Date of Award

May 2023

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Engineering

First Advisor

Konstantin Sobolev

Committee Members

Habib Tabatabai, Emil Bautista, Michael Nosonovsky, Xiao Qin

Abstract

In order to establish a cost-effective and enduring road infrastructure, it is imperative to employ inventive methodologies that prioritize environmental sustainability. The current climate necessitates the development of a sustainable, enduring, and effective road infrastructure that requires minimal maintenance, however, achieving this goal is an effortful undertaking, and necessitates urgent and groundbreaking technological advancements. The use of fillers (aggregates with a diameter smaller than 75 µm) in asphalt mix design is a common practice in the pavement industry. They can occupy up to 12% by weight in asphalt mixes. The inclusion of fillers in asphalt mix, even in limited concentrations, has a significant impact on the properties of the mix. Limited studies have been conducted on using Portland Cement (PC) as a filler in asphalt pavement. Portland cement has the potential to improve the rheological, mechanical and durability properties of asphalt concrete. The incorporation of polymers in asphalt has been found to enhance its performance by increasing resistance to cracking, rutting, fatigue damage, and temperature susceptibility. Polymer-modified binders have been successfully applied in high-stress areas, such as airports and busy roads. Various types of polymers have been utilized to modify asphalt for improved properties. The use of Hot Mix Asphalt (HMA) in pavements causes environmental harm due to high CO2 emissions and energy consumption. Warm Mix Asphalt (WMA) is gaining popularity because it offers numerous technical, environmental, and economic benefits such as improved workability, reduced emissions and energy consumption, better working conditions, less binder aging, and extended construction time. The objective of the current study is to investigate the effect of PC incorporation, warm-mix addition, and polymer modification on the properties of asphalt materials. The study was divided into two phases: phase one was mastic level, in which the rheological properties of asphalt binders and asphalt mastics (binder + filler) were discussed, while phase 2 was focused on the mechanical response of asphalt concrete (binder +filler + aggregates). In phase 1, first, PC reactive powder and Limestone (LS) as a reference filler were physically, chemically, and morphologically characterized. Thereafter, the filler/ powder was incorporated into HMA and WMA plain and polymer-modified asphalt binders at filler volume concentrations of 0, 10, and 25% as a partial replacement of asphalt binder, using a blade speed mixer. The binders used in this study were PG58-28, polymer modified PG58-28, PG64-10, and polymer modified PG64-10. The first two binders are commonly used in northern states if the U.S., while the second two binders are widely utilized in the U.S. southern states. Totally 40 mastics were made and tested. The high-temperature investigated rheological properties included viscosity, complex modulus (G*), phase angle (δ), rutting resistance (G*/sin(δ)) and multiple stress and creep and recovery. The research results demonstrated that filler/powder incorporation and polymer modification leads to an increase in the viscosity of the mastics, while warm-mix addition reduces the viscosity. Further, it was noted that filler incorporation and polymer-modification improved the complex modulus and rutting resistance of the mastics. While phase angle remained unaffected from filler incorporation, warm-and mix addition, polymer modification resulted in a reduction in the phase angle, making the mastics have a more elastic response With regards to multiple stress and creep and recovery test results, it was observed that filler incorporation and polymer modification resulted in an enhancement in J value and recovery percentage of the mastics. Moreover, the mastics containing PC reactive powder and based on PG64-10 and polymer-modified PG64-10 asphalt binders outperformed the mastics containing LS filler at different filler volume concentrations and different temperatures. The intermediate rheological performance of the mastics was evaluated by performing a fatigue test. The research results demonstrated that warm-mix additives, due to the softening effect improved the fatigue response of the mastics. Further, PC-based mastics had a better fatigue performance in most of the cases, when compared with LS-based mastics. Low-temperature performance of the mastics was assessed by conducting Bending Beam Rheometer (BBR) and Dynamic Mechanical Analysis (DMA) tests. It was noted that filler incorporation led to more brittle behavior of the mastics, polymer modification led to a relatively similar rheological response, while warm-mix additives reduced the stiffness of the investigated mastics at low temperatures. In phase 2 of the study, eight (8) WMA mixtures based on PG58-28, polymer-modified PG58-28, and polymer-modified PG64-10, and with filler volume concentrations of 0 and 40%were made and tested. The evaluated parameters included constructability, moisture susceptibility, and fatigue resistance. In terms of constructability, PG58-28 and polymer-modified PG58-28 mixtures containing PC reactive powder needed less compaction effort to reach desired density. Moreover, such mixtures showed higher strengths under indirect tensile test and had a similar or better resistance against moisture damage. The reported results from the fatigue test demonstrated that the mixtures containing PC reactive powder can undergo larger fatigue loads with a lower deformation rate, which helps them to be more durable under traffic loading in the roads. Overall, it can be concluded that the use of PC reactive powder in a hybrid WMA asphalt system can be a sustainable alternative from economic, environmental, and durability points of view.

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