Concrete Joints are one of the main areas where concrete starts breaking down. This is due to extreme pressures that the concrete slabs undergo during the weight transfer of heavy loads and vehicular traffic. Joints are essential in concrete as it allows slabs to move naturally so as to not crack under the weight. Usually at these joints (within the concrete) are metal support bars linking the slabs so that they don't rise or drop throughout their lifespan. You also find saw cuts in the concrete as this induces the natural cracking that occurs and helps reduce it going in any direction it desires (like a spiders web) leaving neat straight lines through the floor. Joints should be sealed, normally with a mastic sealant (different varieties are available for different applications e.g. fuel and chemical resistant) as this helps support the joint edge under traffic and stops water penetration that could damage the concrete from within. With R&J, you have peace of mind knowing that any repairs undertaken are done so that they resolve the issue entirely leaving you to focus on your normal day to day business.