Cracked concrete walkway

I would close your blinds or shades on that window so you can't look outside.Best would be cut our a 3 foot section and re pour it also put wire and re-rod in the new pour so it will not crack.

have a nic summer.

Pour epoxy and over coat with floor paint to have a uniform look.

I like the idea of using bricks and am thinking that I might also use matching bricks to border the walkway to tie things together. I just uploaded a video to youtube showing the walkway (including "closing the drapes option" :)) http://www.youtube.com/watch?v=1JSeq9keZ0w

I do not think that a monolith walkway as long as 30 feet is a good idea. Concrete shrinks and expands at different temperatures and this is why they have expansion joints and make a walkway in small sections, leaving a small gap between adjecant sections.

vshwn7@aol.com

....with some sort of "gasket" or seal to prevent water and debris getting in it.....

but I would wait a year or two.

Ah, yes, GOOD ANSWER an excellent strategy...I try it on all those jobs Mrs Cat finds around the house.
Del

What's a year or two? Is he moving? Is his house on some show?

If it saves him from having to saw cut out addition patches when cracking accures later I would say wait. I would let it settle then fix the problem.

Just so you know, Mrs Baker would not care for any of the ideas posted she would prefer it done right the first time, but if repairs need to be done she would prefer it done right. If that means having hair line cracks for a year so be it.

Waiting for a year will be the easy part as pretty well tied up with other projects. I haven't entirely settled on the "brick" option however - still open to other ideas. The walkway on the other side of the landing (I believe the landing is visible in the Youtube video) did not crack over the winter. Any correction technique that I use on the cracked side will, of course, have to match the other side of the walkway. http://www.youtube.com/watch?v=1JSeq9keZ0w

Is it possible for you to divide you walk by (8) 5 ft sections? That way you could then remove the sections where the cracks are and repour those areas. I was train old school so I use alot of felt which can be placed where the new pour will meet the old pour so it will be able to flex easier.

While you have it rip up you can check on the sub-base for settling also.

After pouring brush then cover with old burlap bags or straw and keep it wet. The longer its wet the less likely it will crack and the stronger it will become.

On the other hand, if you make the cuts now, both in the cracked walkway and in the as-yet un-cracked one, it will prevent (or at least greatly reduce the probability of) additional cracks from appearing in undesired locations.

I do have to admit that I thought of the brick solution 39 years ago, when I moved into my current house, which had a similarly cracked front walkway of similar construction and dimensions. I really should have done it on one of the two occasions when I had to pass a pipe under that walk. One of these days I'll get around to actually doing it...

Speaking of pipes, I forgot to mention that I did think of pipes when I did the walkway. Specifically I was worried about the cold water supply pipe that runs under the walkway. I Embedded a heavy duty power line guy anchor, that I happened to have on hand, in the concrete. Just removed some sod to get a shot of the guy anchor end (see photo). The idea is (if I had water pipe problems) to cut the concrete on either side of the guy anchor and hook on to the guy anchor to pull/lift the section out. Not sure if it would work but figured no harm in trying.

Well done! Of course it would work, assuming the adjacent cuts were deep enough.

Unfortunately, my walk was already in and cracked when I bought the property. I just took a look, and I can't tell if the cracks are any different than they were when I got here almost 40 years ago. The house was 8 years old when I bought it, and so presumably the walk had already been cracked for 6 to 8 years.

Dick

Whatever you decide to do (I personally liked the brick idea), remember that the cracks will "work" over the next few years, so do not do something that is "sticking" both sides together as it will only crack again......do something that can "flex" a bit.....that is why a nice line of bricks, mortared together is a good choice......or make a big cut and fill with silicone/rubber or similar.

You can also buy rubber "gaskets" for between concrete blocks, how thick they can be I have no idea......

Make a "design feature" of the problem if you can......

As you might suspect, I did not make any strain relief cuts

Experience can be a cruel mistress. I guess wise-cracks won't make you feel any better.

Lay carpet ? Crack the windows to match ?

Sounds like you're ******d.

Is there any kind of surfacing you can out on top of the concrete ? If you fill the hair-line crack it might well end up being more obvious than before. If you were someplace dank like England, you could make more cracks, then let some nice green mould spread over it. Honest, it can look quite OK (as long as grip is not a problem). If the cracks are straight enough, maybe you could use some kind of router to make a pattern that looked intentional. Just how big is "hairline" ?

HI,

I have seen such cracks on RCC roads being filled up with bitumen. These cracks are developed due to expansion in summer and contraction in winter.

Suresh Sharma.

I guess you learned a lesson.

The problem is that if you do nothing you could end up with another problem in winter. If water seeps into the cracks then freezes it will obviously expend. This could either lift the concrete or cause more damage to the slab.

I do like the brick idea also. But if you go with that I would suggest that you put in expansion joints at 5 or 6 foot intervals.

If you try to fill the cracks with any material you will just make them more noticeable, unless you use an industrial paint over the entire slab. Then you will need to repaint the slab regularly.

Your final option is to rip the whole thing out and start over from the beginning, with a few changes to correct what was left out the first time. Or hire a contractor if you can afford it.

Good luck!

Poured concrete is never greater in volume and dimension than at the time that it is placed. If too much water has been added during placement, the shrinkage during curing will be greater than if it was placed at a low slump. Ideally, slabs should be saw-cut within four hours of finishing, as the internal stresses that cause cracking start to build as soon as the hydration process starts. A good rule-of-thumb is to make relief joints no more than 15' apart. If you have a narrow section such as a walk, you could make the interval 5' or 6'. The inclusion of reinforcing mesh will not prevent cracking but it will help prevent differential vertical movement at joints or cracks.

Expansion joints only serve as isolation from walls and other more massive elements to allow slabs-on-grade to move up or down as soil conditions change on acount of frost or moisture. They can be an advantage where dirt and debris could fill the shrinkage joints during lower temperatures to the point that later expansion during higher temperatures causes spalling at the joints, however they don't need to be placed nearly as often as shrinkage joints. Often, resilient joint fillers are specified to prevent this from happening.

Like the guru said, Experience can be a cruel mistress. I have poured a lot of flat work and you will always have hairline cracks in large pours. Indoors they don't usually amount to much but outside over time with freeze thaw cycles they will get bigger. You can use concrete crack fillers but I have never seen this work very well. You have two options. Tear out and start over or I like the epoxy coating solution above. It would be cheaper and you could use many different colors. I think it would look very nice. One thing about concrete, It has a very long memory of how well it was formed and poured.

Check out methods and products on ConcreteNetwork.

Because the walkway has been there a while now, you'll have to prep it good. Doing that will probably take more time than actually applying a finish. You should be able to find some kind of ready to use gunk, that you can trowel/brush/whatever over the entire length of the walkway - depends what kind of finish you want. The site I linked seems to have leads to a wide range of products/methods.

It would be great if you can get back later with some before and after pictures. Hearing first hand which method works may well be useful to us all at some point.

If you pour again, use plenty of rebar in the mix........

....and use 6" lengths, else it'll get stuck in the mixer.

That was meant as a joke surely?

...oops, I should have used metric......

With a concrete walkway or a slab on grade the key is to never exceed 10 lineal feet in either direction with out a tooled joint or a saw cut, reinforced or not.

Dow Corning makes a product called 888 silicone which is gray in color, there are 2 types a knife grade which is for a vertical application and a flowing type which is for sealing a horizontal joint or in your case a crack, no silicone, epoxy filler or topping will make it look new again, they will mirror and the crack will appear again.

Your best bet will be to saw cut and remove the effected areas and replace it, it would also be a good idea to install 1/2: expansion joint material. also be sure and have your concrete contractor saw cut any areas that are longer than 10 lineal feet.

Good Luck!

Mark

yupe2be@hotmail.com

Much good info. here. I would stay away from epoxy, though I love the stuff for bonding, its resistance to sunlight is poor. The best sealer for the expansion joints is a two part polysulfide. It is stickier than silicone, and way more resilient. Gently caulk the joints with soft nylon rope to within an inch of the surface. For a professional looking job put 2" masking tape on either side of the joint, fill carefully and use a gloved finger or tool to smooth the joint immediately. Remove the tape as soon as the caulk begins to skin over. To accelerate the cure, spray occasionally with a mist of water. For smaller jobs use Boat Life polysulfide in your color choice.

So you mean to make the cracks behavior as expansion joint...I did use polysulfide or (Thiocol) too many times, but for non movable outdoor cracks i used used epoxy injection first, after epoxy curing time, i did open the crack 0.5X0.5 in. sq., then filled with Polysulfide, by the way, What about one component polysulfide?

One part polysulfide is available at marine supplys as BoatLife^® caulk. Thiocol as I know it is clear, has wonderful properties, etc. But it is important to fill the bottom of the cracks with fibrous material (cotton, hemp, jute, rope) for any caulk/filler you choose. This is so that expansion and contraction can occur without the additional stresses of contact with the bottom of the joint, where an additional dynamic (2nd plane) will pull the caulk from the edges of the joint.

A dusting of RediMix or stone dust to the uncured filler will help hide the repairs.

Best of luck

Carl

I didn't think cutting gaps in the concrete would do anything other than giving the cracks a head start. My driveway was poured using fibre-concrete that is supposed to help keep the concrete from separating when those enevitable stress cracks appear. Mine now has cracks and part of it I reckon is due to the fact that the guy didn't tamp the earth beneath the pour. But in my new detached garage, the earth was compacted using a power compactor, fibre-concrete used, and grooves cut, but I still have cracks. How about a nice rug over the whole damn thing and outdoor carpet for the driveway?

Maybe your house is built above old mining tunnels or a Volcano wants to "out"?

Seriously, when tamping, it needs to be redone as each 2 or 3 inches of soil are replaced, not just once when the hole is full.....many do not understand that.

Its really a 2 man job, one drives the vibrator back and forth continuously, the other shovels the earth back into the hole continuously.....easy when you know how......

O.P. here - I did a pretty good job of tamping as far as I know. That brings up another question that I have re this section of the walkway (there's another section of walkway on the other side of the landing and it came through the winter just fine); if we assume that the tamping job was "good" and evenly done along the full length of the walkway, what would you expect, in terms of cracks, if a heavy load was placed on one end of the walkway? I'm asking this because during the winter I noticed what appeared to be tire marks made by a very large tire. I mean much larger than from a pickup truck for example. Perhaps a large dump truck. One wheel of the vehicle did land on the extreme end of the walkway (as indicated by the marks in the snow). At the time the walkway was mostly covered by snow and ice. One crack is 7 feet from the end and the other is about 18 feet from the end. The overall length is about 30 feet. Does this pattern of cracks possibly mean anything re the heavy load?

That would do it!. Especially if there were already stresses due to freezing of different moisture contents under different sections of the slab.

If there are any areas not well tamped, it doesn't take much. I once cracked an 8 year old patio slab by driving a "Bobcat" across it. Turned out most of it was essentially on bedrock, but one end was on fill that had settled.

Maybe it's like spaghetti.

Thanks Kris... good info re possibility of experimental analysis of what went wrong with the walkway.

A heavy load could be a factor depending on the thickness of the concrete and type of concrete used. Then compound it by any problem with the sub-base and the fact that its a straight pour with out any any flex joints, could possible be your culprit. Its hard to say with out being there to see it while the work was being done and see it now.

Bit late getting back to you because of posting problems. The concrete I used was 30MPA 20MM which is the same stuff used for sidewalks here. I took a gamble not cutting the walkway but because I didn't anticipate any heavy loads I figured it might work out. However the cracks could well have been due to frost/thaw. The concrete is about 3-4 inches thick. Tamping was thorough as I made sure I got full value for the rental time. Here's a couple of pictures taken during the job.

Too thin.....8-10" with rebar.....if I had done it.....

When it comes to home concrete projects I usually over kill it also and bring it to industrial grade.

The patio I poured which was a year and a half ago was a monolithic pour of 30' x 20' with ~8" thick on top of 12" wide by 3' deep footers with 4000 psi concrete we call it AAA. In the middle of the footers I put 10" of 1 1/2" stone compacted by a jumping jack for over an hour. the pad itself had rebar spaced every 12" tied to the top of rockers. It was done in the middle of summer so I sprayed it every 3 hours with water (timer and sprinkling system)with straw on top. As of right now no cracks I also haven't put any loads on it yet that will come with the roof, and when we have our annual family picnics.

I'm not familiar with 30MPA 20mm concrete here I would use a class AA concrete which is over ~3500 psi strength. The side walk pours I did usually had spacers ever 8 feet or so with felt between them. I'm sure there is something better out there now then felt. The thickness we usually did was usually at least 6" for non-load baring sidewalks and 8" for load baring (i.e front of a driveway) with at least 10" of crushed 1 1/2 inch stone compacted underneath. I usually use what's called a jumping jack, they usually do a pretty good job of compaction.

In PA we have the second to the most in Freeze Thaw cycles in the US some where between 75-90 days a year. So I know what its like to deal with that problem. I've seen whole sections of sidewalks end up looking like a roller coaster in Philly after one bad winter because of all the freeze thaw cycles.

Like me, another one with Germanic liking for a job well done, and only ONCE!!!

Congrats from me......you did well........

Florida being hot most of the time, how long did you keep it wet? If the cement drys to quickly stress cracks will occur. It could be dirty stone, bad sub-base, a hot load (a load that has been in the truck to long), etc. the lisit could go on cement is pretty fickle some times.

My garage floor was done in the dead of winter in PA. The builder instead of using warming blankets which would have keep the surface moist but allowed it to cure Decided to use salamanders to heat the concrete which dried it out he also never put saw cuts across it. So several stress cracks developed across my four car garage over a period of two years. After the garage settled I opened up the cracks caulked them and painted the garage with epoxy garage paint. If you look hard enough you can see where the cracks where, but other then that it's sealed and protected.

The garage floor was wetted and covered with plastic sheeting. For the drive, just tried to shower it with a garden hose whenever I thought about it for a couple days.

When I was very young we lived in Germany where my dad worked for the Corps of Engineers as a civilian. he was impressed by all the pre-stressed cement they installed. Light poles, sidewalks, etc. Strong, relatively light, and very durable.

To bad we don't take that approach here. I am sure it has to do with the economics of the situation. (Don't want to pay more than a minimum, so we get what we pay for. Rather than paying up front for the 'do it right the first time' approach.)

All I have seen here is pre-stressed on pre-engineered items, and post stressed on things like house slab foundations (soil was gumbo clay over an old rice pattie prior to sub-division development) along the Gulf Coast).

It doesn't help when trying to fix already installed concrete.

you should have used fabric reinforcement , at least for the top with 30cm from the top level!

doing it continuous be better!

hi all, an easy "fix", put a diamond wheel on your 4" angle grinder and grind out a 1/4" groove in the crack and use some concrete caulk to fill in the groove, then saw cut some control joints every 5' so it don't happen again. the concrete caulk stays flexible thru hot and cold and prevents moister from getting in the crack. we use stuff like that up here north of the 45th parralell and it works well. if your slab is only a year old, this would likely be the most economical way to make sure it will hold up for the next 20 years. the caulk will eventually blend in with your slabs color, and some of the caulks are stainable so you could get some concrete stain as a final touch to make it look really nice without spending another $300 or so on new concrete. just remember, concrete is stupid, it has no idea what you put in it, on it, or do to it, it has already done the 2 things it supposed to do, get hard and crack. good luck, whatever you do!

Brings up a point that I am wondering about - in woodworking we sometimes collect sawdust from the project wood and combine this with glue to fill-in and minimize the visibility of a crack/hole. Is there any similar idea used to cover up cracks in concrete that anyone has tried?

IMHO : .. the craftsman 's eye always spots his flaws ....

waiting a year or 2 won't make that any easier..sometimes the concrete cracks due to the drying process... " interlocking paver's " ..beautiful when matched to the walkway from the house's front steps...i live in Calif. ( yes San Andreas is my neighbor ) i used sand 20 grit .. about 12$ a 100lb bag.. i expect movement..digging up the mortar repeatedly just didn't appeal to me...20 years in the same house ..over 600 bricks..havent had to repair the walkway once... weed it .. oh yes , repair it structurally. no

good luck

if all else dosent appeal to you :

maybe stop drill the cracks; ( not to much faith in cosmetic attempts to " hide " the cracks ) .

won't stop `em from bothering you but the stop drilling would stop the migration of the crack ...

If the crack has not covered the distance yes, but I understood (wrongly?) that the cracks are from one side to the other.....where would drilling then help?

Andy the two cracks go completely across the walkway. One is almost perpendicular but the other veers off from vertical about 20 degrees or so (just rough estimate without taking another look).

I was answering someone who want to drill to stop the cracks going further (into the lawn maybe!)

..i thought the the cracks were on the longitudinal axis....but my 1st choice was to replace the broken " cracked " work with pavers....if you read both statements...then you might have understood that the 2nd post .

I did not find it difficult to understand that the cracks ran from side to side....the confirmation was not needed really....but for you we will do anything to assist.....

If you have to do it all over..... http://cr4.globalspec.com/blogentry/8937/Bendable-Concrete

If you re-pour, try some polypropylene reinforcement fiber (fiber mesh) I poured a 12x24 slab with....no rebar!...OK it was a crazy gamble, but it was not really critical so I thought I'd experiment. The slab was 3.5-4 inches thick, hand placed and hand tamped (by myself I might add... you should see my fore-arms ). No stress relief joints, No cracks...not even one! The slab has been in place for about 4 years now.

Sometimes you get the bear other times the bear gets you.

Using concrete is a gamble sometimes everything falls into place other times just one factor is out of whack and you end up with cracks. Luck of the draw some times

This is true...there are many, many variables...