Since climate is changing at a sudden rate, lately there has been a widespread discussion going on about the ways how to stop catastrophes that may result from this. In the last decade there has been a bewildering increase in average temperature values and rise in sea levels, which impact pavement materials. This means that they have a negative effect on transport networks. Researchers have shown a rising focus on this topic. Civil engineers are involved in planning, construction and maintenance of roads, and their main responsibility is to design practical measures of pavement materials to manage the impacts of climate change. To best manage this issue are required a wide range of skills from sketching to paving. This paper will present the consequences of weather patterns on transportation infrastructure.
Swaps in the statistical distribution of atmospheric conditions patterns that persist for an extended period of time are known as climate changes. As one of the most significant obstacles the world faces nowadays, climate change is expected to trigger harmful domino effects in current urban infrastructure systems as a consequence of an increase in the immensity and frequency (rate of occurrence) of hazardous weather events. The first step in decreasing hazards to infrastructure systems is the recognition of infrastructure interconnections and climate effects. Globally, more than $2.5 trillion a year is spent on infrastructure (AidData, 2017). This investment is immense, permanent and irreparable with a long duration that has slight alternative utilization. It is normally planned to endure decades, over which time predicted changes in the climate will make alterations to infrastructure functioning.
The past decade has seen rapid weather changes and recently, researchers have shown an increased interest in the way it affects infrastructure. Since we travel almost every day and drive on different pavements it is becoming extremely difficult to ignore climate changes, and the impact that they have in road infrastructure. This paper seeks to intensify understanding of these hazards caused by climate changes and try to give solutions for pavement structures that will maximize performance and minimize risks. It will investigate the current state of road infrastructure and present the impact that climate change has on it.
Background: Climate Risk Assessment
It is a fact that climate change is having a rapidly increasing effect in every aspect. Among them we can mention: sea level rise from 0.09 to 0.88m; reduction in rainfalls in some place and considerable increases in others; increase in evaporation; range expansion of cyclonic events etc. (IPCC AR5, 2014). It is a major threat to road infrastructure, since it directly impacts annual rainfall with extreme events that will cause floods, moisture, wet and dry cycles etc. The question that arises is how these actually impact roads and transportation, and what can we do, if possible, to reduce these hazards?
Road Infrastructure Planning and Management
The road pavement is a structure which consists of assorted layers of materials that act together to supply the actual surface on which vehicles travel. Generally they are composed of solid, liquid, and gaseous phases. The solid phase is thicker and made of cement and concrete, which are the most durable materials and resistant to extreme weather events (Boikovaa, Solovyova, Solovyova, 2017). The upper layers comprise bitumen. Bituminous pavements are typically designed for a 20-year lifespan and concrete ones for 40 years. Pavement materials that are used in construction must meet these seven basic requirements:
- Volume stability
- Wear resistance
- Impermeability (Lay, 1990)
When developing a new road proposal some objectives and consequences must be taken into account. The prior planning and analyses will ensure that any constructed scheme will return net benefits to the community. Roads provide a necessary facility to humans in their lives. In 2015, 1.282 billion vehicles were in operation worldwide (Statista, 2015). More than $2.5 trillion is spent on infrastructure per year. As a result, the price of maintenance for roads is the largest outlay for governments. Such budgets may cover forward periods of up to ten years and must therefore be based on best estimates of future conditions. They require consideration of planning, control and forecasting of events, especially climate changes.
Effects on Road Materials
Road pavements are planned for different climates, from dry deserts to the alpine ones. Even though the changes in climate are likely to be restrained and manageable, increases in temperature will affect bitumen and asphalt. Bitumen is temperature sensible, so resurfacing will be needed more often, because of rapid oxidation (Fazaeli, 2012). In the design of thick asphalt, especially in highways, the weighted mean annual pavement temperature (WMAPT) is taken in consideration. It is expected that climate change will affect WMAPT, which will result in thicker asphalt to accommodate the lowering of its stiffness (Halle, 2012). Also if heavy vehicles exert great forces on these roads, then a more expensive bitume will be utilized to cover pavement surfaces.
The lowest layer of pavements is made up of granular materials, which show an unsatisfactory performance under water effects. If there will be frequent rainfalls and dry cycles due to climate change, then the water levels in coastal areas will rise. This means that the sea level will rise too (Žiliǌtơ, 2016). Because of this, the use of more stabilized materials to lift pavements is necessary, but these materials cost more and it is likely to be impossible to use them since the majority of roads are already constructed and located.
Another material that is used in road construction is saline water because of drought, and in this way salt is gathered in pavement materials during compaction of granular basecourses. Pavements consist of a spray seal layer which is found between bitume and concrete. The use of saline water will inhibit spray seals attaching to the underlying layers. When the temperatures increase, the presence of salt will worsen the shrink/swell behaviour, which causes more edge cracking of sealed surfaces. Due to this, more maintenance activities are needed.