Around the end of Victorian, and the beginning of Federation architecture in Melbourne is where I begin to find cementitious (cement based) mortar and render mixes. Which places the popular introduction of cementitious products around the decades of 1890 - 1920.

The phasing in of cement materials throughout this time means that most of these heritage builds still focused on the use of lime putty as the base, and the new cement product was largely an inclusion as a setting catalyst.

While consulting or breaking out on a project, if I find the tensile strengths of the removed ruble show cementitious composition, I know its a good idea to keep digging. This is to remove more of the damaged plasters, renders, mortars and even bricks, to reveal the original works of the building. Its here where the building will tell me to what degree to include cement in the repair process.

Where heritage materials are of cement included composition, they require all further repairs to be completed with a mimicking material. Just as lime based materials are more chemically compatible with lime based sub-straights and sub straight materials, cement included materials are also more chemically compatible with cement included sub straights and materials.

The second critical element to this process is mimicking the tensile strength of the original materials. Due to modern cement products being thoroughly refined, they are far harder once set and cured than heritage cement materials. Careful attention to detail is required when composing a cement included mixture to mimic a heritage material. For instance, a heritage mimicking mortar mix may look something like: 9 sand, 2 lime putty, and only 1 cement. + adequate curing.

The third element to working with all heritage lime and cement included materials is curing. Having a mortar, render or plaster dry too quickly is a terrible thing. For the lime and cement have not gone through their necessary curing process slowly which produces a far better quality repair for several reasons.