Hashim R. Rizvi

Mechanistic Characteristics of Asphalt Binder and Asphalt Matrix Modified with Nano-Fibers

The Hot Mix Asphalt (HMA) mainly consists of air voids, coarse aggregate and asphalt matrix (AM), which includes asphalt cement (AC) and fine aggregates. The coarse aggregate is stiffer than the AM and is elastic in nature, whereas, the AM makes the HMA a visco-elastic material. The AM is considerably weaker than the coarse aggregate and highly susceptible to damage due to external loads and environment. This study focuses on the preparation and mechanistic characterization of AC and AM mixtures modified with Carbon Nano-fibers (CNF). The AM mixtures were made using lime-stone aggregates and three AC types, neat, processed and CNF-modified. The AC was modified with varying percentage of CNF by weight of AC. To achieve the highest degree of CNF dispersion in AC, two different dispersion techniques were utilized. First, the CNF were sonicated for a specified time to initially disperse them into a solvent. Then the mixture was mixed with AC using a mechanical mixer at medium to high temperature. The dynamic shear rheometer was utilized to determine complex shear modulus (G*) and creep compliance (J[t]) of AC and AM mixtures for a range of temperatures and loading frequencies. The G*-master curve and J[t] analysis revealed that the AC modified with CNF significantly improves the visco-elastic response of the AC and AM. It is recommended to expand the research to different types of aggregate, aggregate gradation, and types of asphalt in order to identify key parameters that can facilitate the understanding of improvements in HMA performance using nano-fibers.

Bone Glue Modified Asphalt: A Step towards Energy Conservation and Environment Friendly Modified Asphalts

Asphalt has been modified for the past several decades using various additives, including synthetic polymers. Polymer modification improves structural and engineering characteristics of the binder, which is a result of improvement in rheological characteristics of binder as well as its adhesion capability with the aggregate. Such enhancement inevitably enhances the performance characteristics of hot mix asphalts (HMA) such as fatigue life, resistance to rutting, and thermal cracking. Even though polymer-modified HMA is popular in North America and European countries, its use is still limited in developing countries of Southeast Asia due to high costs associated with its manufacturing, processing, and energy consumption. In this study, a new kind of asphalt modifier derived from animal wastes, such as bones, hides, and flesh commonly known as Bone Glue, is studied. This biomaterial which is a by-product of food and cattle industries is cheap, conveniently available, and produced locally in developing countries. The results of the research study showed that the bone glue can easily be mixed with asphalt without significantly altering the asphalt binders viscosity and mixing and compaction temperatures of HMA. Additionally, improvements in complex shear modulus for a range of temperatures were also determined and it was found that complex shear modulus was improved by bone glue modification.

Development and Evaluation of Functional Open Graded Friction Courses (FOGFC) Mixtures for In Situ Highway Runoff Treatment

The use of Open Graded Friction Course (OGFC) pavements as road surfacing materials has grown considerably over the past decades. Acknowledged benefits include reduced splash and spray, better visibility, better traction, and less noise. Moreover, the installation of OGFC shows noticeable improvements of runoff water quality, which might be due to the retention of pollutants by internal pores. However, the traditional OGFC has little or no effects on the dissolved constituents, such as dissolved organic matter, dissolved copper and zinc in the stormwater. This study was conducted to correct this problem by adding additives into the OGFC mixtures to produce Functional OGFC (FOGFC), which has adsorption functions for dissolved constituents, such as organic matters and dissolved heavy metals commonly found in highway stormwater runoffs. The characteristics and environmental applications of this novel FOGFC were evaluated. Results indicated that FOGFC not only preserves OGFC’s advantages in the removal of particulate pollutants, but also significantly extends its ability to remove non-particulates or dissolved pollutants, thus eliminating the needs of external treatment facilities to a certain extent.

Highway Runoff In Situ Treatment: Copper and Zinc Removal through MOGFC

AbstractThe primary objective of this study is to develop and evaluate multifunctional open-graded friction course (MOGFC) for use as an in situ treatment technique to remove Cu and Zn from highway runoff. First, the conventional porous pavement, open-graded friction course (OGFC), was prepared with varying air voids. Five different types of adsorbents were selected based on cost, applicability, and availability. Second, MOGFC was prepared by adding different adsorbents into the void of OGFC. A series of laboratory tests were conducted to evaluate the adsorption capacity of the adsorbents and metal removal efficiency of MOGFC. The tests included air void content, permeability, moisture susceptibility of OGFC and MOGFC, batch adsorption study of adsorbents, and metal removal by MOGFC. Results showed that three adsorbents have moderate to high adsorption capacity for copper (Cu) and zinc (Zn) removal from its aqueous solution. With these adsorbents, MOGFC could also considerably reduce metal concentration f...