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What Makes A Better Highway?

Published: September 15, 2014

Shadi Saadeh recently returned to campus after a sabbatical spent thinking about what makes a better highway.

The member of the Civil Engineering and Construction Engineering Management Department since 2007 is an expert on highways and the materials that compose them. He spent his recent sabbatical putting together an article on discrete element modeling and how to predict materials response which will help Southern California highways better resist burning heat and crushing loads for the Journal of the Transportation Research Board.

Saadeh’s sabbatical research concluded that the discrete modeling system is a valid way to simulate the response of a freeway’s asphalt concrete material.

“This modeling system is useful for any city, county or state that wants to pave a road,” he explained. “Any of these would like to know how long the road will last and what kind of stresses it will encounter. The article presents a quality control test for Hot Mix Asphalt. The discrete element modeling is used to simulate the test.”

Saadeh believes the rivers of asphalt that crisscross the state do so in a flood of materials that have come a long way since all roads led to Rome.

“Those materials have changed a lot in 2,000 years,” he said. Asphalt mixtures can be as simple as mixing binder with aggregates but, today, something new has been added. “It is now possible to add recyclable materials such as rubber to pavement,” he explained. “There are many ways to recycle the tens of millions of tires sold every year. One way to do that is to put the tires back into the road which is quite different from what they did in Rome.”

More changes are due, including additives that help tomorrow’s pavements better resist the heat.

“What we want to do is to develop new tests to better understand tomorrow’s pavements,” he said. “For instance, additives are used now to produce warm mix asphalt at lower temperatures compared to the conventional hot mix asphalt.”

Saadeh’s research is as timely as this morning’s commute. “We, as a nation, must pay attention to our infrastructure,” he said. “The American Society of Civil Engineers has graded America’s infrastructure with a ‘D’ and we must allocate a bigger portion of our budgets to change that.”

State universities have a role to play. “A life cycle cost analysis can estimate how long pavement will last,” he said. “I work with faculty members at Chico State and Cal Poly San Luis Obispo to help Caltrans at every level to test new technologies for pavement. Sometimes we offer training. This is what state universities have to offer.”

Saadeh’s research not only strengthens roads but acts as a teaching tool. “I discuss my research with my undergraduates and graduates all the time,” he recalled. “When the California Asphalt Pavement Association hosts conferences, I attend along with students from undergraduate and graduate classes as we did this April in Ontario.”

His hot mix course is unique in the CSU. “This is the only campus that I know of among the many that ring CSULB such as CSU Northridge, UCLA and Caltech which offers a faculty member whose expertise is hot mix asphalt,” he said. “This is the only campus among all of them that offers such a course. This gives our students an experience that can lead to such achievements as the presentation by one of my graduate students before the Association of Asphalt Pavement Technologists.”

One of the advantages to Saadeh’s research is performing it in Long Beach. “From here, we can reach every kind of weather pavement can face,” he said. “If you want to test materials meant for pavement in hot weather, you test in Mexicali. If you want to test materials meant for pavement in cold, you try Big Bear. Geographical location plays an important role in this research.”

Saadeh’s expertise affects his worldview. “I want to make pavement stronger and longer-lasting. No one would expect a 20-year-old car to perform like new. Why should we expect 20-year-old pavement to be any different? We have to pay more political attention to our roads,” he said.

Saadeh worked for the Texas Transportation Institute and the Louisiana Transportation Research Center before joining CSULB in 2007. He received his Bachelor of Science degree in civil engineering from the University of Jordan in 1997, his Master of Science degree in civil engineering from Washington State University in 2002 and his doctorate in civil engineering from Texas A&M University in 2005.

Saadeh plans to continue his highway research. “I’m working with a colleague in chemical engineering to determine the value of adding titanium dioxide to pavements to help them react better to pollutants coming from vehicles,” he said. “How can we streamline that and how we make tomorrow’s roads while contributing to a clean environment?”