Sidewalk crumbling...can it be repaired ?


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Old 11-06-05, 09:43 AM
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Sidewalk crumbling...can it be repaired ?

A poured concrete sidewalk of 17 years in age is now crumbling mainly at the expansion joints. One sidewalk edge is "exposed" to a driveway...and that edge is where most of the damage appears to be. Since this is located in a nasty climate with lots of snow, I can speculate that SALT had something to do with this problem.....possibly, the melted snow+salt crept into the expansion joints to weaken the cement over a period of years.

Short of jacking and repouring a whole new sidewalk, can it be repaired ?
The worst spots are the ones where there is a 4-6" v-notched "crater" right at the side of the driveway.....right at the top-facing edge.

I see several problems:
1) How do I get the expansion joint material into that irregular crater neatly ?
Looks like I must cut the pattern of the joint material to meet the shape of the crater.

2) How will the expansion joint material be held in place while the cement filling is applied to either side of it ?
Obviously, I'll be a piece of plywood along the edge near the driveway....held in place with some bricks or concrete blocks.

3) Which cement should I use ? (http://http://www.quikrete.com/catal...ete%20Mix.html) Looks great !! (I wonder if HD or Lowes stocks it though ?)
4) How do I get the patched areas to be matched in color ?

ANY ADVICE OR ASSISTANCE GREATLY APPRECIATED.
 
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Old 11-06-05, 10:03 AM
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Sidewalk crumbling...can it be repaired ?

You should consider a planned replacement of the walk.

The old concrete is 17 years old and who knows how good and uniform it is?

The areas with the most severe exposure conditions have failed. The rest is probably not far behind.

You are considering adding patches to the existing concrete. You will have a problem getting the new to bond to the old without removing all unsound concrete and using an latex additive. Still, it will just be a patch.

Fiber mesh concrete would be a waste of time for this. Mesh concrete is dependent upon proper mixing and you have not control over your uniformity and amount of mixing compared to a ready-mix plant that has controls and does it every day.

The color will not match. Your new concrete will change color during the first year.

Dick
 
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Old 11-06-05, 04:58 PM
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Thanks...but..

I am surprised 17 years is a long time for such a supposedly "durable" material !!! In afterthought, the walk has deteriorated not only due to harse winter conditions and salt application, but lack of a proper SEALER that should have been applied each fall.
Why is concrete color-matching such a tough job and what is the typical color progression with age (light-to-dark or vise-versa ?).
Actually, the non-attacked portion of the walk is in good shape.....making it so apparent that salt seepage in the joints was the major cause of damage.
 
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Old 11-06-05, 08:48 PM
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Sidewalk crumbling...can it be repaired ?

Concrete is durable if it made of good materials in proper proportions.

Often, concrete for sidewalks is mixed on site and not ordered from a ready-mix plant. Consequently, there is a wide range of quality and properties. Air entrained concrete is necessary for durability in cold climates. It is rare for air entraining compounds to be added to site mixed concrete. Sometimes contractors neglect to order air entrained concrete. Generally, people mixing concrete on site usually are not aware of what is really important about materials, mixing and finishing.

Salt is none of the biggest enemies of concrete - just ask your local highway department. The old fashioned rock salt (sodium chloride) is one of the worst de-icers. Other de-icers are not nearly as distructive.

Color matching is difficult if you don't know what materials were used initially. Usually you have little control over the materials can get, so you are at someone elses mercy. There is a difference in the color of different brands of cements.

In general, the cement producing process has changed somewhat as the international firms that purchased old American companies modernized the facilities. Also, there are changes in the manufacturing process required by government ecological requirements and there is a growing use of fly ash as a cement replacement. High performance concrete is now produced using fly ash and silica compounds to increase durability.

You can match a color of concrete today, but the new concrete will be a different color later. Concrete changes color as it cures - and it continues to cure for years if moisture is available. Generally, concrete internally lightens as it cures. As time passes the surface gets dirty and the cement paste wears off, letting you see more of the aggregate. If the aggregate is dark, the concrete can become darker. If the aggregate is light, it can become lighter. As the cement paste wears off the surface, the concrete appears more tan, since most aggregates are not a gray as the cement.

Dick
 
 

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