Making your own concrete patio stones or paver bricks is a fairly simple step-by-step process. In addition, the available mould designs and concrete colouring agents allow you the freedom to design your patio or driveway to suit your personal tastes. Despite having to buy moulds and raw materials, plus investing time and effort by mixing concrete, filling moulds and curing the pavers, you will lower the cost of your paving project substantially by doing it yourself.
Cover the inside of the moulds with a barely visible coat of concrete release agent. Use a spray dispenser, and wipe off excess material with a sponge or cotton cloth. This will not only make it easier to remove the finished paver, it will also extend the mould's life.
Mix the amount of bagged premix concrete you require for immediate use. Use a sheet of thin plywood as a base to facilitate mixing. Pour some dry premix into a 19 litre (5 gallon) bucket and add the desired amount of light shaded concrete colourant powder. Mix thoroughly. Alternatively, add liquid colourant into your mixing water and stir well.
Pour the dry premix onto the plywood, and scoop out a hollow for water. Add water sparingly and mix thoroughly with a shovel to a fairly stiff mix. The mix should not be so thin that it flows like pancake batter, but it should be thin enough to settle into the contours of the mould. The consistency of sloppy mashed potatoes is about right.
Sprinkle a light dusting of darker contrasting powdered colourant into parts of the mould. Shake the mould to partially spread the colourant over the release agent. This will impart a random shading effect to the finished stone. If you wish, use a dry 1.3 cm (1/2 inch) paint brush to spread the colourant around in a random fashion. Use a light touch to avoid overpowering your lighter base colour.
Scoop the mix into the mould carefully. Try not to disturb the positioning of the colourant powder. Fill the mould to the brim if using a 3.8 cm (1 1/2 inch) deep mould for pavers or patio stones, alternatively pour to a depth of 1.3 to 1.6 cm (1/2 to 5/8 inch) with a scoop or an empty juice can if making tile or veneer stones.
Bounce the mould up and down on a solid surface to release trapped bubbles and to compact the aggregate. Excess water will rise to the surface naturally, and the back of the stone will become smooth and level. Do not remove excess water.
Place the filled moulds under cover or in a shaded area. Cover the surface with a sheet of thin plastic to slow drying. Leave undisturbed for at least 24 hours.
Flip the mould upside down and lay it flat. Ease the corners and sides of the mould away from the paver. Apply gentle pressure to the top corners and the centre of the mould while lifting the sides to release the stone. Clean the mould with water and a stiff-bristle scrub brush. Dry and apply mould release in preparation for the next casting.
Lay the stones out in rows under cover. A chemical reaction will take place during the curing process. The slowest drying rate possible will ensure optimum curing and the strongest patio stone or paver. Spray the stones liberally with a hose. Spread plastic sheeting or a waterproof tarpaulin over the stones, and weigh the corners down with bricks or stones.
Repeat the watering process every two or three days. The bare minimum curing period for non-load-bearing tiles or veneer is 24 hours after de-moulding. The chemical reaction necessary for optimum strength required for patio stones, stepping stones or pavers will take 30 to 45 days.
Although using old engine oil or diesel works as a releasing agent, it is not recommended for ecological reasons. If you are purchasing a releasing agent for a larger project, use an eco-friendly water-based product. If you have a small project, light vegetable oil is an alternative to using commercially available releasing agents. If you have a large project, purchasing or making your own vibrating table to compact the wet concrete may be worthwhile.