Concrete is a porous substance, and when water seeps through the floor it can damage equipment stored in the garage or shop space. In a commercial space such as a grocery store, concrete floors must be waterproof for safety reasons. You can stop moisture from coming up through a garage floor with the right tools.
Clean your garage floor by scrubbing it. Clean it free of dirt, oil and any previous sealer that was used. Use a power scrubber and a degreaser detergent.
Floor grinders are helpful, but if you don't have access to one you can try a muriatic acid bath. Mix four parts water and one part muriatic acid. Follow this treatment with an ammonia solution, using one part ammonia mixed with 10 parts water. This will neutralise the floor and prevent deterioration. When applying the acid, always use a respirator to protect your lungs.
Fill any cracks in the concrete floor. Seal large cracks by filling them with sand topped by an epoxy sealer. Seal small cracks with an epoxy or concrete sealer. Once the epoxy is applied and allowed to harden, sand the top down until it's flush with the concrete. Do not seal tooled joints, as they are designed to be there. You can fill the joint with a small amount of latex caulk for waterproofing.
Test for moisture to see if you have water vapour seeping through. Tape a piece of plastic sheeting to the floor on all sides. Leave it for one to two days, then pull it up. If there is condensation on the underside of the plastic you'll need to seal the floor for water vapour. Exterior tar waterproofing provides a water vapour barrier.
Apply a surface coating after implementing the water vapour barrier. Consider the appropriate garage floor coating that suits your specific needs. Some are extremely durable against abrasions, while others can better withstand heat. Latex paints, epoxies, masonry stains and polyurethane based floor coatings are also acceptable.