After the initial operations of spreading, screeding and darbying, concrete should be allowed time to begin its setting process. When there is no bleed water or excess moisture on the surface and the concrete will sustain foot pressure with only about 1/4-inch indentation, the next finishing operations should be performed. This article outlines the steps that should be followed for: light-duty plain finishes, heavy-duty wear-resistant finishes, hard surfaces by means of dry shakes, natural-aggregate dry-shake procedure, nonslip wear-resistant surfaces, finishing of air-entrained concrete, and finishing of structural lightweight concrete.
HEAVY-DUTY WEAR-RESISTANT FINISHES
This category includes industrial floors, warehouse floors and loading docks. The operations of spreading, screeding, darbying or bull-floating, floating and troweling are the same as for any ordinary concrete slab. However, the concrete should be of high quality. It should have a minimum cement content of 565 pounds per cubic yard, a design strength of at least 4500 psi, and be placed at a slump of not more than 3 inches. A minimum of three trowelings by hand or four by machine should be performed. Additional trowelings, which produce a harder more wear-resistant surface, will also produce a surface that is less absorptive of harmful liquids.