Question - I have a painted concrete block retaining wall on the property line with my neighbor. When it rains, excess moisture forms a white powder on the wall, and its paint flakes off. How can I treat my side of the wall to stop the moisture seepage and prevent the paint from flaking? We were advised to tar the wall's back.
Drains were installed at the wall's base, but the clay in the soil seems to prevent the water from seeping down to the drains.
Answer - The white powder on the wall is a mineral deposit that forms when the water carrying the minerals evaporates. To prevent this, and stop the paint from peeling, you must stop the water from seeping through the wall by installing better drainage. Treating your side of the wall won't stop the problem.
You are correct in saying that the clay in the soil prevents the water from reaching the drain. Soil with a high clay content does not drain well. This soil should be evacuated from behind the wall and replaced with gravel. A perforated drain pipe should be installed and water will percolate through to the pipe. It is important that the pipe have a free-flowing outlet, to allow the accumulated water to drain.
Do not simply tar the wall's back and then backfill with the same soil - the tar will seal the wall and prevent the water in the soil from escaping to the outside. If the water builds up, it can exert enough pressure on the wall to crack it or heave it.
Question - How do I repair pitting and scaling caused by de-icing salts on my concrete garage floor?
Answer - There are two methods: Trowel a vinyl mix made from portland cement, sand and bonding agent onto the damaged area, or pour a fully bonded concrete overlay at least 1 inch thick over the entire slab.
If you plan to fill the damaged areas only, clean them thoroughly to remove the dirt and salt residue. Break away any unsound concrete in and around spalled areas. If you wish to overlay a new surface, first etch the old surface with a solution of 1 part muratic acid to 4 parts water. Or you can create a suitable bonding texture by using a sacrificer, grit blaster, scabbler, planer or flame cleaner. These tools can usually be rented.
Soak the old surface overnight. When you are ready to pour the overlay, broom on a bonding grout - a creamy mixture of portland cement, fine sand and water. Follow the grout immediately with concrete mixed in proportions of 1 part portland cement, 1 part sand, and no more than a 51/2 gallon of water per bag of cement. Cure the new overlay by keeping it damp and covering it with plastic or burlap for seven days.