Mechanisms of Blister Formation on Concrete Bridge Decks with Waterprooving Asphalt Pavement Systems

Sammanfattning: Bridge decks are commonly subjected to harsh environmental conditions that often lead to serious corrosion problems triggered by blisters under the hot mix asphalt bridge deck surfacing and secretly evolving during weather exposure until damage is often detected too late. Blisters may form under both the waterproofing dense mastic asphalt layer or under the waterproofing membrane which is often applied as additional water protection under the mastic asphalt (MA). One of the main technical issues is the formation of blisters under the membrane and asphalt-covered concrete structures caused by a complex mechanism governed by bottom-up pressure and loss of adhesion.A linear viscoelastic finite-element model was developed to simulate time-dependent blister growth in a dense mastic asphalt layer under uniformly applied pressure with and without temperature and pressure fluctuation. A finite element model was developed using ABAQUS with linear viscoelastic properties and validated with a closed form solution from first-order shear-deformation theory for thick plates. In addition, the blister test was conducted on different samples of MA in the laboratory and digital image correlation measurement technique was used to capture the three-dimensional vertical deflection of the MA over time. It was found that the blister may grow continuously under repeated loading conditions over subsequent days.With respect to blistering under waterproofing membranes, mechanical elastic modeling and experimental investigations were performed for three different types of membranes under in-plane stress state. The orthotropic mechanical behavior of a polymer modified bitumen membrane (PBM) was determined from biaxial test data. Finally, blister tests by applying controlled pressure between orthotropic PBMs and concrete plates were performed for studying the elliptical adhesive blister propagation using digital 3D image correlation. The energy calculated from elliptical blister propagation was found comparable to the adhesive fracture energy from standard peeling tests for similar types of PBMs. This indicates that the peeling test assists to evaluate and rank the adhesive properties of different types of membranes with respect to blister formation at room temperature without conducting time consuming and complicated pressurized blister propagation tests using digital 3D image correlation.