# concrete was allowed to dry with out misting.



## de-nagorg (Feb 23, 2014)

The need for misting depends on the temperature that day, the rate of evaporation, and direct sunlight heating the surface, as well as other factors , humidity, wind speed. etc. 

After this time, it is as cured as it is getting, it might cure a little more, but not noticeable.

It is fine if it looks uniform in area color. 

And watering it now is a waste of time.


ED


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## JCunningham (Jul 26, 2019)

thanks that what i thought. My brother put a box fan blowing over it. i turned that off 3 days later. its been mid 70s-low90s and 60-80% humidity. No direct sunlight. garage stays about 10 cooler then out side temps. the concrete is white and uniform.


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## de-nagorg (Feb 23, 2014)

I would call it good enough, and install the lift assembly. 

ED


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## JCunningham (Jul 26, 2019)

thanks


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## stadry (Jun 20, 2009)

*you friend doesn't really understand concrete,,, 'misting' isn't required to properly cure concrete however it IS 1 method to allow proper & acceptable curing,,, think you'd see garden hoses stretching 1 mile along a freshly placed conc highway ? ? ? same w/sidewalks & driveways*


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## Yodaman (Mar 9, 2015)

As I understand it, anything you can do to slow down the curing process is a plus. It helps to prevent cracks and ultimately provides for stronger and harder concrete.
Since you are inside a garage, fast drying from wind and sun should not have been an issue. Although placing a fan on it was a mistake IMHO, 
Concrete reaches 70% of it's ultimate strength within the first few days and full strength in 28 days.
https://www.nrmca.org/aboutconcrete/cips/11p.pdf
https://precast.org/2013/10/28-day-myth/


If it were mine, I would be OK installing the lift after a couple weeks, but I wouldn't put a car on it for at least 28 days.


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## HenryMac (Sep 12, 2018)

JCunningham said:


> Im installing a max jax M6 lift and the floor in my garage was done to thin (2" with a gap under it because they didnt compact the gravel) so I had my brother who is in construction cut 2 4'x4' squares. We used 20 bags of Quickrete 5000psi 80lb premix. He poured it 7" thick. 2 weeks go by and im taking to a friend who tests concrete for a living and he said you have to mist it for it to cure properly. We did not do that. Is it too late? I would guess so. what if i put water on it now 2 weeks after its been in the 80s?
> The lift requires 4" of 3000psi.


Not sure where you received your retrofit information but it seems inadequate to me.

The lift requires a 4" thick slab in the building. If the slab isn't 4" then a retrofit is needed and when retrofitting a slab for a 2 post lift you should know that the new concrete needs to be doweled into the existing slab. And before installing the new concrete ensuring the sub-grade is properly compacted is critical. Additionally, who told you 7" was an adequate thickness? Did you place any re-bar in the new retrofit.

Most folks retrofit using one new piece of concrete that spans the complete width of the vehicle as shown below.


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## HenryMac (Sep 12, 2018)

.............


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## JCunningham (Jul 26, 2019)

yes we used re bar doweled into the existing. no one told me 7" we just ended up that deep. we did it this way because we saw someone else that did it this way but they did 36"x36" and not as deep.


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## HenryMac (Sep 12, 2018)

I ran some numbers... Any vehicle on the lift heavier than 2,000 lbs and the only thing keeping the lift columns / concrete from tipping are the rebar dowels.

Since your existing slab is only 2" thick you should consider abandoning the installation of the lift unless you demo out the concrete and replace it with a single retro pad that goes all the way from one jack column over to the other, as detailed in my previous thread above.


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## HenryMac (Sep 12, 2018)

And one last thing. The sub-grade material on which the new concrete is to be poured needs to be compacted and tested before pouring the concrete.

More on that here: https://www.garagejournal.com/forum/showthread.php?t=346747&highlight=proctor


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## Nealtw (Jun 22, 2017)

So if the concrete completely crumbles, where wit it go? Down? If it doesn't completely crumble and goes down, that is a problem with the soil under it. 

The weight of the car has not changed from when it sat on four tires on the slab with only four small foot prints.


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## HenryMac (Sep 12, 2018)

Nealtw said:


> So if the concrete completely crumbles, where wit it go? Down? If it doesn't completely crumble and goes down, that is a problem with the soil under it.
> 
> The weight of the car has not changed from when it sat on four tires on the slab with only four small foot prints.


Your analogy is proper if the OP was installing a 4 post lift. He is not. 

A Max Jax is a short 2 post lift with no overhead beam between the columns. This type of 2 post lift induces totally different loads into the concrete than a 4 post lift.

What we are trying to avoid with this 2 post lift is shown visually below. It happens... it's real.


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## JCunningham (Jul 26, 2019)

well thats just ****ing great $400 in the garbage. probably going to cost me another $1000 to install this little lift. so probably around $3500 to put a mid rise lift in because some piece of **** did the floor wrong. not worth it at all.


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## Nealtw (Jun 22, 2017)

HenryMac said:


> Your analogy is proper if the OP was installing a 4 post lift. He is not.
> 
> A Max Jax is a short 2 post lift with no overhead beam between the columns. This type of 2 post lift induces totally different loads into the concrete than a 4 post lift.
> 
> What we are trying to avoid with this 2 post lift is shown visually below. It happens... it's real.


Did that photo come with a report, perhaps bolting it to asphalt was not the best idea.


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## JCunningham (Jul 26, 2019)

actually that pic of the lift shows the studs failed not the concrete.


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## JCunningham (Jul 26, 2019)

you never put a lift in asphalt


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## JCunningham (Jul 26, 2019)

this is what i was going off of


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## JCunningham (Jul 26, 2019)

HenryMac said:


> I ran some numbers... Any vehicle on the lift heavier than 2,000 lbs and the only thing keeping the lift columns / concrete from tipping are the rebar dowels.
> 
> Since your existing slab is only 2" thick you should consider abandoning the installation of the lift unless you demo out the concrete and replace it with a single retro pad that goes all the way from one jack column over to the other, as detailed in my previous thread above.


so your saying it will fail at 2000lbs lifted


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## Nealtw (Jun 22, 2017)

HenryMac said:


> I ran some numbers... Any vehicle on the lift heavier than 2,000 lbs and the only thing keeping the lift columns / concrete from tipping are the rebar dowels.
> 
> Since your existing slab is only 2" thick you should consider abandoning the installation of the lift unless you demo out the concrete and replace it with a single retro pad that goes all the way from one jack column over to the other, as detailed in my previous thread above.[/QUOTE
> 
> ...


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## JCunningham (Jul 26, 2019)

its only going to tilt in


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## Nealtw (Jun 22, 2017)

JCunningham said:


> its only going to tilt in


There is nothing to do to a car to change the front and back balance out while the car is up?


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## JCunningham (Jul 26, 2019)

so what do you think i need to do this HenryMac? 4'x14' 6' deep with re bar?


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## Yodaman (Mar 9, 2015)

I read over the install manual, and it is kind of vague as it pertains to foundation requirements when the main floor is too thin.
Personally, pinning the new pads to the 2" thick existing slab would not give me much confidence. After you drill a 5/8 or 3/4 hole in a 2" cross section, the remaining web thickness is mighty thin.
I would call the MFG, and get a better explanation of the foundation requirements.


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## SPS-1 (Oct 21, 2008)

Yodaman said:


> I read over the install manual, and it is kind of vague as it pertains to foundation requirements when the main floor is too thin.
> Personally, pinning the new pads to the 2" thick existing slab would not give me much confidence. After you drill a 5/8 or 3/4 hole in a 2" cross section, the remaining web thickness is mighty thin.
> I would call the MFG, and get a better explanation of the foundation requirements.


Not so vague: It says _Do not attempt to install this lift if you have never been trained on basic automotive lift installation procedures. Reference ANSI ALI ALIOM requirements for installation and service of automotive lifts._

Its worth the $20 to buy the standard, but not sure how specific they are going to be. Its also worth the the time to phone the manufacturer. They probably get calls like this all the time. But they likely will be careful not to try to engineer your foundation over the phone. 

Gotta say, the big one piece foundation like HenryMac shows on post #8 looks a lot more suitable than two independent pads.


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## Yodaman (Mar 9, 2015)

SPS-1 said:


> Not so vague: It says _Do not attempt to install this lift if you have never been trained on basic automotive lift installation procedures. Reference ANSI ALI ALIOM requirements for installation and service of automotive lifts._



Yea, that sure sounds like a CYA statement. Their customer base is home owner DIY mechanics. So expecting the home owner who purchases their product to be trained in lift installation is a bit of stretch. I doubt it would hold up in a liability court.


I just re-read their specs, it does say a SOLID 4" slab. I would still be calling them.


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## SPS-1 (Oct 21, 2008)

I found another manufacturer that specifies minimum 149" wide slab. So two footings would not be acceptable in that case. They also said minimum 4" thick, but also noted 6" thick was preferred. If I were working under that lift, I would not appreciate knowing the footing was targeted to minimum standards.


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## Nealtw (Jun 22, 2017)

I went looking for loads on the footing with a single post with a cantilever load on a beam. I was quickly reminded why, if you can not follow the instruction to the tee, you should consult with an engineer.


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## JCunningham (Jul 26, 2019)

i emailed them this I purchased one of you M6 lifts and then found out my garage floor is only 2" thick. what would be the minimum i would have to do to install my lift. thanks

and there reply was this 

Hello J***,
concrete thickness needs to be 4 inches minimum. Rebar/steel reinforcement is necessary for all lifts
ill email them back


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## Nealtw (Jun 22, 2017)

JCunningham said:


> i emailed them this I purchased one of you M6 lifts and then found out my garage floor is only 2" thick. what would be the minimum i would have to do to install my lift. thanks
> 
> and there reply was this
> 
> ...


They will be real careful while they give you non answers. They have already covered there ass by saying 4" when most garage slabs will be between 3 and 3 1/2" with no mention about what should be done when the floor is not 4"


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## JCunningham (Jul 26, 2019)

i just looked at the concrete that was cut out. its 3 1/2" to 4" thick. we tested in 2 different locations. then i decided i wanted it in a 3rd location and we cut. I wasnt there when my brother dug out the holes.


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## Nealtw (Jun 22, 2017)

Do you have access to a trailer you could load up to be heavier than the car to test it out with out risking the car.


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## JCunningham (Jul 26, 2019)

a friend of mine has a car trailer


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## JCunningham (Jul 26, 2019)

o my sisters boyfriend has a 90 something ford explorer thats junk but moves i could try it with that.


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## de-nagorg (Feb 23, 2014)

It's going to be fine, hold up well. 

Do not let the naysayers get to you, and petrify you with fear. 

But do test it every time before getting under any lifted vehicle, even that little loader in the picture. 

lift the vehicle, walk around it and gently shake all four corners, to see if anything gives, and if solid, proceed with your repairs. 


ED


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## Yodaman (Mar 9, 2015)

Probably wouldn't be a bad idea to keep a set of stands under the vehicle when you are under there. Assuming the footers hold well, mechanical equipment does occasionally fail. 

I would always cringe seeing guys work under their cars in a dirt driveway being held up with a bumper jack! :surprise:


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## de-nagorg (Feb 23, 2014)

Yodaman said:


> Probably wouldn't be a bad idea to keep a set of stands under the vehicle when you are under there. Assuming the footers hold well, mechanical equipment does occasionally fail.
> 
> I would always cringe seeing guys work under their cars in a dirt driveway being held up with a bumper jack! :surprise:


 I bear a few scars from such an adventure, 43 years ago. 

I now make darn sure that I have plenty of support under any vehicle that I need to get under. 

I mentioned this before, but it warrants repeating, I had a Car jacked up in a snow bank, working on the steering assembly, ball joints, tie rods, and such. 

The sun came out and melted the ice under my jack, it slipped, and the car came down on my head, I am now blind left eye, deaf left ear, a hole the size of my thumb above my left ear, no skull. 

I no longer trust just a jack, but I would trust his system, after doing the walk around, shake it, and test it, before getting under one. 


ED


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## JCunningham (Jul 26, 2019)

I have 4 2500lb 29"-49" lift jack stands https://www.zoro.com/sumner-v-head-...xactTarget&utm_medium=Email&smtrctid=87784061 and I always shake the car befor i get under it.


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## HenryMac (Sep 12, 2018)

JCunningham said:


> well thats just ****ing great $400 in the garbage. probably going to cost me another $1000 to install this little lift. so probably around $3500 to put a mid rise lift in because some piece of **** did the floor wrong. not worth it at all.


Well... the folks at Max Jax, and pretty much most lift companies, should have better information for their customers regarding the slab and how to retrofit for a lift.

They don't because from a marketing standpoint it turns away customers.

Mohawk is the only one I know of that actually has good data.

Keep your chin up JCunnigham.... one of the best purchases I ever made was my Rotary Lift. Bought it in 2007 and it's a time and back saver.

Good luck to you sir.


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## ddsrph (Nov 23, 2013)

When pouring and curing concrete I have read that you can get up to 50% more strength by keeping it wet during cure for 7-10 days. Like previously mentioned this can be impractical in many cases. I always use a clear cure and seal sealer applied as soon as the concrete
sets (same day as pour). I am mentioning this mainly to get opinions from the pros rather than offering advice.
Thanks
JM


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## A Squared (Dec 19, 2005)

Nealtw said:


> Did that photo come with a report, perhaps bolting it to asphalt was not the best idea.


I'm pretty sure that is dirty concrete, not asphalt. 



JCunningham said:


> actually that pic of the lift shows the studs failed not the concrete.


That's correct, but I think the point of posting the picture was to illustrate that 2 post lifts generate completely different loads on the slab than the car sitting on it's tires, or even double the car's footprint. Sitting on it's tires, the car only generates compressive loads, applied straight down. The lift generates moments (twisting loads). If it was just compressible loads, the anchors wouldn't have failed in tension (pulling).


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## Nealtw (Jun 22, 2017)

A Squared said:


> I'm pretty sure that is dirty concrete, not asphalt.
> 
> 
> .



I was comparing it to the concrete in the picture and the anchor bolts were never set in concrete or he would not remove them by hand.


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## ddsrph (Nov 23, 2013)

I am not an engineer but I would consider renting a concrete saw and dig a trench from one post to next two feet or so wide and as deep as you feel necessary. Then dig a similar trench teeing into this midway between posts running under car. Rebar heavily as you deem necessary then pour the concrete tee.


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## A Squared (Dec 19, 2005)

Yodaman said:


> As I understand it, anything you can do to slow down the curing process is a plus.


Slowing the process isn't really the main purpose of keeping it moist during curing. Curing is a chemical process, and one of the chemicals needed in that process is water. Once all the water in the mix is used up by the chemical process and by evaporation, the chemical process of curing stops, and the concrete stops getting stronger, even though the mix of cement and aggregate *could* get stronger, it doesn't. Because it's out of water. Making sure that the concrete doesn't dry out during the curing process helps ensure that there's enough water present so that the chemical process of curing will keep going. 



Yodaman said:


> It helps to prevent cracks and ultimately provides for stronger and harder concrete.


 The chemical reaction of curing generates heat (like a lot of chemical reactions) and that heat can cause the curing process to speed up, which can cause cracking in the concrete, so misting can be used to cool things off which keeps it from curing too rapidly. So it's not that your wrong about slowing down the curing process, exactly, just that that's only one of the things that water does. When they were pouring the Hoover Dam (which was huge pours, one on top of another) they embedded pipes in the forms and pumped chilled brine through the pipes to carry off the heat generated by the curing. 





Yodaman said:


> Concrete reaches 70% of it's ultimate strength within the first few days and full strength in 28 days.
> https://www.nrmca.org/aboutconcrete/cips/11p.pdf
> https://precast.org/2013/10/28-day-myth/


Concrete doesn't reach full strength in 28 days. That's explained in the second brochure you linked. 28 days is an arbitrary benchmark for testing, and design requirements are written around that benchmark, so it might be accurate to say that it reaches it's full design strength in 28 days. But the curing process is properly controlled, it's not allowed to get too hot or freeze, and there's water present in the concrete, curing will continue (and the concrete will continue getting stronger) long after 28 days.


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## A Squared (Dec 19, 2005)

JCunningham said:


> its only going to tilt in


Not necessarily. Unless you have the vehicle places so that the center of gravity (balance point) is exactly at the posts, there's going to be some fore or aft moments (tilting forces)


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## A Squared (Dec 19, 2005)

Nealtw said:


> and the anchor bolts were never set in concrete or he would not remove them by hand.


I'd agree that they aren't J-bolts set when the concrete was poured. Given the relatively new appearance of the lift, and the relatively old appearance of the concrete, they were almost certainly some kind of retrofit bolts set into holes drilled into the concrete; wedge anchors or something similar. 

Anyway, the picture is a good illustration of the fact that there are ways for a lift installation to fail.


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## HenryMac (Sep 12, 2018)

HenryMac said:


> I ran some numbers... Any vehicle on the lift heavier than 2,000 lbs and the only thing keeping the lift columns / concrete from tipping are the rebar dowels.
> 
> Since your existing slab is only 2" thick you should consider abandoning the installation of the lift unless you demo out the concrete and replace it with a single retro pad that goes all the way from one jack column over to the other, as detailed in my previous thread above.





JCunningham said:


> so your saying it will fail at 2000lbs lifted


No, I'm saying the only thing keeping it from tipping is dowels drilled into 2" thick concrete. 

Which is scary as hell IMO.



JCunningham said:


> so what do you think i need to do this HenryMac? 4'x14' 6' deep with re bar?


If I were you, I'd send the Mohawk retrofit concrete detail to MaxJax, tell them again the slab your doweling into is 2" thick, and ask them if the Mohawk specification is acceptable for their lift in your situation.

If they tell you the 4" concrete and re-bar line again, ask them how big that concrete slab needs to be and ask for the detail of the re-bar layout.

If they won't agree in writing, signed and dated, that it's acceptable or won't send you a specification in writing, signed and dated, of how big the slab and re-bar configuration has to be I would hire a structural engineer to come out, evaluate your actual site, and then provide you with a drawing and written specifications, signed and dated, of what you need to do. Which of course should include compaction test on whatever sub-grade materials you end up using, like I linked to previously.

Following the above you will end up with a written and signed document telling you how to proceed.... rather than trusting your life to what some folks (like me) on an internet forum think.

Good luck with your project. :wink2:


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## Nealtw (Jun 22, 2017)

@*HenryMac* Did you see that the OP has the waste concrete that came out of the hole and it seams that where the holes are the concrete was as much as 3 1/2 to 4" 

post 32 or there abouts.


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## HenryMac (Sep 12, 2018)

Nealtw said:


> @*HenryMac* Did you see that the OP has the waste concrete that came out of the hole and it seams that where the holes are the concrete was as much as 3 1/2 to 4"
> 
> post 32 or there abouts.


Thanks Neal. I did read that and saw where he measured one piece and it was 3-1/2". Like you stated previously most slabs are 3-1/2" (2 x 4 height) and thinner. I've seen, as I'm sure you have, slabs vary from 1-1/2" to 4"... piss poor work. 

At our last home I made a contractor re-grade our driveway sub-grade before pouring. It measured 3-1/2" max, I specified 4" min., the contract said 4". We went around and around, in the end, he re-graded it. 

The bottom of the slab shouldn't vary more than 1/4" if it's done by a reputable company. And flatness of the bottom of the slab is just as important as the top when it comes to stresses in the concrete.


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## Nealtw (Jun 22, 2017)

HenryMac said:


> Thanks Neal. I did read that and saw where he measured one piece and it was 3-1/2". Like you stated previously most slabs are 3-1/2" (2 x 4 height) and thinner. I've seen, as I'm sure you have, slabs vary from 1-1/2" to 4"... piss poor work.
> 
> At our last home I made a contractor re-grade our driveway sub-grade before pouring. It measured 3-1/2" max, I specified 4" min., the contract said 4". We went around and around, in the end, he re-graded it.
> 
> The bottom of the slab shouldn't vary more than 1/4" if it's done by a reputable company. And flatness of the bottom of the slab is just as important as the top when it comes to stresses in the concrete.



But he does have lot more than the suggested 2" so it is not failure for sure , now it's just a maybe. :smile:


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## HenryMac (Sep 12, 2018)

Nealtw said:


> But he does have lot more than the suggested 2" so it is not failure for sure , now it's just a maybe. :smile:


No maybe at all. The specification is minimum 4", per manufacturer. So it's a failure at anything less than 4". Not to mention the fact that the OP has no idea at all what psi concrete he actually has. And if it varies from 2" to 3-1/2", whoever poured it has questionable quality.

And mixing concrete up in a wheelbarrow is also a crap shoot. He needs to have a mix plant send a truck out, and check the mix sheets before the pour.

Trust.... but verify.

But you knew I'd say that.


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## A Squared (Dec 19, 2005)

Nealtw said:


> @*HenryMac* Did you see that the OP has the waste concrete that came out of the hole and it seams that where the holes are the concrete was as much as 3 1/2 to 4"
> 
> post 32 or there abouts.



True, but he also mentioned that the base underneath the slab was inadequately compacted and had subsided from the underside of the slab as much as 2 inches. That's an additional level of complication.


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## A Squared (Dec 19, 2005)

Nealtw said:


> so it is not failure for sure , now it's just a maybe.


"just a maybe" isn't very comforting when we're talking about failure of something holding up 3000-4000 lb over my soft squishy body.


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## Nealtw (Jun 22, 2017)

A Squared said:


> "just a maybe" isn't very comforting when we're talking about failure of something holding up 3000-4000 lb over my soft squishy body.


Yup, is there a better word? It is still better than probable. I think like was suggested earlier, testing with a heavier weight would be my thinking.


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## HenryMac (Sep 12, 2018)

Nealtw said:


> Yup, is there a better word? It is still better than probable. I think like was suggested earlier, testing with a heavier weight would be my thinking.


*Better than probable*... based on what? Questionable thickness concrete of unknown compressive strength? Even the new concrete wasn't from a mix plant, if too much water was added who knows what the new concrete strength is?

*Testing*... it's a lift rated for 6,000 lbs. Most manufactures would test the 6,000 lift at 9,000 lbs to verify a 1.5 safety factor.

Would you lift 9,000 lbs to test your brand new 6,000 lb lift?


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## Nealtw (Jun 22, 2017)

HenryMac said:


> *Better than probable*... based on what? Questionable thickness concrete of unknown compressive strength? Even the new concrete wasn't from a mix plant, if too much water was added who knows what the new concrete strength is?
> 
> *Testing*... it's a lift rated for 6,000 lbs. Most manufactures would test the 6,000 lift at 9,000 lbs to verify a 1.5 safety factor.
> 
> Would you lift 9,000 lbs to test your brand new 6,000 lb lift?


I wouldn't test these things at the label capacity never mind a safety factor.


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## A Squared (Dec 19, 2005)

Nealtw said:


> I wouldn't test these things at the label capacity never mind a safety factor.
> https://www.youtube.com/watch?v=XLUjq6ijvVc



Wow. Silly me. I'd assumed that the basic mechanism would be capable of the claimed capacity.

I suppose that we can take comfort in the fact that it's unable to actually lift a load heavy enough to cause the failure.


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## Nealtw (Jun 22, 2017)

A Squared said:


> Wow. Silly me. I'd assumed that the basic mechanism would be capable of the claimed capacity.
> 
> I suppose that we can take comfort in the fact that it's unable to actually lift a load heavy enough to cause the failure.


I sent that to a freind who has a lift, he tells me now he lifts it a foot and walks around inspecting and then another foot until he gets it full height. I am sure he will get back to trusting it. :biggrin2:


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## HenryMac (Sep 12, 2018)

Nealtw said:


> I wouldn't test these things at the label capacity never mind a safety factor.
> https://www.youtube.com/watch?v=XLUjq6ijvVc


Buy an ALI certified lift and you'll know that at least it has passed the "Trust But Verify" rule.

Buy a non-certified lift and you'll know that at least it has passed the "Dude... Hold My Beer I got this" rule.

https://www.autolift.org/ali-directory-of-certified-lifts/


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