3 Ways Through Which Precast Concrete Can Have an Exposed Aggregate Finish

You can ask a concrete contractor to supply you with precast concrete panels that have an exposed aggregate finish so that your new warehouse can be unique from the buildings near it. This article discusses some of the methods that can be used to achieve that exposed aggregate surface finish. Use this information to select the most appropriate method to finish the panels that you want to order.

Chemical Retarding and Sandblasting

The first way to achieve an exposed aggregate finish on precast concrete panels is by applying a chemical retarder on the surface of the forms where the concrete panels are being cast. That retarder prevents the concrete on the surface from setting at the same pace as the concrete in other parts of the forms. The concrete far from the retarder is allowed to set before the forms are removed and the surface is sandblasted to expose the aggregates underneath.

This method is ideal because minimal effort or resources are used to expose the aggregates in the concrete. This ease of application can translate into a lower quote to you. The surface of the precast concrete also has a uniform appearance once casting is completed. However, this method can't easily be used for concrete that is cast using vertical forms.

Chemical Retarding and Washing

A chemical retarder is also used in this method to stop the surface of the precast concrete from setting. The aggregates underneath that surface are then exposed by using a jet of water to wash off the finer materials, such as sand, in the concrete mix. This method is ideal in case you would like the exposed aggregates to be free from any forms of damage caused by the cleaning method used in the fabrication of the panels. The finish is also easy to patch in case imperfections are noticed. However, this method can only be used during the warm months of the year in order to prevent the water from freezing within the pores of the precast panels.


Exposed aggregate panels can also be made by sandblasting the surface of the precast concrete after the panels have set. This method enables the concrete contractor to determine the magnitude of aggregate exposure that will address the client's needs. For instance, deep aggregate exposure can be achieved by sandblasting the panels heavily so that the exposed aggregates form the most recognisable feature of the panels. Medium or light aggregate exposure can also be achieved using this method.

The method allows the contractor to etch the aggregates while exposing them. This finish is ideal in case you live in an area where large amounts of rain fall. Deep aggregate exposure allows the moisture to drain off the panels quickly. However, sandblasting is labour-intensive and expensive.

Discuss the options above with a precast concrete contractor so that you can be helped to select the best way to finish the surface of your precast concrete panels.