Hydrolysis: urethane’s weakness

We tout our urethane concrete mixer drum liners as often outlasting steel, especially when it comes to sliding abrasion. But urethane does have one weakness: standing water.

When water is left in a mixer drum lined with urethane, the humidity that occurs causes a chemical breakdown of the urethane called hydrolysis. This breakdown is evident when the liner starts chipping and crumbling and eventually peels away from the embedded weldplates and falls out.

Hydrolysis occurs faster the hotter the temperatures are, so as we approach spring and summer it’s important to keep these tips in mind:

• Hydrolytic attack will typically only occur if hot water is allowed to sit in the drum for weeks, months or even years.

Concrete drums are almost always hot and humid, especially when fresh concrete is being produced within them. However, this heat and humidity will not cause hydrolysis of the liner when the drum is in use frequently. It is thought that the lime in the cement acts as a neutralizer to help prevent acid buildup.

• When the central mix drum is being used on a regular basis the drum can just be washed out as normal and some small amounts of rinse water can be left in the drum.

If, however, the drum is to be left without use for an extended period of time, all water should be emptied from the drum and it should be positioned to allow for drainage. It should then be protected from the rain or other water sources while out of service. The drum should not be totally sealed, though, as airflow will allow any remaining water to evaporate.

• Don’t worry, though, we have a solution! If used in areas of hot weather, humidity and long periods of inactivity, such as the south, Argonics ether liners have proven superior against hydrolytic attack.

Ether has a slightly different chemical makeup compared to the standard ester liners and is substantially more resistant to hydrolysis.

Proper care and maintenance of the urethane liner, including repairing gouges and tears, maintaining seams, and inspection on a regular basis, should also include removing all water from the drum. Following these guidelines will ensure that the liner continues to perform for a very long time.