Damage Evaluation of the Paving around Manholes under Vehicle Dynamic Load

It is very important for pavement engineers to know which factors are the main reasons for the damage of the paving around manholes. Based on the investigation on the damage of paving around manholes, a vibration model with multidegree of freedom for the vehicle-manhole cover was established and analyzed. After that, the Matlab software was used to obtain the variation law of impact load over time, and the 95% fourth power of the aggregate force was used as the index to evaluate the pavement damage. Finally, many influencing factors on pavement damage were analyzed by the method of grey correlation entropy. The results indicated that the impact load reached the maximum for the first time when the vehicle reached the top of the manhole cover, which was 1.29 times that of the static load, and the pavement damage coefficient was 2.12 times that of the static load. The influencing factors had different degrees of influence on the pavement damage; from large to small, they were change of road longitudinal slope > driving speed > damping of tire > stiffness of tire > height difference from the pavement damage > height difference from the manhole settlement > stiffness of the manhole cover

Experimental Investigation on Physical Properties of Concrete Containing Polypropylene Fiber and Water-Borne Epoxy for Pavement

Cement concrete pavement accounts for a large proportion of the road network due to its excellent mechanical strength and durability. However, numerous microcracks are generated due to the high brittleness of concrete, which poses a threat to the service life of concrete pavement. Currently, simultaneous addition of fibers and polymers is a feasible approach to resolving the issues associated with the brittleness of concrete. This study explores the properties of concrete mixtures containing different levels of polypropylene fibers and water-borne epoxy. Additionally, fly ash is also introduced to concrete mixtures. The tests performed include slump, compressive strength, flexural strength, shrinkage, depth of water penetration, and abrasion. The results indicate that water-borne epoxy, at all levels, contributed to improving the weak interfacial bonding between polypropylene fibers and concrete. In addition, the combined incorporation of polypropylene fibers and water-borne epoxy could improve the mechanical and durability properties of concrete, with the combined utilization of 0.1% polypropylene fibers and 10% water-borne epoxy exhibiting the best performance. Moreover, with the incorporation of 10% fly ash into concrete, the mechanical strength and abrasion resistance experienced a slight reduction, while the workability, drying shrinkage resistance, and impermeability were improved. The current findings indicate that the combined utilization of polypropylene fibers and water-borne epoxy at appropriate levels is beneficial for application in pavement; however, in spite of superior drying shrinkage resistance and impermeability, the incorporation of fly ash into concrete pavement should be properly treated according to the actual engineering conditions

Properties of SBS/MCF-Modified Asphalts Mixtures Used for Ultra-Thin Overlays

In order to produce high-viscosity and high-toughness asphalt for ultra-thin overlays, the conventional asphalt cement was modified with high-content SBS and micro carbon fiber (MCF). The performances of the modified asphalt were studied by tests of penetration, softening point, ductility, kinematic viscosity, multiple stress creep recovery (MSCR), and by dynamic shear rheometer (DSR) and bending beam rheometer (BBR). Mixture properties were studied by tests of rutting, low-temperature bending, freeze–thaw splitting, four-point bending fatigue and dynamic modulus. The results reflect that the addition of MCF could enormously improve the high- and low-temperature properties, increase the viscosity of asphalt, and improve the toughness of asphalt. When SBS content was 6%, with the increase of MCF content, G*/sin δ and R values first increased and then decreased, and the Jnr value first decreased and then increased. When MCF content was 0.8%, the overall performance was best. Adding MCF into an asphalt mixture or increasing the content of SBS improved the rutting resistance, low-temperature crack resistance, water stability, and fatigue performance of the asphalt mixture. At the same temperature and frequency, there was little difference in phase angle between the 6%SBS + 0.8%MCF and 5%SBS + 0.0%MCF modified asphalt mixtures, and the dynamic modulus was slightly higher over the whole range. It can be concluded that the addition of SBS and MCF can enormously enhance the viscosity and toughness of asphalt. The viscosity of the 6%SBS + 0.8%MCF modified asphalt met the performance requirements of high-viscosity asphalt. When used for ultra-thin overlays, it had great road service performance and met the application requirements