Date of Award
Master of Science
Civil, Construction, and Environmental Engineering
R. Christopher Williams
The high amount of scrap tires that are generated annually in the United States are stored in stockpiles, landfills and dumps all over the United States. Tires are mostly composed of rubber; and they can be recycled to obtain two types of ground tire rubber (GTR), ambient and cryogenic. Tire recycling can help reduce the accumulations of scrap tires, while the GTR can be used in many applications in different industries.
The asphalt industry has used GTR in highway pavement construction since the 1960's. GTR can be blended with any conventional asphalt binder to produce asphalt rubber binders, that due to the elastomeric properties of the GTR, will have better performance at high and intermediate temperatures than conventional binders. However, one of the challenges of asphalt rubber technology is its high viscosity, which increases its mixing and compaction temperatures when compared to conventional asphalts.
The objective of this research is to characterize the effects of the binder additive polyoctenamer (PO) on the rheological properties of laboratory-produced asphalt rubber binders with a base asphalt of PG46-34 and two different types of ground tire rubber (ambient and cryogenic); also, to see the effects of PO in the characterization of the performance of asphalt rubber mixtures.
The laboratory-produced binders were evaluated following the Superpave binder specification and testing procedures. Densities, viscosities, complex modulus (G*), mass losses, creep stiffness were obtained from the binders. The statistical analysis performed on the binders demonstrated that the addition of PO improves the viscosities of asphalt rubber thereby obtaining a reduction in the estimated mixing and compaction temperatures. The binder grading demonstrates that PO does not affect negatively the final performance grading for high, intermediate and low temperature. Further, the construction of the master curves showed that asphalt rubber binders with and without PO have similar stiffness performance.
The performances for the dynamic modulus, flow number and indirect tensile strength ratio test of the laboratory-produced mixtures with and without PO were not statistically different. Accordingly, the mixes' master curves showed no difference. Overall, the addition of PO does not negatively affect the performance of asphalt rubber mixes.
Ka Lai Nieve Ng Puga
Ng Puga, Ka Lai Nieve, "Rheology and performance evaluation of Polyoctenamer as Asphalt Rubber modifier in Hot Mix Asphalt" (2013). Graduate Theses and Dissertations. 13279.