With the overnight growth in exposed concrete floors in grocery and retail stores, schools, collages, museums, government buildings, private homes and so on, all require joint fillers for housekeeping and protection. Unfortunately, polyurea joint fillers currently being used today all have similar problems.
Typical problems associated with today’s joint fillers are separation from the concrete edge, splitting of the filler itself, and discoloration. The reason for this can be contributed to the fact they are or aromatic polyureas.
The good news is that developments in “aliphatic” polyurea technology now offer a better alternative when specifying joint fill materials. The positive attributes associated with aliphatic overcome traditional downfalls of aromatic polyurea evidenced in many installations throughout decorative concrete floors.
Aromatics by nature are not UV stable either from sunlight or indoor lighting. All aromatics will change color, despite saying they are UV resistant. The color change can be overnight or gradually over time. Additionally, aromatics have limited elongation capability to compensate for joint width change. Products can be made softer to increase elongation. However, the problem with softer fillers is they are more susceptible to damage and do not support the joint edge as well as harder fillers do. ACI and PCA both recommend a hardness of Shore A80 for this very reason.
Today’s aromatic polyureas are extremely fast setting. High viscosity liquids that are fast setting do not wet-out the side walls of the joint enough to achieve a sufficient bond strength. Most polyurea joint fillers have a gel time of less than 1 minute, and some less than 30 seconds! The tack free time is under 5 minutes. With such fast-setting fillers, it’s understandable why there is isn’t enough wet-out time and to achieve the adhesion needed to keep the filler attached inside the joint. If there is not good adhesion, then lowering the filler’s hardness to increase elongation has minimum benefit and actually is likely to create additional problems later on. Primers are used to promote adhesion in sprayed polyurea applications, such as coating a parking structure, a seawall, or a lining a tank. However, priming the inside surface of concrete joints is impractical, so it is not typically done.
By switching specifications to an aliphatic polyurea, traditional problems associated with aromatics are overcome.
The new aliphatics are UV stable under both sunlight and all types of indoor lighting. Any color selection, even white will always remain as true as the day it was installed.
Aliphatic polyureas have significantly better elongation - more than twice that of most aromatic polyureas with equal hardness such as Shore A80. This eliminates the need to use a softer filler that will provide much less joint protection to attain higher elongation capability.
Aliphatic polyureas are slower than aromatics. The gel time is 15 to 20 minutes with the tack-free time around 45 minutes. This slower setting filler greatly increases the wet-out time on the inside walls of the joint, providing exceptional improvement of adhesion and bond strength.
The significant advantages of using aliphatic polyurea over aromatics are well worth considering when specifying joint fillers for decorative concrete floors. To find out more about the advances in aliphatic polyurea technology visit EZ Pour on the Products Page of this website