Concrete is a strong and low-maintenance material that is often used for decorative purposes or to repair damage. You can pour a new, thin slab of concrete over an existing walkway, patio, or porch as long as it is no less than 1.5 inches thick and contains wire mesh or fiber reinforcement. To ensure the best results, you should pressure wash the old concrete to remove any mold, dirt, and loose concrete before pouring the new layer. When pouring the new concrete, you should use a type of reinforcement such as fiber mesh or reinforcing bar to help control and prevent any cracks that may develop as the concrete sets.
Fine sand or crushed stone is preferred for small-thickness concrete and coarse-grained aggregate is used for thicker concrete. Maintaining your concrete steps by sweeping and hosing them regularly can help extend their useful life and prevent imperfections from forming. Pouring a new layer of concrete over an existing slab can raise the level by several centimeters and save you hundreds of dollars compared to having to do a demo and remove the old concrete. If you're trying to freshen up a tired looking patio, you can cover small cracks and damage with a new layer of concrete.
However, if the thickness is less than 3 inches, you need to use a bonding agent to bond new concrete to old concrete.