How to pour exposed aggregate concrete

How to pour exposed aggregate concrete

Both solid concrete (with a standard tooled finish) and aggregate driveways are durable, long-lasting options. Aggregate driveways are commonly known as exposed aggregate because the gravel (or stone chips, in some cases) in the concrete mix is partially exposed in the finished surface. Aggregate variations allow you to add color and texture to your driveway, creating an eye-appealing design that coordinates with your house and landscaping. A standard concrete finish is relatively smooth and for a driveway typically includes a broom finish for slip-resistance.

Decorative Differences

Exposed aggregate and standard concrete driveways have very different looks. Exposed aggregate is multicolored (due to the natural color variation of the aggregate material) and highly textured. According to Shamrock Concrete, the tops of exposed pebble and rock are approximately 1/16- to 1/8-inch above the base concrete surface of the driveway. Standard concrete can have the familiar flat, gray finish but can also be colored and/or textured with stamping techniques and other decorative treatments.

Installation Procedures

Expect a somewhat longer construction process with aggregate driveways. Once an aggregate driveway is poured and smoothed with a trowel, but while the surface is still wet, installers spray it with specially formulated chemicals. The chemicals keep the top layer that surrounds the small pebbles and rocks from solidifying. The surface is covered with plastic sheeting for approximately 24 hours to help keep the top concrete layer from hardening. Once the plastic is removed, installers power-wash the surface, removing the top layer of soft, paste-like concrete from around the small pebbles and rocks. The result is an exposed aggregate surface.

Deterioration Factors

Both standard and exposed aggregate concrete driveways are highly durable, but many installers recommend sealing the surface to ensure longevity. Aggregate driveways are especially susceptible to weathering and deterioration due to their textured surfaces. When weathering happens, small stones and pebbles dislodge and break apart from the underlying concrete foundation, causing damage that is often irreversible, according to experts at the Stain and Seal Company. All concrete structures are vulnerable to cracking. Small cracks should be filled with an appropriate sealant to prevent further damage. Large cracks and shifting sections of a driveway are more serious and often indicate a problem with the subbase under the concrete.

Maintenance Considerations

Due to the uneven surface of aggregate driveways, you must hose them down frequently to retain their optimal appearance. Sand, dirt, grass clippings, leaves and loose flower petals can get trapped in the surface, making the driveway appear dirty and dingy. However, you don’t want to use a high-force power washer that might dislodge the small pebbles and result in small gaps or holes. Standard concrete surfaces get dirty, too, but you can use power washers without cause for concern, as long as the surface isn’t cracked.

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You would have surely seen decorative driveways, sidewalks and patios and perhaps wondered how they are achieved. Those are achieved by using exposed aggregate concrete. Those floors are done by removing the top layer on concrete from a surface to reveal the color and texture of aggregate beneath it. Exposed concrete floors are durable and provide skid resistance.

ADVANTAGES OF EXPOSED AGGREGATE CONCRETE

There are both pros and cons of using exposed aggregate concrete. The advantages include:

  • Get gorgeous decorative effects at an affordable cost as very few additional materials are needed. You may will only need some decorative aggregates, surface retardant, sprayer and a garden hose. So, exposed aggregate concrete is not expensive.
  • The construction procedure is quite simple and anybody experienced in handling concrete can do it.
  • The surface is weather resitant, lasts long and also skid resistant.
  • There are variety of decorative aggregates like small or large size, round, colored etc available.
  • It suits with the other decoratives around.
  • No additional maintenance except occasional cleaning with water and resealing every few years.

HOW TO DO

Here are the three ways of having aggregate exposed concrete:

Monolithic – This is the easiest and hence the most popular way of making such floors. The aggregate is batched into concrete at the time of making concrete. Smaller aggregate known as ‘pea stone’ is generally used.

Seeded – Soon after concrete is laid, the decorative aggregate is mechanically or manually placed over the surface of concrete and floated by hand.

Overlay – This method is suitable for already existing concrete in good health. Aggregate is mixed in the overlay material and applied over the old concrete to give it a new look.

How to pour exposed aggregate concrete

In any case, the top layer of the cement paste is kept soft while the concrete below it hardens. This is done by spraying a retardant on the surface immediately after concrete and aggregate have been installed. Subsequently, the cement paste is washed clean using a garden hose or pressure washer to expose aggregate on the surface. You can read this post about making exposed aggregate concrete . exposed aggregate concrete

DISADVANTAGES OF EXPOSED AGGREGATE CONCRETE

While an exposed aggregate concrete adds color to front yard or driveway and looks exclusive and ornamental, compared to concrete slab, you need to consider its limitations before installing one. The disadvantages of exposed aggregate concrete is listed below.

Durability

Though exposed aggregate can be tough and long lasting as long as the concrete holds together the aggregate, the decorative stones on top are prone to damage. Movement of heavy objects and water damages can dislodge or loosen the stones close to the surface to create small pits therein. And, once the process starts, the damage spreads pretty fast as surface water deteriorates the bond between the concrete and aggregate.

Repairs

Repairing a part of such floor is more difficult, compared to repairing cracks in concrete floors . The toughest part is blending of the patched surface with the rest of the floor. You may tint the patch of concrete to go with the older concrete and then fill that hole as in case of concrete surface. Avoid using excessive amount of compound to fill the hole to make easy the leveling of the affected part with the rest of the floor. Subsequently, add stones to the new concrete. You’ll need to find aggregate that best matches with your existing surface.

Maintenance

How to pour exposed aggregate concrete

Cleaning exposed aggregate is certainly more difficult than cleaning of concrete slab that can be hosed off. Dirt and debris gets stuck between its surface, necessitating using wire brush or powerful jet of water for their removal. Whether you have exposed aggregate surface on the walkway, driveway or patio, it needs sealing once in two years to enhance its life and strength. exposed aggregate concrete maintenance is difficult

Nevertheless, on comparing with other decorative concrete styles; it is realized that exposed aggregate concrete offers an economical way of having a great looking decorative concrete look.