Crumbling Front Porch - Part 2 - The Repair
 

I posted a few questions at the below link about 2 weeks ago.

http://www.diychatroom.com/f2/how-re...-mortar-67723/

I have now done my best to pull out all of the bricks that had come loose (there were quite a few more than I thought) and found some bricks that closely (but not exactly) matched the old bricks. I also purchased a diamond saw blade that was on clearance to cut out some of the old concrete. I originally thought that the concrete was only about 1 1/2 inches thick because of the condition under it but it turns out what I thought was sand was pulverized concrete and morter. Once I started cutting back all of the damaged concrete I found that the concrete is actually about 4 inches thick. Now I need some advice.

I was thinking that I would mortar the new bricks in place and put the concrete cap back on. Then pour fresh concrete into the gap between the concrete cap and the old concrete that I trimmed back. I think this should insure that there is no gap between the cap and the concrete for water to get into. Any advice or thoughts on this would be appreciated.

The other question is this: Should I drill into the old concrete and cement in some pieces of rebar to tie the old and new concrete together or is that just overkill. The person at ACE hardware showed me some kind of adhesive that you brush onto the old concrete that is supposed to adhere the new concrete to the old. What is the preferred method for making sure that the new concrete doesn't just pull away from the old next winter?

The picture below show what I am dealing with.

This picture shows what I am dealing with after removing all of the loose and crumbling concrete.
http://farm3.static.flickr.com/2255/...40a4b55e0f.jpg

This is a close up of the chiseled away concrete. What is left there seems to be pretty solid. It wasn't breaking up without a lot of effort.
http://farm3.static.flickr.com/2097/...58ce886260.jpg

I used the diamond blade to cut this section of concrete back because the railing was making it impossible to swing a hammer and chisel. The concrete is actually thicker than just the smooth cut section. That was as deep as the blade would go so I cut out what I could. Under the smooth cut it feels like more concrete. The chisel was having a heck of a time breaking anything up down there.

http://farm3.static.flickr.com/2698/...84d308bee0.jpg

This is the same section as above but from further away. You can see it was a fairly long strip that I had to cut out to get all of the damaged concrete.

http://farm3.static.flickr.com/2169/...b6c7bf9601.jpg

This is the stuff that the guy at the brickyard suggested for the bricks.

http://farm5.static.flickr.com/4002/...8350f98ac3.jpg

This is the concrete that I picked up from Lowes. I would be very appreciative if anyone has any better suggestions for this.

http://farm5.static.flickr.com/4054/...cb7653ff0c.jpg

The only cure I know of for crumbling concrete, is to remove all of it. Half measures never work for long. And if part of it is crumbling, more will follow.

Would this be the case even if the crumbling areas are limited to fairly small areas? I have been pretty aggressive about chiseling out everything that feels soft so that was is left is still very solid. These were areas that appear to have suffered a crack which then allowed water to enter. The freezing temperatures we had this year popped the concrete out. These were all places that the original homeowner had repaired before but it looks like all he did was take the chunks of concrete and mortar them back in place. I am hoping by cutting the bad concrete out and pouring in fresh concrete (the way the state fills potholes in a road after a bad freeze) that it will be a longer lasting repair. I hope I am not wrong.

Having seen the photos, it looks like 4" of new concrete was poured over a flagstone terrasse, judging by the profile I see and the fact that the railings were anchored onto a flagstone-looking surface. Now that in itself may not be bad but common sense would dictate that first, the railings are now 4" shorter and therefore maybe out of code and second, will the underlaying surface withstand the extra weight.

I think most conscientious contractors would have removed and replaced the railings, so that tells me there may have been other shortcuts taken to save money, which may or may not have given rise to your particular problem.

So there may be other issues for which Bill's advice might be appropriate; but if you ask whether or not a patch would benefit from rebar and/or adhesive, then personally I would say yes to both.

First off I will say you are absolutely correct that shortcuts were taken by the previous owners. I have owned this house for less than a year and I can already tell that when they had the option between completely 100% cheap vs. sort of 99% cheap....they always went for the 100% cheap option. Our neighbors even told us that they talked to the contractor when he was originally building this porch and the contractor told him that porches really weren't their thing and that this was their first raised porch. Now I know that that is all hearsay but judging by the quality of the rest of the "improvements" made on the house I can believe it.

Regarding the porch construction. The underside is actually not flagstone (or at least what I understand flagstone to be). They appear to be reinforced concrete panels. It looks like they were laid down first over some brick piers and a steel i-beam to form a base for the poured concrete. I have some pictures below:

This shows the edge of two of the panels and how they join together. Judging by the rust spots I would assume they are reinforced with rebar.
http://farm5.static.flickr.com/4015/...513bcf1db1.jpg

This is an image from underneath the porch. This is where it extends out over the driveway so you can see the individual reinforced concrete panels. Keep in mind that the poured concrete is laid on top of this. It actually went: panels ---> layer of sand ----> poured concrete.

http://farm3.static.flickr.com/2121/...240d7c1812.jpg

This is an image showing the panels being supported by a steel i-beam (which is rusting suggesting another project - grinding, priming, and painting).

http://farm5.static.flickr.com/4006/...6aa84c36a4.jpg

Ah-ha, I see. I think it's moot but a teardown solution may be killing-a-flea with-a-shotgun and will depend on your ability to live with the problem and the health of your bank account, neither of which I have data on. You could spend $xxxx on replacing it all and doing it differently - or $xx on a patch along the lines you suggest.

You may even be back to do it again in 5 years - but for the $ difference, I'd patch it.

Do you happen to know what the purpose of the layer of sand is between the poured concrete and the reinforced concrete panels? One of the problems was that when a crack formed the water entering the crack was washing the sand from underneath to the edges and then the waterlogged sand was freezing forming the blow outs. I was thinking that I would pour this edge so that the poured concrete rests right on top of the concrete panels, thereby preventing the sand from washing out. Would this make it impossible to tear out the poured concrete if/when it ever cracks again due to the poured concrete adhering to the concrete panels? Is that the purpose of the sand layer....to prevent the poured concrete from bonding with the concrete panels?

It floats or de-couples the uppper layer from the firm base.

So I guess that would suggest that the sand is necessary.

Yup. It's because two different materials, say one being a solid concrete block and the other a metal frame, will respond differently to hot and cold temperatures and one may flex more , or twist more, or expand more or less than the other. When one materials puts stress on the other, they can crack.

So, yes it is necessary; it's a big issue in tiling, for example of floors and shower walls and exterior patios.