8.9 : Finishing Concrete

Concrete finishing starts immediately after the concrete has been placed and consolidated. The initial step, screeding, involves leveling the concrete surface by removing excess material to flush it with the formwork's top. Following this, bull float or darby are employed to smooth the surface further, effectively lower high spots, fill low areas, and ensure larger aggregate particles are embedded within the concrete. This preparation is critical before the appearance of bleed water, as its presence can lead to scaling and dusting.

Once the surface is free from bleed water, the concrete is ready for its final finishing. This involves edging, which rounds off the slab's edges to prevent chipping; jointing, the creation of control, isolation, and construction joints to manage the concrete's natural movements and prevent unsightly cracking; and floating. The latter smooths out any imperfections left by the previous steps, slightly embeds the aggregate below the surface, and compacts the mortar at the surface for final finishing while allowing excess moisture to escape.

Concrete's final appearance and texture are achieved through various techniques, such as troweling to smooth and harden the surface, and brooming to roughen the surface. Additionally, patterns or exposed aggregate finishes can be applied to create decorative effects.