Exposed aggregate is a classic decorative finish for concrete. It is arguably the oldest form of decorative concrete, dating back to the early 20th century. Exposed aggregate is a versatile finish for flatwork, vertical applications, and as a component of larger, more complex projects.

Exposed Aggregate borders on a large residential driveway.

Exposed Aggregate borders on a large residential driveway.

As a finish, exposed aggregate has a number of advantages:

  1. Skid Resistance – a non-skid finish is highly desirable for most concrete applications, especially outdoors. Even at a very minor exposure level, the added grit or texture is enough to improve traction. This makes exposed aggregate ideal for pool decks where standing water would otherwise pose a safety risk to swimmers. For this reason, exposed aggregate is also very attractive for sidewalks and driveways in wet and/or cold climates.

  2. Versatility – exposed aggregate is a flexible design option. In its simplest form, a continuous exposed slab, exposed aggregate concrete can benefit from an unending combination of color, aggregates, and exposure depths.

  3. Design Flexibility – it’s not just for large, exposed slabs. Exposed aggregate has great potential as a component of larger, more complex designs. Exposed bands and borders add a great deal of class and sophistication to more traditional hardscapes and stamped concrete. Exposed aggregate can also be used to spruce up tilt-up panels and some precast concrete installations.

  4. Low Maintenance – even by decorative concrete standards, exposed aggregate is easy to maintain. Occasional cleaning and resealing is all you need. For all intents and purpose, the maintenance is roughly that of traditional, non-decorative concrete.

  5. Timeless – because it has been around for so long, exposed aggregate has become a classic, timeless design. With an exposed aggregate patio, or walkway, you do not need to worry about changing styles and trends.

Exposed Aggregate used in a public plaza surrounding a fountain.

Exposed Aggregate used in a public plaza surrounding a fountain.

Another beauty of exposed aggregate is the ease of installation. There are a several ways to exposed aggregate:

  1. Brushing & Washing – this is the original method. While the concrete is setting, spray the surface with water and brush away the surface cream until the desired exposure is achieved. This method is very time-sensitive and labor intensive, so it is not well suited for large jobs. There is also very little room for error with this method.

  2. Media Blasting – using a sandblast, shotblast, or other abrasive, the upper layers of the fully cured concrete are removed to expose the aggregate.  This method is not as time-sensitive as Brushing & Washing, but it is similarly labor intensive and unforgiving. This method can also dull or damage the aggregate, which is not ideal for decorative applications.

  3. Surface Retarders – these chemical solutions come in a wide variety. Despite this diversity, they all operate on the same basic principle. The retarder is spray-applied during the finishing process. After a predetermined amount of time, applicators use a pressure washer or scrubber to remove the uncured paste and expose the aggregate. For jobs, large and small alike, this is often the best option. Surface retarders reduce labor and increase controllability and consistency. Make sure to do your own research and testing as not all surface retarders and made equal.

Surface Deactivator is the exposed aggregate surface retarder from Solomon Colors. It is just one of the many products offered by Solomon Colors to make exposed aggregate better. Surface Deactivator offers more control and consistency than sugar-based retarders. Surface Deactivator halts hydration to a predetermined depth, meaning the exposure will be the same independent of time. Because Surface Deactivator only retards curing to predetermined depths, the concrete paste below that depth retains its strength and prevents aggregate popouts. Surface Deactivator is the easiest way to expose aggregate.

A close-up of a fine aggregate exposure next to stamped concrete.

A close-up of a fine aggregate exposure next to stamped concrete.

Solomon Colors offers other products for your next exposed aggregate job. DAY1 Finishing Aid, for example, improved finishing and surface curing for a more even and consistent exposure. Solomon Color integral colors give the concrete high-strength, permanent color. Brickform water-based stains can highlight and mottle for a unique or aged look. Brickform sealers keep it all protected and attractive for years to come.