Advances and development trends in eco-friendly pavements

The major contemporary in road pavement engineering is related to the creation of green and sustainable infrastructures,e.g.,reduction of environmental impacts,increase in traffic safety,and transportation efficiency,etc.This review presents the recent trends in research and the technical solutions developed so far to address these challenges.After the analysis of research status in the past decades,a novel technology system of eco-friendly pavements is proposed considering two solutions,materials modification and structure improvement.The construction of an eco-friendly pavement can be achieved thanks to several different technologies ensuring permeable,noise-reducing,self-luminous,and exhaust-decomposing properties as well as apporting lower heat absorbing and enhanced anti-/de-icing characteristics.A systematic review of these technologies is presented pivoting on four main aspects:technical principle,material and structural composition,performance evaluation,and engineering application.The current trend in road engineering is combining the pavement infrastructure with various eco-friendly functions,e.g.,water permeability,noise reduction,low heat absorption,exhaust gas decomposition,and anti-/de-icing.Finally,the review lists the drawbacks of the existing technologies,including high cost,single function,etc.,and depicts the future developing direction and architecture of the next generation of eco-friendly pavements in which the road infrastructure should have more environmentally friendly functions than the existing technology.

Effect of Encapsulation Combined with Microwave Heating on Self-Healing Performance of Asphalt Mixture

As an innovative maintenance technology of asphalt pavement,encapsulated rejuvenator used to improve its self-healing performance has been widely investigated by researchers in recent years.In this work,the selfhealing properties of asphalt mixture with and without encapsulations were comparatively studied considering these parameters:Healing time,healing cycles and microwave heating.Three-point bending strength recovery test and fatigue loading cycles recovery test were conducted for two kinds of encapsulations containing the healing agents present inside the asphalt mixture,namely compartmented Ca-alginate/SiO_(2) fiber and compartmented Ca-alginate/graphene oxide fiber.The results showed that the optimum healing time was three days.After the 30 s of microwave heating,the recovery of fatigue loading cycles of asphalt mixture with compartmented Ca-alginate/graphene oxide fiber was four times larger than that of control asphalt mixture.Compared with the single effect related to the encapsulated healing agent or temperature,the synergistic effect of temperature and encapsulation could further significantly improve the self-healing properties of asphalt mixture.The compartmented Ca-alginate/graphene oxide fiber not only could soften asphalt through the encapsulated healing agent to improve self-healing properties of asphalt,but also could repeatedly and quickly heal cracks thanks to microwave action.The synthesis of the fiber breaks the current boundary between the two technologies(capsules healing method and induction healing method)and opens up a new horizon for the asphalt self-healing technology.

Two methodological approaches to assess the seismic vulnerability of masonry bridges

This work describes the seismic vulnerability assessment of a railway masonry arch bridge.Its conservation state is initially investigated by means of a thorough field and laboratory test campaign, comprising destructive and non-destructive tests. Two different methods are used to evaluate the bridge seismic vulnerability. The first method adopts a deterministic approach and corresponds to a single non-linear static analysis, performed as described in the Eurocodes. The second method employs a probabilistic approach and considers the variability of the involved mechanical parameters(structure geometry and properties of the building materials) and seismic parameters(intensity of the action and site conditions). This method associates the probabilistic values of ground acceleration exceedance to the estimated seismic vulnerability. This is shown by means of fragility curves, which allow to take into consideration the uncertainty of the various components involved in the definition of the seismic vulnerability and display the seismic damage scenarios. Currently no code requires to perform this calculation procedure. In addition,this work compares the values of masonry mechanical properties specified in the Eurocodes with those obtained in an extensive investigation campaign involving more than one hundred masonry bridges. Compressive strength and longitudinal elasticity modulus are the relevant mechanical parameters investigated. The outcomes of this research can contribute to the development of a more efficient maintenance system of the masonry bridges belonging to the railway network. This has an important role when it comes to establishing the priority order of assets intervention.

Crushed rocks stabilized with organosilane and lignosulfonate in pavement unbound layers:Repeated load triaxial tests

The creation of the new“Ferry-Free Coastal Highway Route E39”in southwest Norway entails the production of a remarkable quantity of crushed rocks.These resources could be beneficially employed as aggregates in the unbound courses of the highway itself or other road pavements present nearby.Two innovative stabilizing agents,organosilane and lignosulfonate,can significantly enhance the key properties,namely,resilient modulus and resistance against permanent deformation,of the aggregates that are excessively weak in their natural state.The beneficial effect offered by the additives was thoroughly evaluated by performing repeated load triaxial tests.The study adopted the most common numerical models to describe these two key mechanical properties.The increase in the resilient modulus and reduction in the accumulated vertical permanent deformation show the beneficial impact of the additives.Furthermore,a finite element model was created to simulate the repeated load triaxial test by implementing nonlinear elastic and plastic constitutive relationships.