Experimental study of the performance of a stress-absorbing waterproof layer for use in asphalt pavements on bridge decks

Abstract The presence of negative bending moments at the top of a continuous beam bridge can facilitate the sawing of false seams. The concrete bridge deck and its asphalt pavement will therefore develop transverse fatigue cracks under long-term cyclic traffic loads. This paper aims at preventing reflective cracks from forming in such asphalt pavements. The structure and materials used in crack prevention based on a composite stress-absorbing layer (CSAL) consisting of a geotextile and an asphalt gravel seal coat were investigated. The properties of polypropylene (PP) geotextiles were evaluated by means of differential scanning calorimetry, thermogravimetric analysis, thermal shock tests, etc. Adhesion, shear, and tensile tests were used to study the influences of factors such as the type, amount of asphalt materials, and construction temperature on the bonding performance of the pavement interface. Texas overlay tests were also carried out to explore the anti-reflective cracking and anti-fatigue performance of different pavement structures including an asphalt rubber stress-absorbing membrane interlayer (ARSAMI) and a CSAL. The results show that the PP geotextile has a melting point of about 166 ℃, a glass-transition temperature in the range of –20 to –10 ℃, and a thermal decomposition temperature of about 400 ℃. In addition, it retains good strength and deformability when subjected to thermal shock at 180 ℃, and it has high thermal stability. The modified asphalt has the highest adhesion strength to concrete slabs, followed by ordinary asphalt and then emulsified asphalt. The temperature state of the bonding layer is not sensitive to the bond strength of the bridge deck paving structure. The asphalt mixture waterproofs the surface after paving. The adhesive stress-absorbing layer imparts a secondary heating effect, thereby ensuring interface adhesion. Using a pavement structure with a CSAL can enhance resistance to reflective cracking at a low temperature by more than 5 times compared to the case not taking preventative measures. Its resistance to reflective cracking under a deformation amplitude of 2 mm at the room temperature (20 ℃) is also slightly better than that of the ARSAMI. Hence, CSALs have promising prospects for use in crack prevention.