How to Repair Precast Concrete Panel

I have a garage constructed of precast concrete panels which are internally reinforced. Following a minor incident with a tree I had a reinforced precast concrete panel that was broken into 4 pieces. I can’t buy a new panel – so a broken precast concrete panel repair is required.

broken concrete panel needing repair

Preparation for repairing a broken precast concrete panel

We need a decent flat surface to work on to support the broken precast concrete panel during repair. A piece of heavy ply has been arranged on trestles to provide for a long work table.

The panel was reinforced, and the two reinforcing bars have been cleaned up by removing them with an angle grinder from all of the pieces of broken casting.

Superficial loose dust has been removed and all of the pieces checked to ensure they can be fitted reasonably closely together, and in what order they are best reassembled.

The two working areas have been protected with tinfoil. The filler that is to be used will stick the broken concrete casting to the plywood worktable given half a chance.

Once we are happy that all of the pieces of broken concrete panel  can be fitted together our precast concrete panel repair can begin.

Concrete Panel Repair – Priming the Concrete

Damp concrete primer will adhere tenaciously to the concrete, and will allow all manner of modern materials to bond firmly to it. This was a structural reinforced panel remember – and we are not able to put reinforcing bars into it as it once had.

First mix a little of the damp concrete primer with two parts water like so:

mixed damp concrete primer concerte panel repair

Then to start the broken concrete panel repair apply the damp concrete primer with a paint brush to the broken edges of the concrete. Only a thin film is required but thoroughly wet the concrete with the brush to ensure great adhesion of the adhesive filler we are to use.

apply damp concrete primer to broken precast concrete panel

Any pools of damp concrete primer are cleared up with tissue, and now we wait four hours.

Precast Concrete Panel Repair – Fill-It Epoxy Filler as Glue

After a four hour or so wait the damp concrete primer will be ready to take the filler.

Firstly mix our Fill-It epoxy filler thoroughly. Full instructions for mixing fill-it can be found here.

Now coat all broken surfaces of the panel with a film of the mixed Fill-It filler. Use a palette knife or scraper and spread it firmly into the primed concrete surface. We are aiming to get enough into the break that some is squeezed out when the panel pieces are forced together.

coat broken concrete surface with fill-it epoxy filler

Once all of the broken surfaces have been coated with Fill-It epoxy filler we can reassemble the pieces of our jigsaw. Our dry run showed us how best to reassemble the pieces, and once they are together we can apply significant pressure to put the pieces back from where they came, and to force any excess filler out of the cracks. our concrete panel repair is now starting to look good.

broken concrete panel repair nearly complete

The filler is then smoothed out to ensure the panel fits where it should, and to seal any exposed concrete edges against water ingress. This will help to protect against freeze-thaw damage as well.

broken precast concrete panel repaired

Final carving of the filler if required can be done the next morning, where the filler will be hard enough to carve with a sharp scraper.

Structural Concrete Panel Repaired

The finished panel is now ready for refitting – and whilst we cannot rebuild the internal steels, this repair should offer plenty of strength for the building to last many more years.

repaired concrete panel ready for refitting

The real trick here will be to try not to fell a tree on the garage again I guess…