"WHEN DOES CONCRETE CRACK?"

 

Yes, concrete cracks. There, I said it.

 

The facts of life with hard surfaces:   Concrete cracks!   Pavers settle and get weeds!   Asphalt settles, cracks, and crumbles!   Decks
are expensive and wood decks need alot of maintenance!   Flagstones, bricks / mortar are also expensive, crack and can come loose!

 

This isn’t a sales pitch, just the grim reality of these surface choices. All surfaces have their “baggage”. You must understand that no surface is perfect.
Please take some time to understand the pros and cons of the surface you are considering and select one that you can “be ok with” the disadvantage and the downsides as well as the upside of that surface type.

 

Ok, so that said … for this article we are focusing on a concrete surface and discussing WHEN concrete cracks.
The short answer is that concrete can crack AT ANY TIME starting just hours after it is poured.
Have you ever heard someone say …      “Well I thought I’d get at least a few years out of the concrete before it started to crack …. “ This is a very common misconception. Concrete doesn’t necessarily crack because it is aging and decaying over time, it cracks for other reasons, but time isn’t really a reason, and it just doesn’t work that way.

 

If I only had a nickle for every time I heard a homeowner say … “Look at this concrete how it cracked .. I’m pretty sure its because the contractor didn’t do a good job … “ Hmmm, the contractor is ALWAYS the convenient target, but really … concrete cracks for lots of reasons. Yes, if your contractor does a “bad job”, it can promote cracking to some degree, but more often than not, concrete cracks because concrete cracks … Even the best poured concrete has a high probability of cracking.

Most concrete customers don’t want to hear the reality … concrete cracks, and it is a normal and undesirable “side effect” of concrete .... but read on, there is actually an upside to this dismal news ….

 

Smart and high paid engineers have been working on formulas for concrete for over a hundred years, and yes there have major advancements, new techniques, new chemicals, new additives, but the fact of life about concrete cracking, really hasn’t changed much over the years.
So back to the WHEN question … the contractor has control over certain aspects of the job, but assuming they did a reasonable job, concrete cracks when it wants to, there is just no particular time-frame associated with it ...
So here comes that better news ….

>>>   IF YOU CAN’T BEAT ‘EM ----- JOIN ‘EM

Ever heard this?  Well, many dozens of years ago concrete contractors and those that produce the concrete itself, for all practical purposes gave up on stopping concrete from cracking … not completely, but more interestingly, attention turned to controlling the location of the crack instead of trying to stop the crack from happening to begin with.

Is controlling the location of the crack just as good as stopping it from happening to begin with? Hmmmmm, interesting question. What if the concrete cracked, and we did such a good job at controlling the location of the crack that you never even knew the crack happened?
Wow, that’s pretty interesting!

So if concrete is concrete and cracks just happen, how can we control WHERE the cracks happen.  <getting a bit off topic with WHERE vs. WHEN … but really, read on …>

 

Here is a little experiment for you … get out a saltine cracker. Hold it with 2 hands and bend it up in the middle with your thumbs until it breaks … where did it break?  Yes, on the perforation!  Those little dotted holes in the middle of the cracker is a perforation line … why did the cracker break there?  Because they weakened the cracker by creating the perforation. It broke at the weakest spot. Kind of like when you cut a piece of tile or glass, you score it first, then you’ll get a clean break on that score line … you are weakening the tile or glass for the purpose of the break.

Concrete installation uses the same concept. Have you ever noticed those lines or grooves in a sidewalk every 3-4 feet? Most people think those are there for “expansion and contraction”. Another common misconception. Those grooves are called “Control Joints” and are actually there to act like those perforations in a saltine cracker.

They are there specifically to weaken the concrete, so in the event a crack is going to occur, it happens at the weakest point, along that control joint.
FASCINATING!

And the best news is, that this technique actually works! Next time you walk down a section of sidewalk, look down into each of those grooves. Typically down in every 4th or 6th or 10th groove you’ll see a hairline crack … never saw those cracks before did you! On a stamped concrete patio, we typically saw-cut these joints in 24-48 hours after the pour with approx 12-foot spacing, but function the same as the grooves on a sidewalk. Sometimes you will also see cracks at the base of a step, where the step meets the walkway, that is also a weak point and that hairline crack is typically neatly hidden in that crease.

Note: There is also a different kind of joint, a kind of spacer, called “expansion joint” which actually IS for expansion and contraction that is typically placed between your new concrete and other structures such as a house or porch.

We estimate the control joint technique to be approximately 95% effective. That is, less than 5% of the time, do we get calls from customers reporting random cracks that are outside of these control joints. We call this a success!

For you, the customer, those odds are very much in your favor that you will either never get a crack, or if you do, it will be “hidden” down into a control joint and you’ll never know it’s there! The downside is that if you are one of the 2 or 3 “unlucky” customers that gets a random hairline crack outside of a control joint, yes unlucky, no, not covered under warranty, but never grows to be wider than hairline due to the steel reinforcement placed into the concrete. Never have seen this develop into the unsightly “fault” or tripping hazard that customers fear. (We can discuss some minor treatment options at that time)

Well, that’s about it for now on the cracking topic. Hope this was educational and helpful for you.
Bottom line is this. Concrete cracks.  But with proper installation techniques including ground preparation, appropriate concrete mix, steel reinforcement placement, and proper control joint installation, it is highly likely, that you’ll never know the crack ever happened!

Enjoy your concrete!