The primary purpose of the Autoclaving is to transform the green cake into white cake. This transformation takes place in autoclaves, where the green cakes are left for curing. The actual curing takes place by filling the autoclave with pressurised steam (saturated water vapour) supplied by the boiler. It is during this environment where the most reaction will happen between the sand or PFA and therefore the binding agents lime and cement. This reaction, which results in the forming of calcium silicate hydrates within the cellular concrete’s matrix, takes place in two reaction phases. In the first phase, a topochemical reaction takes place during which the lime and silica acid are the reactants. Water doesn't happen within the actual reaction; it’s only built into the new formulations that are formed. These reactions occur within the border areas of the raw materials, starting at the active spots (e.g. on the edges) of a crystal. The second phase of the reaction