bottom of the wheel barrel I had lots of
sand mixture leftover so I just did the
best I could with that for my second
attempt I changed the ratio of it I went
with one part Portland cement two parts
lava rock and three parts sand and again
a pinch of glass fiber I figured that I
needed to add more sand to get a
smoother mix so I started the same mixed
it all up in the wheelbarrow and it came
out a bit wetter than I liked so I added
a bit more sand to absorb some of that
water I could tell right away that this
consistency was closer to regular
concrete so same thing fill the mold
halfway lay in the reinforcing wire grid
and then vibrate and smooth it out I
used a little bit of the extra mortar
type mix in the bottom of the
wheelbarrow to improve this
surface finish on the first form and
this seemed to work pretty well I
covered the forms with plastic and left
them to set up the next day I removed
the formed sides and ends and these
castings came out fairly easily I was
pretty happy how the panel's looked but
it could tell right away that they were
a bit heavier than I expected
I went back to our landscape supplier
and got some lava rock that closely
approximated gravel this red lava rock
has a lot of smaller pieces instead of
the same 3/4 inch size I compared the
weight of gravel to lava rock for an
equal volume the lava rock weighed
approximately half that of the gravel
for my third attempt with this more
variable sized lava rock the mix I used
is one part Portland three parts lava
rock two parts sand and again a pinch of
glass fiber I measured all the
ingredients and mixed up a slightly
larger batch again starting with lava
rock the sand with fiber and then adding
the Portland cement and then the water
and into the forms as before it's
settled nicely with vibration and all
looked good
the next day I remove the plastic and
disassemble the forms these panels came
out of the forms quite nicely and this
was my final version of the lava rock
mixture so as you saw I substituted the
gravel for lava rock in this first
lightweight concrete attempt the lava
creat if you will worked very well once
I used a variety of rock sizes that
approximated gravel in my mix the finish
is very good and the panel feels solid
and durable this panel is approximately
10% lighter than regular concrete now
that's not a lot lighter but I'd say
it's almost equivalent in durability and
strength I had hoped that this panel
would be much lighter given that the
lava rock was about half of the weight
of the gravel I suspect that the voids
in the lava rock were filled with sand
cement and water during the mixing so I
lost most of those air spaces that would
have made it lighter okay so now let's
look at the vermiculite mix so for this
blend I picked up a bag of number three
vermiculite it's a mineral that's
expanded by heating in a furnace it
looks a bit like mica the ingredients
are Portland cement sand vermiculite
and glass fibre I wetted the vermiculite
slightly first before adding it to the
sand in the wheelbarrow
this makes it easier to blend for this
first test is one part Portland cement
two parts vermiculite and one part sand
and is always a pinch of glass fiber
this mixed easily in the wheelbarrow
once it's well blended I had to Portland
cement it felt quite dry and it took a
bit more water than I expected and like
before I fill the form halfway settle it
a bit with the reciprocating saw add the
mesh and then top it up and repeat on
the other form and smooth the bubbles
with a trowel and these are the
vermiculite 36 inch panels coming out of
the forms removing the sides and ends
and then just gently prying the panel
free with a paint scraper
now the vermiculite blend mixed very
well and felt much lighter even in the
wheelbarrow and this made it easy to
fill the forms it settled well with
vibration and had a nice texture while
troweling and edging it came out of the
forms easily and it has a nice smooth
finish it's noticeably lighter than
regular concrete and I think it would be
very durable as well it weighs on
average 38 percent lighter than regular
concrete now let's have a look at the
air Crete the air Crete uses fewer
ingredients Portland cement shampoo to
create a foam and some glass fiber for
extra strength
so I begin by diluting the shampoo and
water 15 fluid ounces of shampoo to two
and a half gallons of water and this
will be the dilution that I'll use to
create the foam I stir this with a paint
mixer attachment for my drill on a low
setting just to dissolve the shampoo in
the water I'll use suave daily
clarifying shampoo as my foaming agent
I'll use a digital scale to weigh my
ingredients I use nine point four pounds
of Portland cement five pounds of water
one point five pounds of the shampoo
dilution and a pinch of fiber I'm
weighing the cement and to that I'll add
a little handful of the fiber I then
weigh the water
and then I also weigh the shampoo
dilution and it's three pounds to make
my foam it's easier to make twice the
foam I need I find it just mixes better
I experimented with some different shape
mixers to make my foam with wire I sowed
some window screen onto this thin set or
grout mixer when I tried to make the
foam it's fun the entire mixture a bit
too much so this one was a little too
aggressive the next time I sewed the
screen to a smaller egg beater type
mixer I tried adding a little bit of
stainless steel scrubbing pad to the
center of it I don't think that really
made a difference either way so this one
worked better because it didn't spin the
entire mixture it didn't cause it to
overflow from the pail so I got a lot
better results this way I'm using a
five-gallon pail with three pounds of
shampoo dilution so when the pail is
full I get a foam density of 3 pounds
per five gallons all you
[Music]
now with a paint mixer I'll add my
Portland cement and fiber to the water a
bit at a time I want to create a smooth
Portland cement slurry so I add a bit
spin it
add a bit and spin it until it's smooth
I also stirred them mixed by hand to
make sure that there was no dried cement
stuck to the edge or clumps in the
bottom of the pail and this worked
pretty well now the slurry is ready for
the foam I add half the pail of foam to
the cement slurry I'll use my mixer to
blend it all evenly by hand stirred with
an improvised stir stick to make sure
that everything was blending right to
the bottom of the pail and I got a nice
even air creat mixture and this looked
really good then I added the air creat
to the form giving it a bit of a jiggle
to help settle it into the corners and
then I added a bit more to top it up I
tried to get as close as I could to
being full without over filling too much
a little bit over is okay because the
mix is going to settle and some of the
bubbles are going to collapse
then I can smooth it with a trowel and
then lay in the pipe wrap wires and once
it sets up a bit I gently lay in a
galvanized wire reinforcing grid so it
settles in right in the center and I
made a couple more batches and filled a
few more forms I was happy with how this
was blending and how the grid was
sitting in well I needed to push it into
place
so the air creat had enough density that
I felt comfortable that the wire mesh
was not going to sink all the way to the
bottom of the form it was a hot day so I
think that also helped the air creat to
set up faster and I think that's quite
desirable because then there's not as
much time for the foam bubbles to pop
when the air Crete was fully set up I
covered the forms with plastic and left
them for a couple of days I remove all
the screws from the form gently pry off
the sides remove it from the base and
then remove the ends and I was really
happy with how they looked they felt
quite solid
now this panel was the most fun to make
and certainly the most unique of the
options I tried I'd like to thank the
honeydew carpenter and Eric Reed Harry
for their many great videos on
everything to do with air Crete I'll put
a link to their channels in the
description as well I was able to get a
very dense foam without using a foam
generator for my testing this worked
well but if I was going to get into
making a lot of air Crete I'd build her
by a foam generator like the ones that
Harry or Darwin use I followed air Crete
Harry's formulation for what he referred
to as a standard mix my air Crete held
its shape and there was little if any
bubble collapse as it was setting up the
air crate panels came out of the forms
well the surface finish looks pretty
good and the bubbles looked uniform the
panels were very light on average eighty
percent lighter than regular concrete so
wow that's pretty impressive
but even after curing though I found the
panels were not very durable there's no
sand or gravel to add that impact or
abrasion resistance I did a little test
with all the panels by running a weed
eater or lying trimmer against them not
a scientific test by any means but
something the panels may have to endure
there was noticeable damage to the air
creep panels but the others fared ok
another bigger issue is what was
happening to the air creep panels as
they cured they were bending and
cracking I suspect that with a lower
strength in general the internal
stresses caused by shrinking and drawing
led to this bowling along its length and
then these cracks forming this is what I
think is happening anyways perhaps a mix
with a greater ratio of cement to foam
would prevent this it would bring the
weight up a bit and there's still the
durability issue if you've made these
panels with air Crete or you know how to
prevent this warping and cracking then
leave me a comment below and then maybe
I can get a chance to do a few more
tests
so I think for me of these three the
best formulation for ease of mixing
weight reduction and durability is that
vermiculite blend if weight was an issue
for my concrete panels I doubt for the
vermiculite mix I'm not saying that the
lava-rock mix are air creat are not
worth trying because you might get
better results than I did
there's also lightweight concrete Ready
Mix bags made by sac Reid but they're
not available in my area so I was unable
to test that so that might be a good
option for you as well one last thing as
I was doing these tests that came up
with another way of making the panel's
that's faster and lighter without
sacrificing any strength or durability
and that's coming right up in part four
thank you so much for watching we'll see
you next time I thanks for not falling
asleep it's like watching paint dry
sometimes I'm sure mixing concrete
mixing concrete pour it in the forms let
it set up and repeat okay see ya