How Strong is Lightweight Concrete? - Deflection Test Perlite, Vermiculite, Lava Rock, CSA Panels

I test the deflection under point load of several lightweight concrete garden box panels. These panels link together to make long lasting rot-proof garden boxes. I test 4 lightweight panels made from Perlite, Vermiculite, Lava Rock with portland and CSA cement. Some broke and some didn't.
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#lightweightconcrete #concretetesting #concrete

[@MANaboutTOOLS]

I now have molds ready-to-go here: manabouttools.com/store-plastic-concrete-molds/

[@unclefester6501]

As a mechanical engineer I have some suggestions for your testing. You are not doing tensile testing. You are doing beam loading with a point load in the middle. With a 500 lb point load the center of the beam sees the full 500 lbs and each end sees 250 lbs (so the pins only see 1/2 the load). This is not a good simulation of the dirt or ice load in your garden bed. Try a distributed load by putting at least three layers of bricks across the full face of the the panel, offsetting the seams, and then add more load (bricks or bags or whatever) evenly across the top of that. You should get a failure at the pins and you may be able to reach the theoretical weight of your truck wheel. (If you do another truck test build two ramps so you actually get even loading, you had more than 1/2 the rear truck weight on that one elevated tire.) This will also eliminate the chance that tall pile of bricks might fall on your head when you bend down to look for cracks. Had me worried a couple of times. Thumbs up for an excellent and thorough series, who knew it would be this fascinating?

[@AZ-NY]

You're absolutely right, I was going to suggest the same. But since you took the liberty of writing it all out. I just up voted your comment. Thanks.

[@russellborrego1689]

There's a handful of KZbinrs who's videos I enjoy watching because they are so well presented. You are definitely in that group. Great work! 👍👍

[@MANaboutTOOLS]

Thanks you very much! I so appreciate the support!

[@CitizenAyellowblue]

I agree. Cheers from Australia.

[@SquirpCo]

I can't tell you how much I appreciate the time and effort you've put into this series. You've saved hundreds or thousands of us from making inferior mixes, jumping to faulty conclusions, or spending hours re-creating your experiments when... now we can just appreciate your transparency and due diligence and learn with you. Frickin' liked and subbed. Thank you.

[@MANaboutTOOLS]

I incorrectly referred to this as a tensile test when it is actually a deflection test. Thanks to the engineers out there that caught my error.

[@austinharding9734]

i thought something was off about that isnt tensile force pulling it apart? aand an i thought what u did was considered a shear test?

[@strenghkey8]

Give you considered adding decorations? Colored glass or stone could be put into the mold before adding concrete Awesome series!! These are good enough to sell vacuum formed molds in mass production at be carried by a big box store

[@seandevine9846]

The biggest problem with this kind of test is the metal that you put inside of that is what gives the concrete it's strength in that dimension. The metal you used in some of them was very thin. I believe the one that has the Hague wire will perform the best. If you noticed in your concrete test where the truck broke it The edges of the concrete did not flake off under pressure of the truck tire. If you recast that same one with the same mixture but instead were to add 2 or 3 pieces of hogwire offset for each other so that the pieces coming out to the top and bottom were not on top of each other but spread out you would be able to support a truck.

[@ForensicCats]

Actually all your test failured under tension and you never measured deflection... point of fact, the expansive loads you theorize is from water retention in the soil that would expand and that small dimensional box would not create enough pressure...

[@unionse7en]

it's still highly related to the tensile stress because the bottom of the beam is in tension and that is the critical failure. Deflection is just how much it deflects per load, not necessarily to failure. UTS Ultimate Tensile Strength IS what you tested, albeit in a bending mode, rather than an axial test. The maths to calculate this bending failure would still use the UTS as a primary input to the equation. Stiffness, "Modulus of Elasticity" would be used to calculate deflection not UTS.

[@J-RallySite]

First and foremost - I love this series. It's going to be the basis for a big experimental project I'm starting. One point you might consider - you are deflecting with the steel on the inward side / radius where compression occurs. It would be stronger if the steel was place on the outward side where tension occurs. It might be interesting to take too similar panels and flip test them. I'd bet having the steel on the outward side will near double performance.

[@methere27]

although you said its not scientific it still holds a lot of value to see the breaking points of each type of mixture. thanks for the hard work, I think you can skip the gym this week

[@Carknocker001]

We recently bought a house in an area with expansive soils and temperatures that drop below 0 (F). Your testing is very relevant to our situation and I am very grateful for the effort you are expending on this project. Thank you!

[@rickrossi7471]

I am impressed with your creativity and dedication to this topic. You address a lot of the issues discussed in engineering literature regarding concrete mix design, placing, curing and testing. One thing in particular I would like to note is for your beam (simple point load) test the tension exists in the lower portion (exterior side) of the panel so the reinforcing would be more effective the if it was placed as close as possible to the exterior face. Additionally your pin locations didn't fail because there is very little tension there, mainly shear force.

[@cyotedude]

A great test of the blocks, thanks for doing this. A lot of labor you endured doing this. It is appreciated, I was curious after reviewing your recipes and your process.

[@MANaboutTOOLS]

Thanks!!

[@regulovanduck4696]

I am fascinated with this series, so well presented, so fine and i love the fact that a how to video on concrete planters turn into a civil engineering class. super fan of all your work. thank you very much.

[@IAMSatisfied]

I appreciate how your mind works, Kent. I also appreciate you sharing your testing with us! I look forward to the aircrete panel tests.

[@MarkLawsonY3K]

Keep experimenting. We got massive cylinder crush pressure by adding perlite to our portland sand cement. Our goal was less is more as we didn't want any of the perlite touching other perlite granules (very subjective). Lawson Texas

[@Zekespeaks]

Kent, I've watched from part one through this one and you have given me many ideas on how to address a problem I have on my property. I'm pretty sure I will use a version of your design with a vermiculite mixture to rebuild a planter berm that I made years ago to minimize the occasional flooding from our creek. Thank you for sharing this.

[@myperspective5091]

I liked all of your videos so far. Your narrations flow smoothly.

[@MANaboutTOOLS]

Why thank you very much!

[@victorabadia9700]

My back hurts after watching! I live In Puerto Rico and these panels would be a hit for fencing.

[@MANaboutTOOLS]

I got a good workout for sure. Cheers, Kent

[@austinharding9734]

hell yea from SoCal but part Puerto Rican from San Herman!

[@doubledarefan]

I have thought, reinforce it with post-tensioning, but thinking about that now, that would be overkill. They are garden box panels, not bridge decks.

[@robertcullity1695]

I don't know if you have an engineering background but your approach is right up there. I've made forms from your videos and I love them. I use the perlite mix and heavy gauge 4 in x 6 inch heavy gauge hog panel . I'm a retired general contractor and have poured in many different forms more than 7 million square feet of concrete in 20 yrs of work. Based on a 4 inch thickness. Love your videos and keep them coming. I have added tile mosaics and face brick for custom pieces to the face inserts. Well done! Rob

[@Ilamarea]

The crack on the first test with bricks was caused by the uneven support of the wood at the bottom. The right one was shorter, which caused pressure to accumulate on its far edge where the crack formed.

[@mikesgarage394]

Found thie just in time, wood is crumbling on my raised beds and will be doing your forms, just deciding on the mix.

[@mori8424]

An ounce of prevention is worth a pound of cure. To minimize the effect of frost pressure, line the inside of the planter to the top of the dirt level with a material that will compress when pushed against. This will act as an expansion joint to absorb the dirt’s expansion. Good drainage under the planter will cause less water and then less expansion.

[@richardhutchinson4406]

Very well presented... The truck right in the beginning was definitely being optimistic, 🤪 but I love that you showed your whole process, including the parts that failed. I personally would've thought the shop press would be the best idea, but it turned out to be a complete bust. Keep up the great work, you saved me a ton of time not having to test these myself!

[@thantsintun100]

Thank you for your hard working to get those results.

[@MANaboutTOOLS]

My pleasure!

[@michaelhaidee]

Cool video.👍 When you load the panels your greatest force, or moment, is at the middle of the beam, not at the pins (hence why they don't break there, as each pin is a split or ratio of the load). Also, your wire mesh is negligible or zero in contributing any kind of reinforcement bcuz of the tiny size AND placing it in the center of the panel, or the neutral axis. Reinforcement need to be placed in the bottom portion of the cross section for the steel to be in tension. So really you're just testing the concrete itself, and you're loading the panel sideways. 🙂 Yeah I am one of those engineers. But not the kind that drives trains. Lol.

[@MANaboutTOOLS]

Yes, I agree with your points. I went through a few loading scenarios and also thought about a uniform pressure on the panel instead of the center. And that would have put more pressure on the pins. I might still do that yet and see what happens. All and all, I was happy with results. It was interesting to see how much concrete can flex. Thanks for the comments!

[@shauntoochaos235]

The concrete above the pins is also in compression, just compression upward. The center will always have the most tension because it will always have the easiest time deflecting. While the metal wont help like rebar since it isnt pretensioned, it will help in keeping the concrete as one unit for looks and hold the small amount of pressure a planter box holds.

[@1982MCI]

Michael & Haidee I was gonna say almost the exact same thought but you beat me by one day but well said Brother!

[@ewetoobz3840]

@@MANaboutTOOLS Great effort, I bet that was exhausting!! I wondered about the changing moment between tests myself , the press was dead center, the others varied the distribution over the panel by varying lengths and the truck test would have been like the press test if you had used a hydraulic jack to lower it in the center. If you haven't seen the Mathias Wandel testing on wood joints, it might be helpful for using a bathroom scale and a cantilever for mechanical advantage? "Dovetail joint vs box joint strength test" is the video title about 1 minute in is what I was thinking about when I saw your testing. Still good information, thanks!

[@joshl90]

If the concrete at the pins was going to fail, it would have been a shear failure since it is a pin/roller connection and takes no moment

[@evandavis8425]

I plan on trying this for my garden, tired of wood rotting out. May try it for flower borders but may try half rounded molding for a fluted look. May try making curves by using shorter sections, 2 feet or less using understatement plywood fastened to a curved form. Would start filling in middle then covering with curved plywood to hold in place. Good presentation.

[@mattevans-koch9353]

Your method of testing reminded me of my first physics class at college nearly 50 years ago. The professor used real world examples of the various principles-wedges, pendulums, etc. and was mesmerizing in his presentation. Thank you for showing these tests. While not "scientific" in the current modern sense they are practical and show the durability of these panels. And you saved yourself a gym membership! Two observations: 1. The size of the reinforcing and the density of the grid will affect the tensile stress the panel will handle. If there were for example 4 longitudinal rods versus 2 you will see higher loads. 2. The distance of the reinforcing from the neutral axis towards the tension surface will also increase the tensile loading possible. If the inset were half as deep and the reinforcing were closer to the inset you would see an increase in loading before failure, but the panel would not look as good. Ultimately I believe the failure of the panels will be from the freeze/thaw cycles and absorbed moisture and that will take years. Thank you for your videos. Take care, stay well and keep having a good time.

[@MANaboutTOOLS]

Excellent notes here! Thanks very much!

[@tealkerberus748]

What would happen with rebar in the thicker part of the panel above and below the inset? it would have to be just bars, not mesh, but we're not really worried about them breaking the other way.

[@adamliske]

So... they are plenty strong for most applications. Now you should do a beam strength test. That one you should be able to use your press for. I copied and modified your design and I have my first batch done and getting ready to cast second round today. They are a nice panel design!

[@georgemaze7926]

Thanks for making this video again, I'm going to use your formula of concrete because I know it works ( TEST ) .please keep up the good work.

[@MANaboutTOOLS]

Thank you! Cheers!

[@BenMitro]

You may find that dual reinforcing mesh separated as much as possible within the structure will give you the greatest strength. You might be able to use lighter gauge reinforcing mesh too.

[@MANaboutTOOLS]

I agree! I used that in two of the aircrete panels from Part 3.6. I'll be testing those next. Will be interesting to see what the difference is.

[@jmortonsalt]

First off - once again, GREAT information Kent! Love your passion about these panels and the amount of information you share about them. I would have loved to see you test one of the thin panels you made with the CSA Rapid Set Mortar Mix.

[@MANaboutTOOLS]

Thank you very much!! I really appreciate the support my channel has received. If you notice I have an extra smaller diameter hole in the blocks that hold the steel bars. Thinking ahead to testing the CSA panels in the future.

[@sdushdiu]

It would be useful to know if fence posts made in a similar manner would be sufficiently resilient

[@3Sphere]

Yes, fence posts of concrete with perlite. Would be very strong and cheap if you mixed the concrete yourself and the archaeologists would find them in 1000 years and wonder what kind of religious ritual they were for or if they told the time........ LoL....

[@Sylvan_dB]

I've been considering the same thing. :)

[@1982MCI]

sdushdiu very interesting!!!! I have a new section of pasture I need to fence and would love to try this idea. I wonder what would be the best way of attaching the fence to the post? Would you inset something into the post when pouring to attach fencing or is there a wrap around wire fastener and just pour a square post? I need to research this tho and find a solution so I can start making posts. If you have any other great ideas for them let me know and I’ll try them and see if it would work. Thanks for the idea, I greatly appreciate it!!

[@2003netguy]

Don Pfeiffer I’m looking at the same with the Thin CSA panels. I didn’t see him test those panels though.

[@sdushdiu]

Don Pfeiffer I guess it might partially depend on what you intend to attach to the posts for fencing. Insulators on stand offs could easily be embedded in the posts for electrified fencing (or simply the possibility of adding such capability, or simple a floating heavy duty chain link attached to resilient leads that will not rot or corrode over time embedded in the mix ( even tied to the post's rebar reinforcement). I tend to think in terms of traditional open wire mesh fencing (primarily gor livestock), newer high deer 'nylon' mesh fencing. As well as potential combination of the two, and even for the possibility of a rail style fence, although I suspect that material fatigue over time might result in rather significant warpage of such rails . Notre that is based on worst case assumptions and not on empirical fact! If you can suggest the type of fencing material to be attached I think we could come up with a few economical resilient long term suggestions....

[@Mr.GucciClass1A]

Hi there. Okay, so first and foremost thank you for your service. You are not just a good person but a Healthcare worker during these trying times, and whilst dealing with all that you are still responsible and Diligent about not letting your YT peeps down. Thank You! Ok. So... I of course decided to use your form plans and use the CSA!! FML, of all the choices I chose the dumbest! 😂 Funny thing was I knew this was the lightest the other day when i finished my first batch and as I was showing my brother via FAceTime (keeping healthy social distancing) one is the 24 inch panels fell back and well... Cracked right in the center! 😂 It’s just me. Nothing I try from YT works out. 😉 Anyway. Thanks for the info and god bless man. Btw: you’re very handsome. Wifey is lucky!

[@aomanchutube]

Very cool. I thought for sure the light concrete would be weaker, but now I see that the fibers and steel add much needed toughness to the material. Jumping over to aircrete... surely that stuff will crumble!

[@jmickart]

Thank you for your videos! The testing is great and way over the top! Any of these planter box panels seem to be far superior to any commercial version. Even at a tenth of the demonstrated strength, they should last a millennium, unless you intend to make bridges with them in the future.

[@MANaboutTOOLS]

Thanks! I agree that they are all strong enough for their intended purpose. But, I think it's still interesting to see HOW strong. Cheers, Kent

[@tealkerberus748]

I think the line-trimmer test was pretty critical to their intended service, though. The rest of it was just for the fascination of watching practical engineering in action.

[@tempeleng]

Thanks man. I learned a lot about lightweight concrete from your videos. The animations are really helpful.

[@MANaboutTOOLS]

Glad to hear it!

[@joshuamerriott9008]

Saw your recent video with the new molds. Very impressive. I would be interested to see you try modifying the placement of the reinforcement inside the mold. Positioning the reinforcement closer to the outside edge would increase the strength since that is the point of greatest tensile stress. Maybe two sticks of rebar on on opposite sides of your decorative inlay?

[@SCComega]

So, a couple things I'd be curious about, would be a variety of tests using fiberglass. Perhaps a test with continuous fiberglass rebar of various sizes, as well as a test using fiberglass insulation as a filler material, if such might be possible? Also, perhaps tests between aerocrete and standard concrete, also maybe using traditional methods vs using an ultrasonic vibration cleaner to try to even out the mold. Performance with a variety of aggregate grain sizes might also be an interesting test.

[@TungNguyen_lxag]

Horizontal concrete slabs will be subjected to pull from 2 ends, not pressure. So it needs a steel core for bearing. You put a lot of steel at the ends of concrete slabs, so the two ends have very good bearing while the middle is less steel and disjointed with the two ends, so the middle will be weak. But I think they can withstand nearly 200 kilograms of pressure, which is good enough for making pots. Thanks for sharing your good ideas. :)

[@geheirnwaeshen]

Weight of the truck tire was on the wood block as it passed over the pin, and as it rolled off the wood block and onto the concrete the load transitions from being a sheer load to being a bending moment that created the large tensile stress on the bottom surface, causing the panel to fail at the distance in from the end. Also of note, weight is not equal between the two rear wheels as it gets transferred once the suspension gets compressed by the difference in height, so closer to 2,000 lbs was applied, not 1275lbs. You could potentially measure the deflection of the truck suspension to get a more accurate measure of the applied load, and from the distance the concrete cracked at then be able to back calculate the tensile failure strength. The wire mesh in the middle of the panels should have little impact on this failure mode, but the addition of fiberglass to some of the panels will have a major impact on the ability to handle tensile loads on the bottom side of the panel.

[@giovannifiorentino8947]

To enhance the resistance the wire mesh should be place closer to the face subject to tensile stress (placing the reinforce closer to the outside face give additional protection against corrosion). Also a third light weight material could be expanded polysterene particles. It will be interesting to have a table that shows the strenght related to the thickness and lenght of the panels. Excellent job so far.

[@JohnAmerisun]

Would have been nice to see at the end of the video, or maybe after the aircrete one, a table of all the types of mixtures, with and without reinforcement grids / types, so it's easy to tell at the end of the video which one was better or at what levels they broke. Either way thanks for the info, love the videos.

[@farmingfromscratch]

Excellent work, thanks for taking all that time to do these tests, much appreciated.

[@mikenewman4078]

Thanks for the thorough investigation of home made concrete garden bed / fence panels. The takeaway I got was, they are plenty strong enough as built and Portland cement is just fine for the job. If anyone needed more strength then a loop around the indent would greatly increase the force required to initiate a crack in the face. The unwanted side effect would be a greater risk of concrete cancer. So, all in all it ain't broken, so don't fix it. BTW, I like your simple modular design. When I made a concrete raised bed some years ago, I bolted my panels together. It works well, but your design is more versatile.

[@jamesharrison3537]

I don't see how a loop would cause concrete cancer, but a lack of concrete cover to the reinforcement may cause spalling and reduce the life of the panel.The panels are not really thick enough to accept steel to modern standards, so the galvanised fence wire is a pretty good idea for being off the shelf.

[@Hjustk]

Man you are amazing, keep with the good work, hughs from Brazil!

[@lightdark00]

I would still love to see tensioned panels made. It would be the most expensive probably, but long-term peace of mind in extreme uses would be worth it.

[@1982MCI]

lightdark00 sure it would be worth it if this was a building panel but it’s sole purpose here is holding back 50lbs of potting soil from falling into a garden path. It won’t have any pressure against it at al so a tensioned panel in this application would be ridiculous Sorry our views don’t align but it’s just a garden bed. It would be a fantastic idea if we were talking about building a garden shed or a garage with similar panels but we aren’t yet

[@229glock]

Great series of tests and info....I should add, you're an impressively strong dude.

[@MANaboutTOOLS]

Thank you!

[@unitwoodworking5403]

It looks greatly strong enough to endure power and time endlessly . Great test and result.

[@boots7859]

Man, this is exactly what I've been watching this series for! You Sir with your testing and scientific methodology is starting to encroach on Project Farm territory. Loving this channel. How about trying to make a drywall form?

[@ImprovedEngineering]

At what depth you position the steel wire / mesh determines how much weight the panels can hold, essentially you want the steel to take all the compressive load. the surface that you are putting the weights (loading surface) on is in compression, aka added reinforcement is only for stabilization. I can draw you a engineering free-body diagram if need be to clarify. P.S. yes i'm a mech engr & i bought your old original plans but modified them a bit..

[@BillRobertsCatalyst]

would love to hear your thoughts on what ree and where best placed. Cheers Bill

[@lesshelton2607]

use a 2000 lbs hydraulic gauge from local parker dealer great video thanks you are a amzing

[@markusosterle3958]

I really appreciate all the effort you went through to try and get some accurate measurements to all the tests. Great job! Loved the video.

[@stephentrigg374]

Great videos and a lot of work, but I think you may have vastly underestimated the forces involved in ice formation in your tests. The upper limit if pressure required to prevent ice expansion completely is of the order of 1GPa (~10 atmospheres). Your truck parked on a couple of 2x4 segments may have hit 1MPa order of magnitude. The other limit - expansion - is about 1%. So you either have to expand by ~0.3% in each direction or survive ~1000 times your truck-test weight in pressure, or some compromise between the two extremes. In the real world, obviously lots of organic material in soil is compressible (as would be a stryrofoam lining to protect your plant's root from frost). So, it would be very interesting to see how they survive trough a winter when filled with soil and whether mulch etc, would be sufficient to prevent those catastrophic forces that ice can produce. New video in the spring?

[@DavidGalan777]

Great videos. You are so thorough and succinct, you could be Data's (Star Trek Next Generation) brother. Too bad he wasn't. He would be able to give you all the stats and precisely exact strengths by mental calculation.

[@MANaboutTOOLS]

LOL!!

[@laminap]

Love finding out great content is Canadian when I see a Mastercraft of Powerfist tool in the video!

[@boots7859]

Yep, a lot of quality YT content seems to be Made In Canada.

[@mackie4323]

His accent didn't gave him away? Aboat?

[@beartankoperator7950]

awesome man looking forward to the test with the aircrete hoping for at least half the weight great job with all of that lifting you just made me nervous when you stood up on those bags

[@earlliverseed1617]

That was great I was very surprised at the strength of the panels. The press with a different gauge is the way to go. Many Thanks

[@MANaboutTOOLS]

You're welcome. I was surprised by how much they flexed.

[@squib308]

Cool video - interesting. I've made various things with cement/perlite , which have come out variously good or not. I think the H2O/cement ratio was responsible for that. Aircrete panels next, that should be interesting.

[@g-lurk]

if 1/4 of a ton is 500lbs you'd think that the pressure gauge would have registered at least a little bit. then again the point load vs distributed load of the concrete bags may have played a role? i've listened to/watched almost a dozen of your videos and i think they're great. the narration is really solid and suitable for any time of day/mood

[@ITpanda]

A scale on one side of test system with a press or pulley would allow you to increase the load in s controlled manor while still allowing you to get a good estimation on the weight at which they failed.

[@kennethcruise7635]

THANK YOU FOR DOING ALL THAT WORK . i AM IMPRESSED .

[@MANaboutTOOLS]

Thank you too!

[@Mrbfgray]

These are *plenty strong* enough. However--as loaded they'd take even more if reinforcing wires were closer to the outside surface to take tension more effectively, obviously they must be made fairly quickly and you sure don't want wire showing on the surface so I wouldn't change much here. Very well done. (revisiting :D) May do my own version of this compelling design, the insets are crucial for aesthetics I think. Also 'scientific' enough Sir.

[@kellyj5610]

"Well, thats a fail." You only learn through failure. Every "failed" test is a learning opportunity.

[@MANaboutTOOLS]

True that!

[@minphang9351]

That's a well thought out and presented video. And you had a great workout doing it!

[@genegreear4183]

I would think that by adding even 2 - 3/8” rebar would be stronger than the he cattle panel. There is really not much steel even though it might hold the panel together better as a raised bed panel. Than a stress test. I really like your Chanel. I am thinking about lining a creek that flows through my twenty acres with some sort of a concrete panel that I can just add them as they are made sort of thing. I watching your tests closely to give me insight on how to build them and what mixes I might use. Thanks

[@alexanderdrakalski]

Great video. I loved how you tested the samples. The only suggestion I would make is that you test each of them to the point of failure to determine the tensile strength of each sample. That way you know which is strongest, which is weakest, and can place them in order of strength. Great work by the way. I was going to use treated pine or hardwood sleepers but will be adopting your method for my garden beds instead. I can buy concrete sleepers here but they are square-ended and cannot be joined they way yours do with the stepped end and hole for reo bar. Brilliant mate, just brilliant.

[@MANaboutTOOLS]

Thank you very much!

[@picayunebill6614]

Instead of wire in the middle try using galvanized rebar so it won't rust. i should dramatically increase increase load.

[@mansardmanor3869]

Looking for strength add #4 (1/2") rebar in the thickness area then add wire mesh 😊🤪 Great effort 👍

[@MANaboutTOOLS]

Thanks! I agree, rebar would make them stronger

[@mansardmanor3869]

@@MANaboutTOOLS gotta say, ❤️ love your ideas. Thanks 4 sharing 🤓

[@peterfitzpatrick7032]

The wire mesh is not helping at all (apart from holding it together after rupture) unless it is in tension... which it isn't , if it is not buried until it is offset to the front of the panel.... I like the idea of 2 strips of 1/2" rebar instead of the mesh ... but... the same applies, it needs to be in tension so buried deeper. Look at commercial lintel construction to see what I'm trying to explain. This is also why there is a right and wrong way to install a lintel. (A top & a bottom) Great vids btw... 😎👍☘️🍺

[@normgraham8630]

Your reinforcement grid, works on the other side of a pushing force. So, the reinforcement wire, should be closer to the bottom side, under the press. If your reinforcement is closer to the other side, you would get a very different result.

[@marietagorospe901]

I think the gauge on the hydraulic press did not register pressure because the panel flexed, much like using the bathroom scale over carpeting.

[@MANaboutTOOLS]

I was thinking about that too. But there must have been a force of at least 500 lbs or more to make it flex. I think the gauge is designed to read pressures way higher so it just didn't respond.

[@AJR2208]

These have been very good videos - Thanks for sharing them. They are Scientific tests though, and you have certainly put some effort into them. If you are aware of a term "Point Loading", then this is really what you have been testing. Michael & Haidee below was correct about tension and compression, but that is why reinforcing is introduced into concrete. Point Loading (surface area of load) is where your experiments have differed from the surface contact of the car tyre, to using one timber with the press and then increasing the point load with two timbers and your bricks. With full surface contact load when used to retain soil and I think that these will stand up to much larger forces. Well done!!

[@MANaboutTOOLS]

Thanks! And thank you for your comments here! Cheers, Kent

[@toastrecon]

This is probably obvious and intuitive, but the load calculation is about (b*(h^3))/12, where b=base and h=height. You'll notice that the strength is a LOT greater if you tested those beams in the standing up direction. It'd be a lot harder to do the test, but I guess it depends on what kinds of loads you expect the garden boxes to "see" during their lifetime. For example: if they're 2" x 8", laying down they'd have an area moment of (8 x (2^3))/12 or 5.33 if you stood them up, it'd be (2 x (8^3))/12 or 85.333 - note that this means that they could carry 16x the load in the standing up direction. If you were worried about loading in that direction, I'll bet you could maintain the same weight, but gain a lot of strength if you made "ribs" that ran the length of the form on the inside "soil side". You'd have to play around with the dimensions.

[@honeytubs]

So, if you knew the dimensions and if the wire reinforcement did not fail could you calculate the compressive strength of the concrete in psi? I know normally compressive strength is found by compressing samples until they fail. This beam test seems more feasible for someone who doesn't have equipment to generate thousands of psi.

[@falcor1969]

Hi Kent. Instead of using wire mesh, use 12 - 16 mm deformed bar with 2 or 3 lengths running lengthwise along the panel and evenly spaced across the panel. This should increase its strength quite substantially. Wire mesh is good for keeping concrete together, but it doesn't really add any strength to the concrete. Rebar or deformed bar does add strength. Consider any structure which requires additional strength, such as pillars or concrete wall etc., the use of rebar is essential. Mesh is good for concrete pads, footpaths or driveways. Your panels lie vertical, not horizontal. The forces of the dirt within the four panels is minimal however, rebar for added strength is the way, and not mesh.

[@geoffb108]

I would like see a test of one made without the steel reinforcement and maybe one using fibre glass additive

[@gc0009]

even though the panels have broken, I still think it's worth using the lighter versions as planters. because they wouldn’t be moved often or thrown up and back and forth.

[@tealkerberus748]

Considering the other materials people make planters from, I think these would be plenty strong enough. Roofing iron with pine framing seems to be very common - and the problem that concrete addresses is not breakage, but rust and rot.

[@Bowlsy1989]

You must take in to consideration point loading which is rare for purposes, all tests where based of this. Mpa test is most accurate Eitherway definitely proven strength 👍

[@littlestflyable]

I don't think it can be considered a sideways load of you're putting all the weight in the center. I think if you distribute the weight more evenly you'll be able to put more weight on. But, I think that will cause the pin joints to fall. You should test a solid one without a pin joint. When the joints are connected they will be stronger and that will show a true test.

[@Ranchpig67]

Problem with all of your tests is that you're not using uniform applied pressure. The truck tire was not only heavier but had the smallest foot print or maybe close to the block under your press. The bottom line is those things are all insanely overkill for a garden box. You could probably make them 1" wide and have plenty of room for any soil expansion. So here's an IDEA. Make your forms with a channel on the inside. 1" thick or so, and a 1 or 2" Tee, like half an I Beam. That would keep them from bulging and I'd assume they would be in the 20lb range for the 36" panels. You could still use 1/2" flexible tubing that you could pry out after cement set for your connecting bar. You wouldn't need any PVC.

[@FatLaughingBuddha]

I disagree that this isn't scientific - you're doing awesome citizen science, keep it up!

[@MANaboutTOOLS]

Thanks!

[@adrumwhisperer]

It seems like for garden beds all of the options are strong enough so it comes down to three decision points.... cost, weight and time. The extra effort of aircrete saves weight, but needs wire reinforcement. Portland cement is strong enough and cheaper than CSA. CSA would save in curing time. Would you agree with this summary? The lowest effort and cost option seems to be portland cement without wire reinforcement, Have you tested this option?

[@MANaboutTOOLS]

I'd say the simplest and easiest is regular concrete mix from any big box hardware store. But I'd still add some wire mesh. It too is cheap and easy. Also, have a look at my super simplified form: kzbin.info/www/bejne/b5zKkmygiKxqfdU

[@ejrupp9555]

@@MANaboutTOOLS it seems you have the wire mesh in the top portion so it is doing nothing for this test other than holding the mass together when it cracks. The large rectangular relief facing the ground is the bottom of your form correct? You placed the wire just under the surface on the non relieved side right? It would fare better in your tests had you just put the wire on each side of the relief 3/4ths inch from what would be the face. Or you should have done the test with the relief facing up. The wire should be at the bottom (closest to the ground) to counter tension. For the intended purpose, wire should be used in just the bottom, so if your orientation of the panel is for a planter box, just put it in the area that will be near the ground. Since aircrete absorbs water easily, the fiber is practically necessary to stop freeze/thaw cracking. Adding a bit of lime will also help freeze/thaw issues but will make the cure time longer and you have to make sure it stays wet longer ... 2 days minimum. Hey maybe you could test ratios ...

[@LouisFPak]

Great channel! Thank you! Hot/Cold expansion and contraction in geographic locations must also be a factor? Without frost ground heaves concrete is very stable. Also damp soil is fine down south around your project. But up north, it's big trouble when it freezes (as we all know) Thank you for a great channel!

[@MANaboutTOOLS]

Thank you very much!

[@flick22601]

Kent, you're doing great work. How long did you allow the panels to cure before running these tests? I believe that 28 days is the normal period for concrete to achieve its engineered strength.

[@martamccool2740]

Strong enough for garden purpose , is my opinion

[@jasonhinson3812]

I’d like to see a thinner piece tested for impact resistance…….such as a equivalent to 3.5” hail. Would be nice to make roof tile out of if it will support the weight of a roof installer and is impact resistant

[@efrenhaw]

Great video! Thank you for the great work you put into this

[@XX-kf7mx]

I appreciate your efforts. Keep up the good works

[@denisok888]

Very scrupulous work👏! Thank you

[@tinaleanne8230]

Excellent empirical testing procedures, even if going in with assumptions the testing was not based on the assumptions. Unfortunately, test results based on a single sample is not conclusive. I assumed the lava rock would fail first and the 'regular' mix would not fail under equal testing parameters. I was certain the truck would kill any of them. No to find your others so I can find the mixing ratios used.

[@shareyourchristmas]

Thank you for the post

[@halfgrassgardener5060]

The fact that you never gave up on your goal. Not once did I see you scratch your head. You simply accepted change.

[@penname8380]

Watched til the end. Good stuff.

[@drewjohnson7863]

Your results are consistent with engineering principles. If you examine large flat roof building trusses, such as across a gymnasium, you'll find that the center has to be the strongest part of the truss. Keep up the great work.

[@druida6970]

I liked the content of your channel. I'm following from Brazil

[@pablocruz62]

I thought a string line or laser level might be nice to see how much if any flex. I am starting with aircrete myself and thinking of adding ash from the fire place.

[@MANaboutTOOLS]

That's funny. I was thinking that during the editing of this video. I had the additional low angle camera and I could superimpose a line over that shot. I'll try that for the aircrete panels I'm testing next.

[@NepticFathers]

Possibly mixing in cut up high pound fishing line could be an easy way to improve tensile strength

[@tealkerberus748]

You can buy plastic fibres for the purpose. They look like concrete broom bristles - fairly stiff plastic with the sides deformed enough to grip in the concrete. I think fishing line wouldn't have enough grip.

[@albyadityarachman1858]

Great man, so humble 🙏thx

[@loneforest6541]

very useful info...thanks for sharing

[@MANaboutTOOLS]

Thanks!

[@TheRedneckprepper]

I think you were looking for a work out ? brother ya got one i dont see any reason to test the load on a vertical plane ! but i was cool ! TY

[@MANaboutTOOLS]

I laid the panels that way as many viewers asked how they would take a severe winter. Wanted to simulate a force against the inside face of the panel.

[@ssamd263]

I’m more concerned with whether the panels can tolerate freeze thaw conditions which is what would happen here in Maine. Also I wonder what the forces would be like when soil freezes that is contained by the boxes. Thanks for some great Ideas for making boxes and I hope to be making fence posts which need to be at least 8 feet long.

[@MANaboutTOOLS]

All the panels I have made have endured many, many freeze/thaw cycles. No issues yet.

[@pablocruz62]

I would think that at s quarter ton they would hold up Great, being as its not an enclosed space. I wondered about water getting in the concrete and failing it that way.

[@billbucktube]

Good work.

[@ellarry5519]

Could you test a couple panels with the face facing up instead of down. It seems as if the reinforced wire mesh its a little more towards the back side, I think it will be stronger with the face up