sidewalk

[Duane Smith]

Heres the situation got a sidewalk that needs replacing. Havent seen it all yet but from what I know it is 40ft long subject to snow/ice/freeze/thaw. I plan on probly replacing all of it. My thoughts on this would be to break up whats there and remove. Frame and pour. I was talking to someone else and his idea is to place forms above the exisiting concrete using the old sidewalk as a base. My thoughts on this is that it will still move and break up the new slab. Possibley even get water to freeze between the slabs.


Any thoughts on this?



Ps. Pouring a new slab was thinking about 4 inches of slab. Does that sound about right?

 

[Gary Swart]

Remove the old, soak and pack the soil, form up, and pour new. 4" is plenty for a sidewalk. Put expansion joints every 8-10 feet.

 

[Sponsor]

 

[hj]

The big question is where is the sidewalk? If it is along the front of the property then the city has to approve your installation, and it has to be done to their specifications.

 

[Bob NH]

Between those expansion joints, put a groove about 1/4" deep. The point is to let it crack there, straight across, so you don't get ragged cracks. You WILL get cracks in a 10 ft run of 4" thick sidewalk. They make a special tool for it, or you can make your own with some wood. Use a straight edge when you put in the grooves. If you look at a pro job you will usually see a narrow smooth section next to the groove. That is where the grooving tool left its mark.

You can use the same tool along the edges to round them off a bit. You don't want sharp corners when you strip the forms.

If you are making a right angle turn, or any sharp turn, put one of those grooves across each section, intersecting at the inside corner.

Take a look at sidewalks put in by pros if you need to get an idea what I'm talking about.

You should not finish a sidewalk very smooth. The usual process is to finish it, and then, while it's still fairly soft, pull a push-broom across it. Again, look at the finish on some pro jobs in a shopping center. The brooming is usually done BEFORE the grooving.

You will want to have a little bridge that you can crawl out on to do the grooving.

Your forms should be solid enough to stand up when you screed the concrete. Your screed should have a little arc in it so the water will drain off. It's nice to have a helper on the other end of the screed because you need to hold it down against the forms on both ends.

Then you will need a float, which is a board maybe 3 ft long with a handle that you will use so you can finish it from one side, after you screed it, without having to reach over it.

Don't float it too much or you will bring up too much water and fines that will leave pock marks when the water evaporates.

The best (strongest) concrete is mixed with as little water as necessary to be able to work it. Then, after it sets, you want to keep it moist. It shouldn't dry out for a week.

One problem with mixing your own for small jobs is that it is hard to get a good mix of aggregate. They seem to sell stone and sand, but nothing in between. If you can get it, it is best to have a range of sizes. The medium stone fills the spaces between the big stones, the sand fills the spaces between the small stones, and the cement fills the spaces between the grains of sand.