A Study of the Potential Use of Asphalt Containing Synthetic Polymers for Asphalt Paving Mixes.
Date of Award
Doctor of Philosophy (PhD)
William H. Daly
Chemically modified polymer derivatives of potentially useful polymer modifiers from solid wastes, i.e. polyolefins or EPDM, were prepared by chlorination or maleation to improve asphalt blend compatibility. Chlorination of polyethylene can be controlled to convert crystalline HDPE into semicrystalline polymeric additives. Environmental scanning electron microscopy shows that dispersed CPE rich phase was larger than the HDPE rich phase in asphalt blends. Introducing chlorine atoms on polyethylene chains can improve compatibility of the asphalt-polymer blends through adjusting interaction between the components of asphalt and polymer. The grafting of maleic anhydride to polyolefins or EPDM was carried out either in solution or in a melt process in the presence of free radicals. The extent of maleation (1∼2.5%) achieved in either polyolefins or EPDM was determined by FTIR. DSC analysis revealed that all of the maleated polypropylene derivates were at least 45% amorphous. Most of maleated polymer/asphalt blends exhibited lower activation energies of flow and improved rhelogical properties relative to those of the pure asphalt matrix. Standard procedures for studying the physical and engineering properties of asphalt binders have been used to specify the PG grading of the blends according to Superpave protocols. The polymer/asphalt blends have significantly better properties than those of tank asphalts. The blends exhibit higher viscosity at high temperature, higher rutting resistance, reducing age hardening for longterm temperature cracking, and lower creep stiffness at low-temperature cracking response than tank asphalts. A laboratory study was conducted to examine the feasibility of using CPE as modifier to paving grade asphalt. Both a binder rheology study and a mixture characterization were conducted to compare the performance of conventional dense graded mix containing ACL-2 and CPE modified ACL-2. In general, the addition of CPE has improved the mix properties as measured from the indirect tensile strength tests, indirect resilient modulus test, indirect creep test, and fatigue test. The binder rheology correlated well with mix properties. The CPE-modified HMAC mix did show improved fundamental engineering properties relative to tank asphalt at all tested temperatures.
Yeh, Pei-hung, "A Study of the Potential Use of Asphalt Containing Synthetic Polymers for Asphalt Paving Mixes." (2000). LSU Historical Dissertations and Theses. 7402.