In the last several years, MoDOT has experienced problems with excessive amounts of cracking on some new concrete bridge decks. This has led to various concrete sealers being used for sealing cracks as well as whole decks, instead of applying linseed oil. Linseed oil is the only concrete sealer listed in Missouri's Standard Specifications, and is used for resistance to scaling on new bridge decks. Secondly, some recent projects re-texturing decks built with dense concrete overlays have specified penetrating concrete sealers. The concern was if linseed oil was used on the diamond ground surface, it might not have good frictional properties. Either extra linseed oil might be left on the surface or the linseed oil might not cure quickly enough to switch traffic onto it after short lane closures. It was decided that new penetrating sealers be used in these situations by special provision to the contract. Four types of penetrating sealers were tested against linseed oil in the laboratory to rate their effectiveness, pick criteria for testing needed in accepting sealers and write a new specification to best protect concrete bridge decks from deterioration. In the case of new concrete decks it is recognized by American Concrete Institute that cracks smaller than 0.18 mm do not let chloride ions from salt penetrate through them. It was concluded that if there are very few cracks bigger than this, those cracks do not need to be sealed, and linseed oil can be used to help prevent scaling. If cracks were bigger than this it would be better to forego the linseed oil treatment and use a crack sealer. A table with concrete sealers classified into three performance groups is presented with the sealers ranked by performance and including cost per ft. 2. It was found from this study that penetrating sealers are not good at sealing large cracks. Although an Ohio DOT test was used in this study to measure crack sealing capabilities, it did not give consistent answers. It did help identify what size cracks need to be sealed by a better crack sealer, such as a two-part epoxy. It was found that cracks in the range of 0.30 mm to 0.64 mm start to allow a saline solution to leak through the concrete very swiftly. So even if a penetrating sealer is used on a deck with many cracks, those 0.64 mm cracks and bigger need a more appropriate crack filler/sealer to seal the individual big cracks first. Sealing cracks on existing older decks should be done using less expensive products that seal the entire small and medium-sized cracks and are effective for 2-4 years. A table listing these crack sealers is also presented. As a result of testing in this study one of these products was approved for preventive maintenance use statewide.