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My old steel posts had rusted and caused the concrete to crack then expel a wedged chunk of concrete. There isn't a lot I can do about the cracks but would have to repair the holes whichever way I decided to move along to.
I had the choice of removing all the steel posts or repairing them. I decided to repair the concrete and replace two of the posts.
I have repaired pebblecrete before that has had the same type of deal happen but nothing this size. The specs of the concrete said up to a40nd 150mm max depth (Tho I cant find it now)
I drilled 6 holes into the concrete slab at various angles to give something for the concrete to bind to. I used Concrete anchor bolts, 50mm and 75mm long for the various distances I would need.
Materials
Concretemate 4kgs 2 of
75mm Concrete anchor box 10 (8mm)
50mm Concrete anchor (8mm)
1L Dulux Metalshiled Epoxy Enamel
Sheet of laminated mdf
Tools
Spanner
Grinder
G-Clamps (multiple)
Wire brush
Cold chisel
Steps
Step 1
I had been putting off this job as it was into an area I wasn't confidant of working. I have concreted before but only posts into holes. Not repair something at eye level.
First step was to remove the old hand railing and any of the flaky bits of concrete from the broken sections. I used a wire brush and a cold chisel to make sure nothing was loose in the holes.
The old handrails and their posts.
The rust had cracked and then blown out the concrete.
Hanging in the breeze :o. Even tho I walked past it everyday I hadn't really thought it as bad as it was until I dismantled it.
Before shot...
I was concerned about how to patch this so it would be structurally sound.
What hid it from eyesight until I looked closely. Then levered with a screwdriver and bingo...
Temporary handrails so I wouldn't walk off into space.
Really did a job on the rust verse concrete...
The post popped right out easily.
Apparently the yellow is sulphur which they use to use to bond the post to the concrete. They would drill a hole, and put the sulphur in and then the post. Well according to an older mate of mine.
Rust really eats things away. Tho this is around 40 years worth Id say.
Hole cleaned and chiseled of loose matter
Second hole cleaned. Sulphur scrapped out.
Step 2
I looked into a few different types of concrete and concrete repair kits And decide on concretemate as being the strongest at 64Mpa after a week. I drilled horizontal into the slab and randomised the angles. I then used 7.5mm Masonry anchor screws and only screwed them half to two thirds into the slab. This was to give the concrete something to bind to.
I used two 4kg containers worth. I thought it was going to be a paste like substance but its a dry concrete powder. One thing to note "Less is more when adding water" even less then what is recommended as a mix to start with.
I used 75mm and 50mm Masonry anchors into the slab.
I painted the steel posts with this to protect from rust.
For future reference in case I need to remember what I used.
A sheet of laminated board I bought to use for the formwork. I had various suggestions to stop the concrete sticking to the timber but this solved the issue in one go.
The concrete anchors screwed in at various angles. Making sure to keep 20mm from the edge as that is what the product said.
Second hole which was larger.
Formwork in place. It fitted nicely. I did use the front of a cornflake packet as a wedge at the back to stop concrete coming through. It worked and haven't seen any issue with it so far.
I couldn't do anything about that crack but it seems to be solid. The screws show up nicely tho.
My supporting structure to keep the posts vertical and in place as the concrete cures.
From the side. Pretty happy with the setup. Tho the sun was dropping fast at this point. I was lucky enough that work had a little left over 20*20mm steel posts.
Made sure the post was clamped vertical
The sun disappeared fast, the concrete was going off fast. But it went fairly smoothly. I ended up having just enough to do both holes. I had to add more concretemate powder to the first batch as I had added too water too fast.
It does cure fast. It was dark and I was nervous is my only excuse. I was happy tho. I tapped the side of the formwork to remove any air bubbles in the concrete.
I thought I had smoothed it more so but still happy with it.
Step 3
I left the supports in place for 3 days but it started to sprinkle so I removed the timber stands.
I let the concrete cure for 5 days before removing the formwork. The concrete came out like a bought one! Well bought by someone who has had no real experience in concreting and it turning out nicely. I should have smoothed it more so on the night I did the work is about all that I would change.
The morning after the pour.
The morning after the pour. It gradually dried over the next few days (They were cold days but no rain)
After the supports had been removed.
About all the rain that sprinkled.
Very happy with the outcome.
The concrete look so nice and really smooths in well with the old concrete.
This was the better looking side.
I brushed it back with a wire brush and used a cold chisel and hammer to take off some high pints and blobs.
I couldn't believe how nicely it turned out.
The roughness is from me thinking it was smooth but not.
Not particularly rough but not smooth either. Still happy with the outcome as I did heavily chisel bits around it and it held up to the knocking.
The nicest part... All four top posts are in a straight line! One of the major things I was worried about. Next steps are to remove the flaky paint on the concrete surface, remove the flaky paint from the around the front door and put up the timber for the handrail.
It will be a few weeks before I get to the point of buying the slats (need to save some money lol) I will be working on the doorway and stripping it back for the time being. Yeah lateral stresses have been up there on my list of worries. Its one reason I was so happy to see the posts all lined up (they disappear behind each other) Def will be waiting a few more weeks. Thanks for the compliment 
Dave
Good Evening @Gillie1
Thank you, I find it helps to break a project down into smaller sections and focus on them as you get to them. Way less scary that way.
Dave
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