Concrete Hardener Compound: it is used to harden the paver and concrete blocks quickly so as to make easy and early removal of moulds and it also gives a touching finish to the bloks and fine mould impressions over the tiles. Accelerating concrete admixtures are used to increase the rate ofconcrete strength development or to reduce concrete setting time.Accelerating admixtures are especially useful for modifying the properties of concrete in cold weather.