C. J. Glover

Bio: C. J. Glover is an academic researcher from Texas A&M University. The author has contributed to research in topics: Asphaltene & Asphalt. The author has an hindex of 26, co-authored 48 publications receiving 2173 citations. Previous affiliations of C. J. Glover include Rice University & Texas A&M Transportation Institute.

Development of a New Method for Assessing Asphalt Binder Durability with Field Validation

Abstract: This project was a comprehensive study directed at developing an improved method of screening asphalt binders for long-term pavement performance. A new dynamic shear rheometer (DSR) function, G'/(eta'/G'), and a new aging procedure should warn of premature asphalt hardening and resulting fatigue cracking. For unmodified asphalts the new DSR function correlated well with ductility (at 15 deg C, 1 cm/min) below 10 cm. The correlation was originally developed for DSR measurements at 15 deg C and 0.005 rad/s. These conditions were time-temperature superposition shifted to 44.7 deg C and 10 rad/s to produce a method that is easily accessible to standard laboratory rheological equipment and methods. The recommended aging procedure uses the pressure aging vessel (PAV) apparatus but takes advantage of the higher average aging rate when the asphalt is aged in thinner films. This change, combined with somewhat longer aging, results in a more rigorous test of durability than the standard PAV method. At the same time, the resulting rankings of aged materials are more representative of rankings that are obtained from aging at atmospheric air pressure and 60 deg C. For modified asphalts, the results were complex. Generally for a given value of the DSR function, the ductility was better than indicated by the unmodified asphalt DSR-ductility correlation. Larger amounts of modifier produced increasing values of ductility for a given function value. This result was very asphalt dependent, however, so no general correlation could be found. As modified binders oxidize, the asphalt hardens and the improvement to ductility imparted by modifiers decreases. After enough aging, the improvement is gone and modified binders perform no better than their aged unmodified counterpart. A critical issue is whether the life extension produced by modifiers is life-cycle cost effective. Long-Term Pavement Performance (LTPP) and SH 21 binders indicate: sealcoats may provide an opportunity for significant and very cost-effective in-place binder rejuvenation; G'/(eta'/G') is an excellent function for tracking pavement aging; pavements can oxidize rather uniformly with depth; brittle binders can be tolerated in stiff pavements; aggregates appear to have little effect on asphalt oxidation reactions; rolling thin-film oven tests plus PAV aging is not severe aging, in the context of pavement life.

The kinetics of carbonyl formation in asphalt

Abstract: The oxidation of asphalt is a major cause of pavement failure. The low-temperature oxidation kinetics of 14 asphalts are presented. At constant temperature and oxygen pressure, asphalt oxidation occurs in two stages: (1) a relatively rapid-rate period, followed by (2) a long period of constant rate. Activation energies for the constant-rate region vary from 64 to 109 kJ/mol, and reaction orders relative to oxygen pressure vary from 0.25 to 0.61. This variation in activation energy and reaction order leads to skepticism regarding the present practices of evaluating road-condition asphalt-hardening rates at a single elevated temperature and perhaps at an elevated pressure. The asphalts occur in essentially two groups, one at high values of both activation energy and reaction order and the other at low values of each. The data indicate the existence of an isokinetic temperature near 100 C. The degree of oxidation that occurs during the initial rapid-rate region varies inversely with the oxygen reaction order of the constant-rate region.

An Investigation of Asphalt Durability: Relationships Between Ductility and Rheological Properties for Unmodified Asphalts

Abstract: Literature reports indicate that the ductility of binders recovered from asphalt pavements correlate with cracking failure. However, ductility measurement is a time and material consuming process, ...

Oxygen Uptake As Correlated to Carbonyl Growth in Aged Asphalts and Asphalt Corbett Fractions

Abstract: Ten asphalts, including seven Strategic Highway Research Program (SHRP) asphalts and three Texas asphalts, plus naphthene and polar aromatic Corbett fractions for five of the seven SHRP asphalts were aged at laboratory conditions. The oxygen content by direct measurement and the FTIR carbonyl content were obtained for samples which were aged to varying degrees. It was found that, for each material, the oxygen content correlates linearly with the carbonyl content. The correlation is independent of aging temperature and aging pressure over the ranges studied. Furthermore, each material has a unique correlation coefficient, and the correlation slope for a whole asphalt is smaller than those of its fractions, except for asphalt AAM-1. Since the major oxidation products, including ketones, carboxylic acids, and anhydrides, have different oxygen content-carbonyl content ratios, the correlation coefficients provide qualitative information about the distribution of oxidation products. Relations between oxygen, carbonyl, and asphaltene production are deduced from these and earlier results.

The epsilon-(gamma-glutamyl)lysine crosslink and the catalytic role of transglutaminases.

Abstract: Publisher Summary The production of functional protein units in many cases requires the formation of covalent bonds, and prevalent among these are crosslinks within and between molecules that play a major role in maintaining gross forms of structure and limiting degrees of extensibility. This chapter describes the current knowledge of the distribution, formation, and function of the ɛ-(γ-glutamyl)lysine crosslink, and focuses largely on the crosslink known to be or believed to be formed by the catalytic action of transglutaminases. These enzymes catalyze a calcium-dependent acyl-transfer reaction in which the γ-carboxamide groups of peptide-bound glutamine residues are the acyl donors. Participation of ɛ-amino groups of peptide-bound lysine residues as acyl acceptors yields ɛ-(γ-glutamyl)lysine crosslinks. Although, there is a little doubt that the enzymes described in the chapter are capable of catalyzing crosslink formation, individualities of substrate preference notwithstanding, current data do not prove that this is the biological function of each. The chapter is believed to permit critical evaluation of the information available, suggest areas that hold the greatest opportunity for advances, and will, as a consequence, stimulate further investigations of the synthesis, distribution, and function of the ɛ-(γ-glutamyl)lysine crosslink.