We have varying or mottle color areas on the surface of our smooth, new concrete floor. We do not like this appearance. How did it happen? What can we do about it? Also, who should we blame?
Your question is asked often. The causes I know about are differing cement sources used in the same floor or concrete pour. Wide variation in the water content of the concrete mix delivered to the project. More water, lighter color, less water, darker color from the same cement. Nonuniform doses of calcium chloride accelerator, leaving a dark spot.
Cheating in the finishing operation by "hot shot" dusting the surface with dry cement powder. Nonuniform finishing, or final troweling efforts. Lastly, splattered or poorly applied curing compound or sheet goods. Resulting in dark and light shades or streaks imitating the folds in the sheet goods.
I do not know exactly who to blame, the onsite inspector is saddled with that question to answer.
I do have ideas on how to minimize some of the color variations. Avoid changes in cement sources for the concrete. Require a constant or continuous placement and finishing protocol on each days pour. Insist on a uniform slump or water content in the concrete coming to your project. Apply the curing products or systems in a uniform manner and pull out wrinkles in the sheet goods.
In closing, the rock and sand have a color contribution to the concrete, examine this situation, too. Your area may be stuck with a local supply of rock and sand with a color potential.
Once all the above steps to minimize color variation have been observed, use L&M's E-CON as the professional finishers' choice for the best finish on concrete surfaces.