- Louisiana State University mechanical engineering professor Guoqiang Li has invented a new type of sealant that could help put an end to the pavement cracks that plague America's roads and highways, according to the LSU College of Engineering.
- Guoqiang first developed his shape memory polymer-based sealant using a 2009 Highway IDEA award from the National Cooperative Highway Research Program and additional funds from the Louisiana Research Transportation Center. He first used a one-way memory shape polymer — compressed horizontally and then stretched vertically — to produce a sealant that could mitigate the effects of the seasonal expansion and contraction of concrete pavement. Then, in 2012, Guoqiang began using a two-way shape memory polymer combined with asphalt to create a better bond with the concrete. The resulting product expands to fill cracks as concrete freezes and contracts when heat forces the concrete to expand so that the sealant doesn't squeeze out of the cracks. The addition of asphalt also reduces the cost of the sealant and can slow down the deterioration of the sealant from environmental factors like ultraviolet radiation.
- Phase one lab testing is complete, and the next phase will see transportation departments in Louisiana, Texas and Minnesota test the sealant. Texas officials will certify the material while Louisiana and Minnesota will conduct traffic wear and tear and freezing-temperature tests, respectively, with the process expected to wrap up in 2019. Guoqiang said this shape memory polymer could also one day be incorporated into a concrete design, possibly assisting post-disaster recovery efforts by contracting into its original shape when heated.
Minneapolis officials have to contend with the damage that freeze-thaw cycles can do its roads — including potholes and cracked expansion joints — and one of the latest approaches it has used to try to extend the life of its pavement is a program of concrete pavement preservation (CPP).
The Concrete Street Rehabilitation Program uses various CPP techniques, including slab stabilization and crack resealing, on large areas of damaged concrete that are otherwise sound and can still perform well through its useful life. The city expects the program, which will see the preservation of up to four miles of residential roads a year, to save money in the long run by helping it to avoid having to make more substantial, expensive repairs.
When concrete is beyond preventive maintenance, however, sometimes pavement must be replaced, and there are inroads being made in this area as well. In Louisiana, state transportation officials recently replaced an Interstate 20 entrance ramp near Greenwood with a $2.8 million precast concrete pavement panel system. The state is testing out the durability of the panels, but costs are likely too high for it to be rolled out for major projects even if the material proves to be stronger than traditional highway construction methods.