Exposed aggregate concrete serves two purposes; it is both decorative and functional. It is a term used to describe a concrete surface, such as a floor, path, pavement or parking lot, that has exposed gravel. This method is used to create flat surfaces that not only look good, but they also provide extra grip in wet conditions.
Exposed aggregate concrete is made by removing the top layer of cement and fine aggregate from freshly-poured concrete. This leaves the large aggregate particles (crushed stone or gravel) exposed and sticking out the top of the surface slightly. It is a durable and skid-resistant surface that is often used to make driveways, paths, pool decks and floors safer.
Methods for creating exposed aggregate surfaces
There are many ways to create these types of surfaces, but contractors generally use four methods.
- Standard – The standard way to create exposed aggregate surfaces is by mixing a normal batch of concrete; cement, sand, water and crushed stone. The concrete is then poured and left for an hour or so to harden slightly. A broom is then used to vigorously sweep the surface, removing the fine concrete particles and leaving behind the exposed gravel and stone particles.
- Seeded – This method involves placing the gravel or crushed stone, by hand, into the surface of freshly-poured concrete. It is similar to planting seeds in the ground, except that just the surface of the stone is left sticking out the top of the concrete.
- Topping – Also known as a concrete overlay, this method is used to upgrade and existing concrete surface into a slip-resistant one. A fresh concrete batch is mixed and poured thinly on top of an old floor or path. The thin layer of concrete leaves the thicker stones exposed along the surface.
- Polished – This method is often used inside homes and is more decorative than functional. Instead of leaving the aggregate exposed with a textured surface, a grinder or sander is used to flatten the surface and make it level. Several layers of clear coat sealer are applied to create a shiny, polished surface.
As a general rule, the exposed gravel should always be at least two-thirds embedded in the concrete. This will prevent the stones from lifting and being removed from the surface, which would leave holes and large pits in the concrete. These pits can then collect dirt, water and soil, which can affect the durability of the floor.
Benefits of using exposed aggregate concrete surfaces
There are a number of reasons why people choose to use exposed aggregate surfaces in their homes and gardens. Firstly, it can look really nice if you use stones of various shapes and colours. Some homeowners like to match the colour of the exposed stones with the rest of their furniture. This makes it a customisable and aesthetic feature of a house.
Exposed aggregate surfaces are also very durable. They have the structural integrity of concrete and can last for 40 years or more. These surfaces are also highly-resistant to wear and tear and heavy traffic use. They can also handle exposure to the elements really well – sun, rain and hail have little impact on the strength and durability of these surfaces.
As with concrete floors, exposed aggregate surfaces require little maintenance besides sweeping and hosing with water. This makes them a cost-effective solution for floors and driveways. They don’t cost too much to install and they are certainly not expensive to maintain.
The main benefit, however, is the skid-resistance and added grip of the exposed aggregates. These surfaces are useful in wet conditions or around swimming pools. They ensure the safety of users, preventing slips and falls which could lead to serious injuries. Exposed aggregate concrete surfaces are safer than many other flooring materials, especially when wet.
LafargeHolcim is a leading building materials and solutions company that has been operating in international markets for decades. We produce cement and aggregates for construction projects, ranging from small affordable housing developments to large-scale infrastructure projects such as high-rise buildings, dams and bridges.
LafargeHolcim Tanzania has been supplying the country and neighbouring countries with our world-class Tembo cement brand for over 30 years. Our head office and fully-integrated plant are located in Mbeya, Southwest Tanzania.
At LafargeHolcim Tanzania, we believe customers come first. We listen to your specific requirements to supply and develop the best solutions for your needs. As the new leader in building materials, you can also rely on our cutting-edge research and development capabilities that have resulted in the finest materials for your construction projects, whether large or small.