This app is designed to encourage a better understanding of the use of thin-polymer overlay (TPO) systems for the preservation of concrete bridge decks. A TPO refers to a multi-layer overlay system that includes a polymer resin binder with polish-resistant aggregates broadcasted or seeded into the wet polymer prior to gelling or curing. The aggregate acts to provide friction for the wearing surface. This is typically applied in two layers at a specified coverage rate. A primer or pre-treatment is sometimes used to seal cracks and act as an adhesion promoter for the TPO. The TPO system is typically 3/8 inches in thickness when properly installed. Thickness may vary slightly dependent upon the gradation of broadcast aggregates specified for the project. A TPO is designed to: Minimize the intrusion of moisture, de-icing chemicals, carbonation, and other potential sources of the pre-mature degradation of concrete bridge decks. Provide a protective, durable, skid-resistant wearing course for a concrete bridge deck. This app is intended to educate the designer, owner, contractor, and inspectors about TPO installation best practices. By acting with a better understanding of their designed intent, the bridge owner can capitalize on the potential benefits of these overlay systems. Although some broad guidance is suggested as to bridge deck condition assessment, this subject is not the primary intention of this app. The same holds true with the selection of TPO materials.