A Louisiana State University (LSU) team’s work with a shape memory polymer could potentially not only save the state’s roads but also money and time, according to a post from the school's College of Engineering.
In 2009, LSU Mechanical Engineering Professor Guoqiang Li received a grant from the Transportation Research Board for a project titled, “A Shape Memory Polymer-Based Self-Healing Sealant for Expansion Joint.” The project used a one-way shape memory polymer slab as sealant, which was compressed in a horizontal direction and stretched in a vertical direction before installation. This catered to the seasonal widening and narrowing of expansion joints in concrete pavement. Guoqiang’s team installed the sealant in two joints along CEBA Lane on LSU’s campus in 2011.
In 2012, Guoqiang further improved the idea by developing asphalt-based liquid sealant. He proposed incorporating one-way shape memory polymers with various pre-deformations, or simply by involving a two-way shape memory polymer, which expands upon cooling and contracts upon heating, in an asphalt matrix. A provisional patent was filed in 2013, and a non-provisional patent was filed in 2014 titled, “Liquid Sealant with Thermally Adaptive Properties.” Based on this invention, as concrete freezes and shrinks, the sealant expands to fill the cracks. When the concrete heats up and expands, the sealant shrinks to prevent it from crushing and squeezing out of the channel. According to Guoqiang, the sealants currently used by public workers are made primarily of asphalt, rubber or rubber-modified asphalt.
Lab-scale testing for Phase One of the project has been completed. Phase Two involves working with transportation departments in Louisiana, Texas and Minnesota. In the future, Guoqiang would like to see the shape memory polymer used in concrete design.
Source: LSU College of Engineering