Nothing could be worse than successfully pouring a concrete slab, only to find that the surface of the concrete is mottled by discolorations once dry. Unfortunately, depending on the particular curing method used, this problem is relatively common. If you would like to learn more about why wet concrete becomes discolored--and how to stop it--read on. This article will answer three common questions about this frustrating phenomenon.
Why do concrete discolorations occur?
Discolored patches of concrete most commonly occur when plastic sheeting has been used as the curing membrane. In this curing method, a thin polyethylene sheet is placed flush against the surface of the concrete to prevent water from evaporating as the concrete hardens. Problems develop when the sheet is not in complete contact with all portions of the slab.
Wrinkles or bubbles in the sheeting lead to discoloration by what is sometimes referred to by the name of the greenhouse effect. This refers to the tendency of water to evaporate and then condense inside of the wrinkled area. This water then runs back down onto the concrete, thus altering the curing conditions in those areas, and leading to the formation of discolored patches.
How can this problem be avoided?
If plastic sheeting remains the preferred curing method, discolorations can be avoided by taking care in ensuring that no bubbles or wrinkles occur when unrolling the polyethylene. Those who are flexible as to their curing method may avoid the greenhouse effect by utilizing a so-called liquid membrane curing compound instead of plastic sheeting.
A liquid membrane curing compound is sprayed onto the surface of the concrete immediately after the last round of troweling has occurred. So long as it is evenly covering the entire slab, the chemical composition of the liquid membrane provides a water-tight protective barrier, on that is capable of retaining no less than 95% of the concrete's moisture content.
Are there other factors to be worried about?
Though wrinkled plastic sheeting is by far the most common cause of discoloration, there are other factors that may affect the final concrete appearance. The alkali content of a particular cement plays a role in the ultimate shade of the concrete, thanks to the formation of substances such as alkali chlorides and carbonates.
This often leads to slight color differences when contiguous sections of concrete flooring are created using different batches of concrete. When only one batch of concrete is to be used, discolorations can be successfully avoided by ensuring that the concrete is consistently mixed before being poured. Talk to a contractor, like Stephens & Smith Construction Inc, for more help.
My name is Marcus Thompson and about 8 years ago I found myself raising 3 children on my own. Before becoming a single father, I was too busy in my corporate world to even realize my home was falling apart. However, as I began spending more time at home, I began to notice all of the issues that were quickly causing my home's value to decrease. I couldn't afford to hire a contractor to fix these issues, so little by little, I began learning how to fix these problems myself. Over the years, I became a dedicated DIY enthusiast who is capable of fixing any issue I may encounter in my home. Creating this website is my way of sharing everything I have learned over the years with other parents and homeowners so that they too can begin taking control of any issues they may experience with their home.