OPTIMIX SF818 Self-Levelling Screed (Underlayment) is a high quality pre-mixed mortar consisting of special cements, graded aggregates, selected fillers, polymers and plasticizing additives. When mixed with water, it readily blends to produce a flowable and pumpable mortar for floor screed. It can be applied at thickness between 3mm and 20mm in one operation to provide a levelled and flat floor surface. OPTIMIX SF818 can be applied to all concrete substrates. It is designed to replace the traditional hand applied site mix sand cement floor screed.