Concrete control joints are a necessary part of a stable, durable slab, allowing individual sections of the concrete to contract while curing or shifting and moving over time without cracking or causing damage to adjacent pieces. Learn how to properly clean, repair, and fill a concrete joint in our step-by-step guide, and be sure to watch the video below to see how our team completes the task.

Preparing the Concrete Joint

The first step is to use a floor grinder to grind the concrete to remove any excess mortar and then begin cleaning out the joint using the 5″ Hand-Held Premium Crack Chaser from U.S. Saws, a 110V shrouded crack/joint saw. This is a handheld machine that features a rotating dry diamond blade that goes down into the joint, cutting through mortar and cleaning out the void down to 1.25″ deep. A dust collector is attached to the saw to remove debris and dust and clean out any dust from the void.

As you see in the video, this is not a single-pass task. Instead, you’ll need to run the Crack Chaser multiple times through the joint to get rid of the old mortar. We then run a small shot blaster over the joint to clean the concrete around it and remove old dust and debris.

Filling the Joint

After shot blasting the joints, it’s time to refill them using Smith’s PolyJF (for joint filler). Thoroughly mix the joint filler using the manufacturer’s direction, then pour some of what you have into a smaller container for increased control and precision.

Pour the compound filler directly into the joint, slowly, taking care to not overflow too much and allowing time for the filler to sink all the way into the void and ensure the compound reaches the top. Smith’s PolyJF is a polyurethane filler that is ideal for this task as it’s durable and ensures tenacious adhesion in both joints and cracks.

Finishing the Concrete Joint

After waiting 18 hours for the PolyJF to completely dry and cure, you can start finishing the slab. We recommend using a concrete grinder to go over the joints until the joint is even with the concrete slab. During this process, be sure to use a dust collector for safety as well as easier cleanup. Once it’s complete, run over the area with a microfiber mop to get any extra dust and move on to preparing the slab for coating, if needed.

Order Your Surface Preparation Materials Today

Whether you need a concrete grinder, shot blaster, or simply joint compound, we have everything you need to do your next project right. To learn more or to get a quote on materials, call us at  (815) 472-9749 to speak with an expert today!