What's the best way to prepare foundation spalling for repair?

Question

I have some foundation damage that I'm planning to repair using a simple mortar maybe with something added to strengthen the bond to the existing concrete. The damage is from water reaching the bottom plate anchors, and the concrete popping when they rusted. I had most of the similar damage repaired recently but a couple places hidden by a structure were missed. Rather than call the mason to fix the two or three places that still need patching, I'd like to try tackling it myself.

My question is about what products to use. When the other damage was repaired recently, the mason prepared the concrete by spraying in a milky substance that he said both etched the existing concrete and stopped any rust (although he cut the dangling anchor bolts out too). Any idea what the product would have been? The rust preventative might be important since one patch will be over the old sewer line (see photo). Also, what is the best cement to patch with? The mason said he was using simple portland cement mixed like a mortar which he applied in layers over two or three days. Would mortar be the best bet?

Answer 1

Acids that will etch concrete will also remove rust, so the combo doesn't narrow the selection. The most common acid used is muriatic acid which is diluted HCl and available at most hardware stores. There are also muriatic blends with sulfuric or phosphoric acids added, no idea if they are better or just marketing.

However, you should follow the manufacturers instruction for whichever cement or epoxy produce you end up applying. They may specify what they prefer you use for best results. If instructions are vague or not included, call customer service and ask. If thats a dead end I would tend to use straight up muriatic acid.