Mixing pea gravel or any other type of rock into concrete is a technique known as creating exposed aggregate. Quite simply, this means that when the concrete is dry, the pea gravel is exposed at the surface, thus creating a texture. Combining pea gravel with concrete is an effect most frequently used for driveways, patios and other outdoor locations. Mixing the pea gravel into the concrete is not difficult, but it does require a little work.
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Things you need
- Garden hose
- Spade or trowel
- Pea gravel, 1 cm (3/8 inch) in diameter
- Lawn roller
Fill a wheel barrow with 6 to 8 gallons of pea gravel and then use a garden hose to fill the wheel barrow up with water.
Stir the pebbles for approximately 60 seconds using a small spade or trowel. This removes any dust and debris from the gravel that may interfere with the mixing process.
Tip the wheelbarrow up slightly and allow the water to drain out over the edge. Pour more water into the wheelbarrow and continue washing the pea gravel until the water runs clear. Repeat until all of the pea gravel has been washed.
Place wooden form boards around the perimeter of where the concrete will be poured. These act as barriers to keep the concrete contained until it sets.
Mix the concrete according to the instructions on the packaging.
Pour the concrete into the area between the wooden forms until it reaches 6 mm (1/4 inch) below the top of the board.
Insert a screed on top of the concrete surface, but in between the wooden form boards. Drag the screed along the entire length of the concrete to create a smooth surface. A screed is a long wooden board.
Smooth the entire surface of the concrete using the flat edge of a trowel.
Allow the concrete to sit until no water is visible on the surface. This may take anywhere from a few hours to half a day. The concrete is ready when you can place a pail of rocks gently on the surface and it doesn't sink in. A slight indention will be made by the bucket but nothing more.
Fill the bucket with pea gravel and tip the bucket slightly to distribute the pea gravel lightly over the surface of the concrete. When the bucket is empty, refill it and continue spreading the gravel until the entire surface is covered. You will need approximately 3.8 litres (1 gallon) of pea gravel for every 90 cm to 1.5 m (3 to 5 feet) of concrete.
Drag a broom over the entire surface of the pebbles to spread them evenly across the concrete. There should no areas larger than a penny that do not contain pea gravel.
Place a lawn roller on top of the gravel and roll it over the entire surface of the concrete to press the pea gravel into the concrete. The pea gravel should be pressed evenly with the surface of the concrete.
Allow the concrete and pea gravel to sit until the top surface no longer appears shiny and wet.
Sweep the entire surface with a broom to define the pea gravel. As you do so, a thin layer of concrete will be swept up to expose the top edges of the pea gravel.
Spray the surface of the concrete gently with a garden hose held at an almost horizontal angle to the surface. This washes the concrete residue off of the pea gravel to reveal its natural colour and shine.
Allow the entire surface to dry completely before using.
Tips and warnings
- Large sheets of plywood can be placed on top of the wet concrete to access the middle surface areas when needed.