Dry pour concrete - An Experts Opinion Dry pour concrete slab details

Check this video out where I did tested dry pour concrete https://youtu.be/YPAKzrv39xM Warning! The results are surprising.

This has to become an Oklahoma State research project. We need slabs to core and beams (reinforced and unreinforced) to break to see how it compares to standard concrete mixed per the manufacturer - this could be a whole series that either debunks the practice or identifies some best practices and recommends where to use it.

I have never nor really plan to pour concrete. But I love your channel for the practical science and the deep knowledge of the subject.

This seems closer to the super dry mixtures used for roller compacted concrete, or dry pack used under a lot of tile jobs. It would be interesting to see if you could densify it with some type of roller or a vibrating compactor.

Excelent video. Objective and rational. Great summary of pros and cons. Now the testing can start.

I've placed concrete with traditional and dry pour methods. I think dry pour has its place in a few scenarios, but those few scenarios cover quite a bit of the applicability of concrete around residential houses. Dry pour is so much cheaper for typical slabs, coming in at about 30% of concrete contractor bids and it's taking off because homeowners are being priced out of simple projects by today's wet pour prices. Some dry pour test ideas are: -Strength tests using quality methods that provide unbiased results for typical 4" to 6" flat pours. -Can the mix be compacted during placement, and is that a benefit? Anecdotally I've noticed that we can compact dry pour mix with foot traffic during placement. My gut tells me that's likely a beneficial action but a test would indicate whether there's an actual benefit. -What is the adherence of dry-poured concrete to reinforcement steel as compared to wet pour? Is it adequate? An aside on steel, I think dry-pour concreters do a far better job at centering rebar in a flat pour. Nearly all residential pours have "hooked-up" rebar or mesh, and that's of little or no use. Placing steel in dry pour is amazingly simple, and you don't need chairs and almost no wire tying. You place half of the dry mix, smooth the surface, place one direction of steel, seat it in the dry mix with foot traffic during placing, place the other direction and apply more dry mix to hold it, and nothing moves. No wire, no chairs, no tying labor. -Installers can perform limited but noticeable compaction to the dry pour during placement using common foot traffic. Does material compaction make a difference? -How do dry pours perform in freeze-thaw tests? Does dry pour need a permanent sealer applied to it? -Is it better to begin misting dry pour just after sunset and water through the night? (I haven't figured out how to cover the dry pour during initial misting without marking the surface) -Is use of a mortar mix as a thin layer of surface ok, or does it create a potential spalling layer? -Is there a practical method to create a smoother, more polished surface than what is achieved by the paint roller finish method? -What is the practical limit of dry-pour slab depth? If a person is pouring a 4" slab but wants a footing (8", 10", etc.) around the perimeter, can this reasonably be achieved? Does thickness of the slab affect final strength when using typical dry pour wetting methods? Thanks!

Great Video! We did an 8'x6' slab outside our back door in late August of this year. Hottest most humid day of the year too. We didn't follow the Cajun Country Family videos exactly because we are in MN and used rebar and I wanted a stronger base with some sand and class 5 based on what I do for a living and am used to seeing. Was it necessary to put in a base or could we have done it directly on grade? We also did way more than 4 sprays because in our 1'x1' test pour the water didn't go all the way down and it was just the bag mix. So we misted twice as directed and then sprayed every hour for maybe 12+ hours and then at least 3 times a day for 6 days all while curing it with plastic for the typical 7 day wet cure. The plastic staid pretty wet and we could see the moisture disappear into the mix. No cracks yet and feels solid! We are having some slight surface scaling. Not terrible, but our dog runs off of it and his claws leave little marks on the surface. Any thoughts on following just the 4 sprays vs. what we did to prevent scaling of the surface? We are hoping to do more pours next year as it only cost us ~ $300 for the nice size slab (because of the base we used. Would be cheaper if we just put the dry mix on the dirt). It is so much nicer than having dirt outside our back door and we hope to do a few more after the spring to see how it held up through the freeze/thaw of a northern winter.

I've used dry mix concrete technique for femce and gste posts for decades...... my technique includes wetting the adjacent dirt well prior to dumping in the bagged concrete. My train of thought is that the concrete wants water, and I want good concrete. So i provide starter water in wetting the dirt that is gong to come in contact. MrEric

Dr. Ley- Thanks for finally dipping your toe into "dry pour" concrete. I understand your biases lean toward commercially processed concrete, but you made several critical assertions of dry pour in this video that should be fully tested to confirm. I refer to your remark that dry pour will not achieve similar performance to wet pour, I infer your contention is related a less homogenous mix with dry relative to wet process. I think, however; we all would agree that overwatered wet pour, mixed "in the wild", underperforms , probably due to large aggregate migration "to the bottom" of the pour. The "curing" of cement + aggregate into concrete is a chemical process, it requires "adequate" hydration to proceed to full "cure" at about 30 days under normal circumstances. The "Cajun Country" hydration regimen is not scientifically derived, it empirically seeks to stabilize the slab "top crust" and hydrate the slab for cure promotion. It could probably be simplified into a 2 step process; first, crust stabilization could probably be achieved with 2 mistings at 10-15 minutes apart, and second, the timing of hydration soaking is less relevant, as long as the top of the slab stays moist or wet the slab will hydrate quickly (see video from renetto for visual evidence). You refence "air voids" as a problem in dry pour, but if you might research a quantity of dry pour videos, you will find people have addressed this issue by, for instance, impacting the dry forms with a rubber mallet prior to or after screeding and before wetting, yet another ingenious fellow attached a palm sander to the screed board attempting to achieve a smoother surface. This is probably adequate for small projects up to 4'x4', I would guess. Your critique of dry pour lacking "air entrainment" for freeze/thaw protection warrants merit, but where do "air voids" end and "air entrainment" begin. As I peruse the comments attached to this video, I am struck by the high percent of commenters requesting "testing" of dry versus wet pour methods. The the video testing of dry vs wet here on YouTube is not scientific, and often "tests" concrete that is not yet fully cured with methods that are "empiric" but not "quantifiable". Since you have access to the required lab equipment, might I suggest the following tests. It would be most helpful to the DIY community to know how dry and wet pours compare with regards to cure time, final strength, and density (permeability). At a minimum; a comparison of dry pour versus wet pour with big box bagged dry concrete mix at 3,7, and 30 day interval testing, a bonus would be to add samples of commercial mix (from truck or yard) with similar specs. Your assessment of the final quality (compressive strength, density, and air entrainment) of concrete produced by each method would be highly valued by all who follow this channel. Afterthought: perhaps you might run a few samples of concrete prepared with both PLC and straight Portland to see which might be a better choice for the small batch DIYer who might seek to add fiber to a bag mix or self mix with a small portable mixer, and still dry pour a small slab. We appreciate your efforts and insights!

Thankyou for this Tyler 👍

What are your thoughts on it if say you were doing a 4" slab and put 2 inches in the forms and do the water things then add the final 2 the next day? More penetration?

I need a slab to park my trailer on when it's not being used. It's a 5 x 8. Could a dry pour work or should I use a mixing type?

Very kind delivery. So this method is not to be used for structural concrete, but has its place.

Great video...always learn something...concrete rules

I saw you on a Sunday Morning segment today and I am waiting on delivery of 24 bags of concrete to pour a 4X8 slab in front of a French door. I have done a fair share of concrete for a DIY er and I spent time in construction but I am 77 now and this job is in a resort town where it’s difficult to get people and its expensive. I agonized over this and finally decided to give it a try. I feel much more confident after your video please do more research. I have more projects.

Do you have any videos on Hybrid ECC using the Helix Steel 5-25 TSMR and trying to find a optimized mix cost wise? I am trying to learn as much as I can about ECC, but having difficulty. One area especially hard to find info on is the fire resilience of ECC.

I plan on dry pouring a shed floor. Not a lot of weight on it, and it won't have to support vehicle travel. For this purpose, seems like a great and cost saving idea. Thanks for the info.

So what is the objective relative strength of a little dry pour slab?

can you make dry-pour test cylinders and crush them please? i need to know the psi grade compared to what the wet mix of 3500psi sakrete. can you test a 8"-12" thick footing that is dry-poured 40"-50" below grade, left for 28 days and dug up again? everyone is testing the dry pour slabs that are misted every 1h, but what about dry mix that is just in contact with soil and left for a while. there's got to be a difference.

haha, I guess I've been waiting for this video since I learned about dry laid concrete