Is Portland cement a good choice?
Where the walls are damaged there is nothing left but a powder on the floor, so I don’t know what originally was used. The major argument against using Portland cement is that there are trace elements of tricalcium aluminates in the mix, which can form damaging salts between the brick and the stucco. In fact, the wall coating you are describing is not a true stucco, nor was it intended to be a waterproof covering. What you have is a sacrificial coating called a parging or a pageting and it most likely is made with a hydraulic lime and sand, which is why it turns into powder when it fails. Hydraulic lime was mixed with a fine sand and animal hair was used as a binder to make a lime plaster, which then was used to coat and protect the brick. At the same time, the plaster allows for the free flow of water vapors through the brick wall. The term “sacrificial” indicates the lime plaster is intended to fail over time in order to protect the bricks and the mortar from the ravages of time. The
