Retarder

 

Application:

Surface retarder is either painted or sprayed onto the casting surface prior to production.  Once retarder has cured, concrete is poured directly over coated casting surface.  The retarder delays the curing of the concrete paste where interacting with concrete.  Post-production, finish areas are power washed, removing concrete paste and exposing aggregates at intended locations.

Finish Exposure

Retarder exposure is per the specific retarder manufacturer specifications.  Most retarders are available in light, medium and heavy exposure depths.  Retarders are typically used when medium or heavy exposures are specified as the application process does not have an abrasive impact to the exposed aggregates.

Pros:

Since retarder is coated on the casting surface, retarders can be used when only specified areas of the surface need to be textured.

Design Considerations:

Retarders should be used on deeper finish applications where the bright, natural color of the exposed aggregate is the primary concern.  The mixture proportions, aggregate gradation and physical characteristics of the aggregate, and matrix/aggregate color

compatibility are important. It is advisable to vary the color or tone of the matrix wherever possible to match or blend in with the color of the aggregate. This match

can be achieved by careful selection of cement, sand, and pigment colors. A good matrix to coarse aggregate color match will minimize mottled effects.