Extreme climates pose tough duty cycles and challenges for testing procedures

This month we look at how pavement testing technology is responding to extremes of temperature, showcase concrete testing in Doha and look at how water drops could help identify delaminated bridge decks - Kristina Smith reports One of the biggest challenges that pavement engineers face is how to design for extremes of temperature. Designing for cold weather can result in problems at higher temperatures – and vice versa. In Scandinavia, generally a cold climate, they are facing this problem. In the summer,
April 5, 2013 Read time: 3 mins
In desert conditions daytime ambient temperatures can easily reach 50°C while conditions are much colder at night, providing tough duty cycles for asphalt surfaces

This month we look at how pavement testing technology is responding to extremes of temperature, showcase concrete testing in Doha and look at how water drops could help identify delaminated bridge decks - Kristina Smith reports

One of the biggest challenges that pavement engineers face is how to design for extremes of temperature. Designing for cold weather can result in problems at higher temperatures – and vice versa.

In Scandinavia, generally a cold climate, they are facing this problem. In the summer, temperatures in the pavement can reach 50°C when the sun shines for more than 20 hours. This means that rutting is one of the most frequent problems on roads carrying heavy traffic.

Researchers at the Swedish Road and Transport Research Institute, 7264 VTI, have developed a new shear box test which can evaluate the shearing and viscosity properties of bituminous materials at different temperatures and different traffic speeds. These properties are good indicators of an asphalt mixture’s resistance to deformation under moving loads.

“This method will help us get the optimum solution for a pavement design,” said Hassan Hakim, who with CTI colleague Safwat Said has carried out the research. “We can use a modified bitumen and understand how the asphalt changes due to the temperature. That way we can find something that is more resistant in the hot weather but still soft in the cold weather.”

The shear test involved gluing a cylindrical specimen to two plates. One plate exerts a sinusoidal force, mimicking acceleration or braking force while the other applies a constant compressive force equivalent to the weight of the vehicle. The frequency of the sinusoidal load and the temperatures are varied.

VTI has also gone on to create a model which can estimate the rutting development in the pavement. Hakim said that VTI has compared the model’s predictions against the actual rutting on a road which has been in use for 10 years with “good results.”

VTI also offers a Prall tester, which was launched in early 2012, required for climates such as Scandinavia where studded tyres are used in winter weather.  The VTI Prall is designed to meet the requirements for method A in the European standard EN 12697-16:2004 “Bituminous mixtures- Test methods for hot mix asphalt- Part 16: Abrasion by studded tyres.”

VTI would like to make it clear that it was not involved with the development of  the Cooper Prall tester, as stated in the May 2012 issue of World Highways and that its Prall tester is commercially available.

Water droplets could help detect bridge damage

Researchers at Brigham Young University in the US have discovered a potential new means of testing the integrity of bridges: dropping water onto the deck and recording the sound.

Brian Mazzeo and W Spencer Guthrie reported the results of their study ‘Acoustic impact-echo investigation of concrete delaminations using liquid droplet excitation’ in the journal Non-Destructive Testing and Evaluation International.

Impact-echo testing is often used on bridges and other structures. Engineers drag heavy chains over the bridge deck and listen to the sound it makes. Where a concrete structure has delaminated, often due to rusting reinforcement, a different sound is heard.

This method can be costly and disruptive, however, as it often requires lane closures. If the sound of water droplets, sprayed over the deck from a moving vehicle could be used, it would vastly speed up the process.

It is early days for this new method of testing. More research will be required before these findings can be developed into a useable solution.

Asphalt milling, paving & compaction

For more information on companies in this article

VTI

Related Content

  • CET opens new laboratory to service UK’s infrastructure projects
    October 23, 2017
    With over £300 billion of investment in infrastructure planned over the next four years in the UK, materials testing firm CET is gearing up to service a lot more projects – Kristina Smith visited the newest laboratory near Heathrow to find out more. The CET Group has ambitious plans. Over the next four years it wants to double the size of its business, which in the last year turned over £27 million. “There’s a lot of positivity out there,” said Gary Corrigan, managing director of the group’s infrastructu
    Read More
  • Stiffer roads, less fuel?
    October 19, 2020
    Researchers at the Massachusetts Institute of Technology looked at how much fuel – and, hence carbon – could be saved by making roads in the US stiffer. They concluded that by resurfacing 10% of roads every year for the next 50 years, 0.5% of total transport emissions, or 440 megatons, would be saved over that period.
    Read More
  • Turkmenistan’s new bridge features novel waterproofing
    November 8, 2017
    Turkmenistan’s new bridge is benefiting from a novel sealing system that will optimise working life as well as maximising safety. A novel waterproofing solution is being utilised for the Turkmenabat - Farap Bridge in Turkmenistan. The project is of note as the structure is the longest metal span bridge in Central Asia. The client for the project is the state-owned firm Turkmenavtohowayollary, while the general contractor is Altcom Road Construction and the consultant engineer is Soyuztransproekt. Stirling
    Read More
  • Review of the research activities on the behaviour of Iterlene
    November 2, 2012
    The use of reclaimed asphalt pavement (RAP) is common practice in many countries. The aged bitumen from RAP has a lower penetration and is more viscous than it was when first mixed. The reclaimed bitumen is generally balanced by the addition of fresh binder softer than the traditional one used to produce hot mixes. However, balancing penetration and softening point or viscosity does not produce an identical bitumen to the original one. One fundamental option is the regeneration of the aged binder in order t
    Read More

Highlighted Content