Bridges are a vital component of transportation infrastructure in the United States, and the continual maintenance and preservation of bridges is critical to maintaining their structural capacity and maximizing service life. One of the most significant issues faced by concrete bridges is the infiltration of moisture from the roadway surface into the concrete bridge deck. When moisture penetrates into the deck, the expansion and contraction of the moisture during freeze-thaw cycles can increase the rate of deck deterioration. Additionally, penetrated moisture can carry with it chloride ions from deicing salts and roadway pollutants. These chloride ions can react with the steel reinforcement within the deck and cause corrosion, which in turn will lead to areas of localized expansion. When the corrosion around steel forms, it creates an internal volume change (expansion) and results in cracks in the surrounding rigid concrete which may propagate to the surface of the bridge deck, weakening the structural integrity of the bridge.
One of the most common methods of preventing moisture infiltration into a concrete bridge deck is through the use of waterproofing membranes which are constructed on top of the concrete deck. There are two main types of membranes- liquid membranes and pre-formed membranes. Liquid membranes are typically either sprayed or poured directly onto the concrete deck and create a very strong bond between the membrane and the concrete. These types of membranes, however, are often costly and time-consuming to install. Pre-formed membranes come in premade sheets which are typically rolled out onto the concrete bridge deck. The placement of preformed membranes is extremely easy and inexpensive, however these membranes create a much weaker bond with the underlying concrete deck. For all membranes, an asphalt wearing course is paved over the top to prevent damage to the membrane from vehicular loads.
Some states have been looking into alternative strategies to protect and seal concrete bridge decks. One alternative strategy is the use of a high-density impermeable asphalt layer constructed directly on a deck in place of a waterproofing membrane. This method is advantageous because it can be constructed using traditional paving methods and unlike waterproofing membranes, it does not require a specialty subcontractor to install.
The use of membranes and overlays to protect an underlying structure is not a practice exclusive to bridges. The Glenwood Cross-Laminated Timber (CLT) Parking Garage is one structure which seeks to push the boundaries regarding what is possible using CLT as the primary building material, is set to be constructed in Springfield, Oregon, and would be the first CLT parking garage in the United States. To avoid damaging the CLT floor panels in the garage, a surfacing overlay will need to be constructed to accommodate the vehicular traffic, provide skid resistance and waterproofing, and minimize stresses to the CLT members.
This thesis is presented in a manuscript format. Chapters 2 and 3 focus on the evaluation of several existing waterproofing membrane strategies as well as the development of an impermeable asphalt mixture for protecting concrete bridge decks. Laboratory test results showed that pre-formed rolled waterproofing membranes perform worse than liquid membranes with regards to both bond strength and permeability tests. A high-density impermeable asphalt mixture was designed in the laboratory which was both impermeable and was found to have strong cracking and rutting resistance. Chapter 4 seeks to identify the most effective surfacing overlay for the Glenwood CLT Parking Garage. Finite Element modeling and laboratory testing of CLT surfacing strategies determined that the presence of an asphalt overlay greatly reduces the strains from vehicle loadings being transmitted to the CLT floor panels.