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. It is a proprietary pre-blended cementitious self levelling screed comprising cements, aggregates, modified polymers and additives, to BS EN 13813 and is suitable for foot traffic without floor finishes or with selected finishes. Formulated with low shrinkage to reduce cracking, it can be poured or pumped in thicknesses from 3mm to 20mm in one operation.