How To Finish Cement Patio Slabs On Concrete

Pouring a cement patio slab over an existing concrete surface offers a cost-effective way to revitalize outdoor spaces. This process, however, requires careful preparation and execution to ensure a durable and aesthetically pleasing result. This article outlines the necessary steps to successfully finish cement patio slabs on concrete.

Assessment and Preparation: Begin by thoroughly assessing the existing concrete surface. Look for cracks, spalling, or any signs of deterioration. These issues must be addressed before proceeding. Clean the concrete surface using a pressure washer to remove dirt, debris, and any loose concrete. This cleaning process is crucial for proper adhesion of the new cement layer.

Repairing Existing Concrete: Cracks and damaged areas require repair before pouring the new slab. Use a concrete patching compound specifically designed for exterior applications. Follow the manufacturer's instructions for proper mixing and application. Allow the patched areas to cure completely according to the manufacturer's recommendations.

Applying a Bonding Agent: A bonding agent, or bonding primer, is essential for creating a strong bond between the existing concrete and the new cement overlay. Apply the bonding agent evenly across the entire surface using a roller or brush, following the manufacturer's instructions. Allow the bonding agent to dry according to the recommended timeframe before proceeding.

Formwork Installation: Install formwork around the perimeter of the area where the new slab will be poured. Ensure the formwork is level and securely braced to prevent movement during the pouring process. The formwork should be constructed from sturdy materials such as 2x4 lumber and should be adequately staked to maintain its position.

Mixing the Cement: The cement mixture should be prepared according to the manufacturer's specifications. Use a concrete mixer for larger projects to ensure a consistent mix. For smaller projects, hand mixing in a wheelbarrow is acceptable. Maintain the proper water-to-cement ratio to achieve the desired consistency and strength. Adding too much water will weaken the concrete, while too little will make it difficult to work with.

Pouring the Cement: Pour the cement mixture into the formwork, starting at one corner and working systematically across the area. Use a shovel or rake to spread the cement evenly. The depth of the new slab should be consistent throughout. Aim for a minimum thickness of 2 inches for adequate strength and durability.

Screeding and Leveling: After pouring, use a screed board to level the surface of the cement. Place the screed board on the formwork and move it back and forth across the surface, removing excess cement and creating a level plane. For larger areas, a bull float can be used to further smooth the surface and remove any imperfections.

Floating the Concrete: Once the bleed water has evaporated from the surface, use a hand float or power trowel to further refine the surface texture. Floating helps to consolidate the cement and create a smoother finish. This step is crucial for achieving a professional-looking result. Multiple passes with the float may be necessary to achieve the desired smoothness.

Edging and Grooving: Use an edging tool to create rounded edges along the perimeter of the slab. This not only enhances the appearance but also protects the edges from chipping. Grooving, or creating control joints, is essential for preventing cracking due to expansion and contraction. Use a grooving tool to create shallow grooves at intervals specified by the concrete mix manufacturer or according to standard practices.

Curing the Concrete: The curing process is critical for achieving the desired strength and durability of the concrete. Keep the concrete surface moist for at least 7 days after pouring. This can be accomplished by covering the slab with plastic sheeting or by regularly misting the surface with water. Proper curing allows the concrete to hydrate fully and develop its maximum strength. Avoid heavy traffic or placing objects on the newly poured slab during the curing period.

Sealing the Concrete (Optional): Once the concrete has fully cured, applying a concrete sealer is recommended. A sealer provides protection against staining, moisture penetration, and weathering. Choose a sealer appropriate for exterior applications and follow the manufacturer's instructions for application.

Post-Curing Care: Regular cleaning and maintenance will prolong the life of your concrete patio. Sweep the surface regularly to remove dirt and debris. Periodically clean the patio with a mild detergent and water. Avoid using harsh chemicals or abrasive cleaners that can damage the concrete surface.