SKA Rugasol-90 Surface Retarder 10LSika Rugasol 90 is a specially formulated liquid surface retarder for summer conditions. Sika Rugasol 90 will cause retardation to the surface of the freshly laid concrete, and can be used to achieve an exposed aggregate type finish. The retarding compound in Sika Rugasol 90 combines with cement at the surface and delays the normal hydration on the surface of the concrete (high cement contents and temperatures will reduce the retardation). After