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Mtowner 11-02-2010 01:18 PM

Side walk replacement
The side walk pad has sunk where Istep up to the cement pad for the front stoop. It is a rather new home and I've been told by neighbors that the area has been filled in to make grade when the hous was built. It is only one pad of the 50' side walk and I would like to remove the one pad, fill to level, and repour.
My 2 part Question:
How do you mix the cement (what is the receipe) and How do you finish concrete. It is a sidewalk pad , 3'X6', 4" thick..
Any help is welcome

DrHicks 11-02-2010 04:23 PM

I'll assume you've never done any concrete work before...

That said, the BEST thing you could do is find out if you have a friend, neighbor and/or relative who you could pay to help you. This isn't a difficult job, but must be done correctly or the end result will be worse than when you started. So...

To remove the sunken slab, you'll need to pry up a corner (with a long heavy bar & wood blocks) and break it apart with a sledge hammer. Get if off the ground or you won't be able to break it.

Build forms, using 2x4s with "form stakes." Match one end of the forms to the pre-existing sidewalk. Make sure they're level from the stoop to the old sidewalk, but have one side slightly lower than the other (a perfectly flat & level sidewalk doesn't drain water). If it were my project, I'd put an "expansion joint" on the stoop end of the new sidewalk slab.

Pour some heavy-grade gravel into where you'll pour your pad. Level it out and tamp it down good. Without this base, your new pad will sink just like the old one.

For mixing the concrete, I'd suggest renting a small portable mixer like this. It will cost a little ($50 maybe), but will be worth it. Each bag will have instructions regarding how to calculate the amount needed. Pick up and extra bag or two. You can always take them back, but you do not want to run out in the middle of the job.

Mix 1-2 bags at a time. Use your garden hose and spray in water while the mixer is running. It is hard to describe the right consistency of the concrete, without calling it a "slump test," but roughly speaking, it should be about the consistency of pudding (maybe a bit stiffer). Smooth each "dump" of concrete with a small shovel until you have all the concrete you need in the forms.

Run a "screed board" (probably a 4' 2x4) across the forms to do the first leveling of the concrete. Fill in any low spots & re-screed.

If you don't have any kind of float, and don't want to buy one, you can use a short 2x4 (maybe about 1' in length) for the next smoothing.

After the concrete has set for a few minutes, use a hand trowel to finish the smoothing process. There is no magic to this, other than keeping the front edge of the trowel a bit higher than the back edge (not doing this will make you dig into the concrete).

For the best finished look, you'll want to "edge" your concrete as well.

It's kind of hard to describe, but not terribly difficult to do - assuming you take your time and carefully do things right.

AlwaysOneMoreProject 11-02-2010 05:27 PM

Broom after trowelling?

Mtowner 11-03-2010 07:03 AM

Should I broom the concrete after trowelling or just let it "as is" after trawelling. I really am new at this cement work and just want it to look OK

AlwaysOneMoreProject 11-03-2010 08:28 AM

I wouldn't trowel it. I'd screed, float, broom and then edge. Trowelling gives concrete that really smooth finish that's like ice when wet.

Also, I'm guessing that your walkway is light in color. You don't want to use bagged concrete for your project because it'll look awful because the bagged stuff is very dark.

I'd just order ready-mix. It may not match perfectly but it'll look professional and the cost of bagged white cement is so high, you may only pay a very small net amount for delivery.

I'd also build a little 2x4 form and a few bags of concrete and practice a few times to get my timing right. First time around, you'll probably over work it and you don't want to do that on the side walk.

DrHicks 11-03-2010 09:39 AM

^^ Good points. The only thing I'd disagree with - and this is just an opinion as to whether it's worth it - is ordering ReadyMix. He's needing less than 1 yard of concrete, and the ReadyMix company will almost certainly tack a "small load" fee on. It'd be nice, and convenient, but he may pay $150 or more for less than a yard of ReadyMix.

On the other hand, it might be worth it to him.

Redbirdseven 11-03-2010 02:49 PM

someone spoke above about ordering ready mix. You will not be able to order such a small amount as you will be needing for your project. Go ahead and mix up a sample from your bag mix and spread it out and let it dry to see what the color will be. If it is to dark then get some color to add to your mix to lighten it up. Try another test to see if you are close enough to match what you have in the side walk. Doing this is not hard and you will be able to match almost any thing in the future also.

AlwaysOneMoreProject 11-03-2010 03:34 PM

6 cubic' means he'll need two bags of white cement, iirc. That's $30. Then, he'll need some gravel, sand and a mixer. I'm thinking talk to neighbors who might want to share the cost of ready mix. :D

Can you dye concrete white?

astin 11-03-2010 04:30 PM

The concrete bag has instructions on it. Just follow the directions and it will be very easy.

DrHicks 11-04-2010 06:50 PM


Originally Posted by AlwaysOneMoreProject (Post 50719)
6 cubic' means he'll need two bags of white cement, iirc. That's $30. Then, he'll need some gravel, sand and a mixer. I'm thinking talk to neighbors who might want to share the cost of ready mix. :D

Can you dye concrete white?

Actually, you can get the pre-mixed stuff that only needs water added to it.

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