j_seph
Senior Member
Have played with the idea of doing this to make mine beter. Is there any real reason to go 4 inches thick? Would 2 inches thick be good enough. Looking to do on a budget (a Low one)
Woodsman brought up a good point. When you're done kenneling, a 4" slab can be re-purposed.
And I'm no concrete expert, but a 2" slab just doesn't seem thick enough to last. A few seasons of freeze/thaw cycles, and that slab will be spider webbed with cracks and crumbling away.
goal being squares. Any rectangle will crack
Any hydrated material will shrink once the water evaporates. You have probably seen a dried pond bed where the top layer cracked. It can withstand it when everything is equal. But say, a sidewalk, it being rectangular, it has to two forces, two masses pulling in a tug of war with not enough material to hold it. People call it an expansion joint. It's really a shrink fault line. Later, months later, it becomes a fault line to help with shifting forces but the shrink issue is over. I cut my fault lines as soon as I can get on it and not have cutting issues. If you cut 24 hrs later, you will probably already have cracks. If you cut to early, the blade will cut the concrete good however the aggrigate, the rock, will not cut but will pull up, giving you a nasty looking joint that can't be fixed. I can't recall the proper depth of the cut. That's a debate. Some even say 1/4. I go 3/4 on a 4 inch slab, slightly more on the edges, the last couple inches. If you start to pay attention to concrete that you see around town, you will notice a very predictable pattern in where it cracks. Always midway on rectangles. Always where a big mass joins another mass like where a sidewalk joins a slab, etc. Those crack control lines being symetrical and straight look so much better than a nasty random crack, LOL, however I had a homeowner once who was mad because he was not having those cut lines on his concrete. They actually went as far as to have another concrete guy come out and he told them it was done right and explained it to him.Did not know this. Can you explain why or ? Thanks
Any hydrated material will shrink once the water evaporates. You have probably seen a dried pond bed where the top layer cracked. It can withstand it when everything is equal. But say, a sidewalk, it being rectangular, it has to two forces, two masses pulling in a tug of war with not enough material to hold it. People call it an expansion joint. It's really a shrink fault line. Later, months later, it becomes a fault line to help with shifting forces but the shrink issue is over. I cut my fault lines as soon as I can get on it and not have cutting issues. If you cut 24 hrs later, you will probably already have cracks. If you cut to early, the blade will cut the concrete good however the aggrigate, the rock, will not cut but will pull up, giving you a nasty looking joint that can't be fixed. I can't recall the proper depth of the cut. That's a debate. Some even say 1/4. I go 3/4 on a 4 inch slab, slightly more on the edges, the last couple inches. If you start to pay attention to concrete that you see around town, you will notice a very predictable pattern in where it cracks. Always midway on rectangles. Always where a big mass joins another mass like where a sidewalk joins a slab, etc. Those crack control lines being symetrical and straight look so much better than a nasty random crack, LOL, however I had a homeowner once who was mad because he was not having those cut lines on his concrete. They actually went as far as to have another concrete guy come out and he told them it was done right and explained it to him.
Any hydrated material will shrink once the water evaporates. You have probably seen a dried pond bed where the top layer cracked. It can withstand it when everything is equal. But say, a sidewalk, it being rectangular, it has to two forces, two masses pulling in a tug of war with not enough material to hold it. People call it an expansion joint. It's really a shrink fault line. Later, months later, it becomes a fault line to help with shifting forces but the shrink issue is over. I cut my fault lines as soon as I can get on it and not have cutting issues. If you cut 24 hrs later, you will probably already have cracks. If you cut to early, the blade will cut the concrete good however the aggrigate, the rock, will not cut but will pull up, giving you a nasty looking joint that can't be fixed. I can't recall the proper depth of the cut. That's a debate. Some even say 1/4. I go 3/4 on a 4 inch slab, slightly more on the edges, the last couple inches. If you start to pay attention to concrete that you see around town, you will notice a very predictable pattern in where it cracks. Always midway on rectangles. Always where a big mass joins another mass like where a sidewalk joins a slab, etc. Those crack control lines being symetrical and straight look so much better than a nasty random crack, LOL, however I had a homeowner once who was mad because he was not having those cut lines on his concrete. They actually went as far as to have another concrete guy come out and he told them it was done right and explained it to him.
Yes, I could see that happening on a long sidewalk. On a typical pour, it moves ever so slightly. That's why expasion board should always be used in a confined area of concrete. Many front porches with a brick rolllock have expanded and barely show a crack in the mortar joint of the brick exterior rowlock, all the way aroundTo a point. Concrete also expands in extreme heat. Our sidewalks in our subdivision were given the standard trowel joints when they were put in 12 years ago (useless btw) and there is one section that we have had saw cuts done on because in the summers that are really hot it actually expands causing the sidewalk to lift a good 3" off of the ground at one of the trowel joints. (no trees, roots etc causing it) and once we did a series of saw cuts, problem solved.