As a construction expert with a focus on materials and structural integrity, I can provide a detailed answer to your question about putting concrete on top of existing concrete. This process is commonly referred to as an "overlay" and is a practice that can be used for various purposes such as leveling uneven surfaces, providing additional structural support, or simply to improve the aesthetics of a concrete slab.

Step 1: Assessing the Existing Slab
Before you can proceed with pouring a new layer of concrete, it's crucial to assess the condition of the existing slab. Look for any signs of damage such as cracks, spalling, or unevenness. If there are significant structural issues, it may be necessary to repair or reinforce the slab before adding a new layer.

Step 2: Preparing the Surface
The surface of the existing slab must be properly prepared to ensure a strong bond between the old and new layers of concrete. This typically involves cleaning the surface to remove any dirt, grease, or other contaminants. It may also be necessary to roughen the surface by grinding or sandblasting to increase the surface area for better adhesion.

Step 3: Considerations for the Overlay
When deciding on the type of material for the overlay, you must consider the added height and weight that the new layer will impose on the existing structure. Polymers, Portland cement concrete, and epoxies are all viable options, each with their own set of benefits and considerations. Polymers are lightweight and can provide good flexibility, while Portland cement is more traditional and may be more suitable for heavy loads. Epoxies are very strong and durable but can be more expensive.

Step 4: Mixing and Pouring the Overlay
The process of mixing and pouring the overlay is similar to that of a regular concrete pour, but with a few additional considerations. The mix must be designed to bond well with the existing slab and to support the additional load. It's also important to pour the overlay in a way that minimizes air pockets and ensures an even distribution of the material.

Step 5: Curing the New Layer
After the overlay has been poured, it's essential to cure it properly to achieve maximum strength and durability. This typically involves keeping the surface moist for a period of time, which can be done through methods such as wet curing or using curing compounds.

Step 6: Maintenance and Monitoring
Once the overlay has cured, it's important to monitor the new layer for any signs of distress or failure. Regular maintenance, such as sealing and resurfacing when necessary, can help to prolong the life of the overlay and the overall structure.

In conclusion, while it is possible to put concrete on top of existing concrete, it requires careful planning, preparation, and execution to ensure the success of the overlay. It's always recommended to consult with a structural engineer or a professional contractor to assess the specific needs and conditions of your project.

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New Slab on Top of Old. ... Yes, you may pour a concrete pad overlay over an existing slab. You need to consider the added height and weight of the overlay on the existing structure. Overlays may include polymers, portland cement concrete, or epoxies.Dec 15, 2001read more >>