Repair of concrete retaining wall in stairwell, below school building (Activity Report)

WHILE A CONCRETE-REPAIR CRAFTSMAN was doing repair work elsewhere on the premises in mid-September, he redid this old patch, as well. 

November 2023 
(As usual, click/tap on an image to enlarge it.)

For a description of the problem, see HERE.

Below the jump, this post documents what was done, as well as how one resulting concern was handled.…

Scope of work 

1. Remove loose concrete at the old patch.
2. Prime the exposed rebar using a top-quality anti-corrosion primer (Sika Armatec-110 EpoCem = a cementitious epoxy-resin coating material with corrosion inhibitor, used as bonding primer and reinforcement corrosion protection).
3. Rebuild the area using a high-quality patching material (SikaQuick VOH = a cementitious, polymer-modified vertical repair mortar).

The craftsman told me that the old patch used cheap materials and was not properly done. He expressed confidence that the new materials would wear well.

September 18, 2024

A few days after the patch was redone:

I had told the contractor (Mark Beamish Waterproofing) not to be concerned with the aesthetics, since this stairwell is not used by members (except as an emergency exit from the basement). That’s why it’s not very pretty, to say the least.

October 31, 2024

About 6 weeks later:

I noticed that white spots (efflorescence) had quickly appeared near the edges of the patch. I asked the contractor about it and sent this photo. At first, we were both concerned that perhaps there was an otherwise unknown water source underground that was making the patch wet from behind. 

So they sent over one of their experienced managers to take a look. 

He told me that the efflorescence was not unusual—basically a part of the curing process—and nothing to worry about. He predicted that a hard rain would wash away the white spots. (Alternatively, we could wipe them off with a wet towel.)