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Discussion Starter #1
re: mudjacking. is it possible with some cracks?

I wanted to know, just by a quick look at these pictures if it is possible pursue mudjackers. The concrete pad is about 20x20 feet. control joints are about 4 to 5 feet apart. some of them have cracked some have not.

Obviously I will have to replace one 4x5 square that has been cracked all over. The biggest concern whether this will work or not, is i have two criss crossing diagonal cracks down the middle of the pad. those cracks are level to each other and have not really seperated.

Do you think it is possible to mudjack this slab? while replacing that one awful square?

 

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Looks like 1/3 of your sections are cracked through. Likely need to redo foundation beneath those slabs or repour those. Why do you want to mudjack?
 

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Discussion Starter #3
Why do you want to mudjack?
I want to mudjack because there is a negative slope against the house. maybe -2 degrees. whenever it rains, all of the water rushes against the wall. This patio has been there for 50 years (so i'm told). I don't want to redo it, because alot of other work needs to be done on the property's exterior, straining the budget. I don't want to re pour because it would be way too expensive.

If it is possible to mudjack, I would.
 

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id get a price on mudjacking and compare it to replacement. the replacement would be higher no doubt but you would have a new patio also instead of shelling a lot of money and still having the old patio.
 

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Mudjacking?

It appears your slab has dropped about 4 inches at the building (11 inch step at the door). That movement likely contributed to the cracking. The small sidewalk has dropped also creating a trip point. The majority of the cracking is at the outside corner, which is moving in two different directions. Slope is hard to determine, but a good rule of thumb is 1/4 inch per foot of outfall. Three choices exist to return to safe condition -lift, replace, or both. you should lift first if you do both. Lifting is cheaper and faster. Replacement costs more, but you can re-engineer and you get a new surface. To lift you can use sandjacking, mudjacking or foamjacking, depending on what services are available in your area.
 

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Discussion Starter #7
To lift you can use sandjacking, mudjacking or foamjacking, depending on what services are available in your area.
I am not familiar with sandjacking. I do live in a dense metropolitan area. Would mudjackers do that service as well? I wonder what the weight comparison to the other two is. mudjacking seems as thought it will settle due to the extra weight, and I am not to fond if the idea of foam.

I measured the diagonal slope yesturday. from the back corner to the front. there is a 3/4" negative slope in 21 feet. 2% slope is the maximum I can achieve without the slab starting to be higher than the basement window.
 

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Jack hammer the whole slab and remove it. The base under it is improper and it's all cracked.
Ron
 

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Most of the settling has occurred, given the age of the slab. Therefore, the slab should stay at design elevation if you lift and fill the void. Two problems with mudjacking are the product has moisture and is a single step process. The excess moisture will evaporate and the filling to get lift, must stop filling, when it's high enough. Sandjacking doesn't have those limits because it's a two step process. Normally, the foam is too expensive and has other issues as well. Since you probably only have access to mudjacking, your best bet is to drill holes on a three foot grid to ensure filling as best as you can, and slightly over lift to compensate for future settling. Your slab has a lot of service life left and removal can only stir up the ground starting the settling process all over. Not to mention, replacement is the most expensive method. Good Luck!
 

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Cons; Like mudjacking, foam can crack the concrete. I mentioned it's the most expensive, it generally costs $432/cu yd for the product not counting profit for the contractor. It's a chemical reaction which goes until completion - translated - it's possible to over lift. It's exothermic, dependent on temperature, cold limits the expansion. Like any viscous product, after leaving the gun, the foam decides where it will lift. Like mudjacking it's possible to lift and not fill. Single step process. Not biodegradable. Some components are toxic. Pros; small 5/8" holes, 1-2 man crews, quick, no disruption.
 

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If you jack a cracked slab, won't the cracks still exist to draw water for winter heave/separation? I would think you have a high point putting pressure there to make diagonal cracks rather than follow the relief control joints..... I second Ron's vote to remove, re-grade, and replace.

Gary
 

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Discussion Starter #13 (Edited)
I would like to remove regrade, and do a proper job, but I got scared away from a high quote. I would really like to put interlocking, but the cost is too out of reach (i think), and if I am spending all this money, I wouldn't want to put concrete back in the same place. A local contractor wanted approx 10k just for that job. it seems too steep for 400 sq feet +150sq feet for a walkway for a new concrete solution, also there is some regrading in various areas around the house in that quote. For Interlock, maybe that's reasonable, but it seems a steep cost for concrete for that job size. correct me if i'm wrong

I am not sure how much the mudjacking would cost, i figured somewhere around 2-3k. for the cementicious type. and that's about 4 inches of lift along the walls of the house

Unless there is a an option besides mudjacking (risky), new interlock, or new concrete, I am fresh out of ideas.
The concrete has been there for 50 years (so I'm told), I am wondering how much more can it possibly settle even with the extra weight if I mudjack. That's 50 years of undisturbed earth.

the cost thing is also big issue becuase the driveway has to be done at the same time, also a grading issue.
 

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Gramps416, A couple of times you mentioned the slab settling (I am wondering how much more can it possibly settle even with the extra weight if I mudjack). Can you explain what you mean by that?

The settling around a building is an ongoing process that can take many years to achieve. Where the soils consist of fatty or expansive clays, that time frame can be 60-90 years to settle at 23% of volume. Sandy soils settle much faster at a lower ratio of volume.

Water accelerates the settling. You see the greatest movement at the downspouts. This settling is happening all around the foundation... under the driveway, the front steps, the patio, sidewalks next to the building and especially the trench for the sewer and water lines serving the house. Normally, for the flower garden, we just throw in a little extra dirt to replace what disappears. However, nobody replaces the soil under concrete because of "out of sight out of mind".

This happens because of the way we build. The stages of construction mean different crews come and go and the continuity of craftsmanship gets broken. For instance, the concrete crew shows up after the soil is replaced around the foundation and they have no idea where holes where dug and settling will happen. The true fact of the matter is there are more holes under concrete than anyone knows about.

Your slab has settled, but doesn't mean it's touching the ground in all places. It's an almost certainty there is an underground reservoir next to the building and wherever someone dug a trench. When it rains, because these reservoirs are lower than everything in the vicinity, they fill with water. Over time the saturated soils will slough off (erode) to cavities way deep down and the process continues unabated.

All of this is magnified by where you live. If you live at elevation or above the thirtieth parallel, you can add in the worry of frost. Water freezes and expands and we bury our pipes deeper the further north you go. I don't know where you live, but the extra cracking at your sidewalk corner looks like frost cracking. The water under concrete contributes to it's demise.

With that said, I'll get to my point. Your choices are simple... I think. If the surface and overall condition of your slab is good, don't replace it , repair it. How it's repaired makes a big difference in how much damage is done to the slab and how long it lasts. The best, least intrusive, and longest lasting repair is sandjacking (costs vary widely from area to area, but usually under $3/sq ft). If not available, you should mudjack, which should be cheaper. Look for a mudjacker who drills small holes (1.5-1.75"). Use an electric hammer drill (less destructive) instead of air rock drill to drill holes in a grid no more than three feet apart. Stagger the grid. Forget the cementitous aspect, it's only a placebo to make you feel better and costs more. If they have crushed Limestone or lime sludge from water treatment plants, that will suffice. Keep the moisture level of the material at 40-50%. Too stiff doesn't fill, too wet will shrink from water loss. At 50% moisture you will lose 25% volume to water loss.

The biggest problem with mudjacking is most contractors buy into the industry boast of "when the void is full, the concrete lifts". Not true. The void is never full and most contractors come to know that if you pump in a stiff mix it lifts right away and the job goes quicker. Not all contractors are alike. Some can resist the urge to cheapen the work done to make more profit and some can't. Plus, nobody knows how common or how big the voids are because the voids aren't filled reliably.

As for longevity, a proper repair should last you 5-10 yrs or more and it won't drop 4" because if you fill it, that product will not disappear.
 

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No amount of jacking is going to fix that mess in the first picture. Remove and replace is the only option I see for that section.
 

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I don't think that slab its worth spending money on mudjacking.
What happens if mudjacking doesn't work? You have to spend more money to do what should be done at the first place.

If the budget its tight have them do only half of what you have right now..
10 x20 along the house to keep the water away.

10k would be a high price here in Chicago to have that slab replaced.
Last time i checked was around $7-8 a SF + removal ...
Maybe you can rent a jack hammer and DIY to save on demo...
 

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Ive used mudjackers before and while in the short term it did raise the areas, within a couple of years it began to drop all over again. Plus the additional pressure to raise it all will likely create even more cracks then what currently shows. We had no cracks before we used mudjacking and a few cracks afterwards, plus those ugly circular holes where they do the jacking.

My advice is remove it all, fix the base and heavily tamp properly and pour the new. If you can't afford it all, then do at least the sections next to the house now and save for the rest at a later date.
 

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Discussion Starter #19 (Edited)
If you jack a cracked slab, won't the cracks still exist to draw water for winter heave/separation?
I think there is a distinct possibility this can happen. But what are the chances? I wasn't thinking this solution of being long term. more like a 5 year thing.

Gramps416, A couple of times you mentioned the slab settling (I am wondering how much more can it possibly settle even with the extra weight if I mudjack). Can you explain what you mean by that?
The slab has been there for 50 years. I was wondering, if during that time, the soil around the house has settled from the original construction date, since it has not been disturbed. Where I live, our soils have a very high clay ratio, to the point, whenever someone wants to dig holes here, (the smart ones) don't even rent an auger, we call a company who specializes due to the difficulty to move that soil. I guess it can still settle, you mentioned 60-90years for clay soils.

This settling is happening all around the foundation...
Your slab has settled, but doesn't mean it's touching the ground in all places. It's an almost certainty there is an underground reservoir next to the building and wherever someone dug a trench. When it rains, because these reservoirs are lower than everything in the vicinity, they fill with water. Over time the saturated soils will slough off (erode) to cavities way deep down and the process continues unabated.
this sounds very much like what is happening here.
I was wondering, if cavities exist under the slab with possible resoivoirs, the mudjacking would not fill those voids?, being submerged in those reservoirs. I wonder why they don't pump the water out if required, (since they are drilling holes anyway in a grid pattern)

Your argument for sandjacking is logical and convincing, I don't know if anyone in my area does it. I was wondering if mudjackers, sandjack as well. I wonder if it goes by any names

No amount of jacking is going to fix that mess in the first picture. Remove and replace is the only option I see for that section.
The truth is, this is a stop-gap solution. I would like a nice patio, instead of an 50 year old ugly slab, but the yearly house maintenance budget is too large this year to get what I really want.
 

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Spending 2-3 k for a stop gap measure makes no sense to me, but it's your house.
 
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