Grinding And Polishing Concrete
The Mix, Pour And Finish
Polished concrete is strong, durable and low maintenance and comparable to traditional polished terrazzo. Both can either be ground flat to fully expose the aggregate, the aggregate can be partially exposed or lightly ground to expose no more than the fine sands at the surface (salt and pepper).
Where the aggregate is the main feature special supplies can be added to the wet mix such as coloured pebbles, metals and glass to enhance the appearance. Select your sand, cement and aggregate and ensure there is enough for the project. It is advisable to do a test panel.
The mix and trowelling of the concrete is important. You cannot turn poorly batched and mixed concrete into a uniform stone like finish (pig’s ear into a silk purse). Concrete that has been mixed in a free fall cement mixer will not be uniform; there will be soft and hard areas also patchy areas of aggregate. The concrete should be mixed in a forced action mixer with consistent batching of the materials to give the concrete a uniform finish when ground and polished. Soft and hard floors also produce different results when ground.
The wet concrete should flattened with a long handle bull float and then be power floated to get a uniform finish and bring the fat and fine sand to the surface. The floor should be as flat as possible at the application stage as it is far more time consuming to rectify any unevenness later. If the wet concrete has been walked over, boot marks can appear during grinding because they have depressed the aggregate If the surface is to be polished without exposing the aggregate, then only the finer grit diamonds need to be used. This will result in a polished floor without showing the pattern and texture of the exposed aggregates within the concrete which is quicker and less expensive.