Principal Investigator: Stefan Bossman
About this Project
Brief Project Description & Background
Asphaltic binders that are used for asphalt pavements are obtained mainly from fossil fuels and to a small extent from natural sources. Asphaltic binders are mostly asphalt cements that are dark brown to black in color and are mostly produced by distillation of petroleum crude oils (Brown et al. 2009). Many refineries in the United States are located near water supplied transport or get crude via pipelines from marine terminals. Thus crude oil supply and price in the world market dictate the availability and price of petroleum-based asphalt cement. Most heavy asphalt containing crude oils is imported from Mexico, Venezuela, Canada, and the Middle East. However, in the US Midwest, most asphalt binders used are produced from crudes originating in west Texas and Montana (Canadian). The recent spike in asphalt binder prices has forced rethinking of asphalt paving and enhanced the search for an alternative to petroleum-based asphalt. The price increase of petroleum-based asphalt has made competition from Portland cement concrete more intense. Again due to growing interest in sustainability, a search has been initiated for a non-petroleum binder that could be used for asphalt pavements. The efforts by Colas, S.A. in France and Iowa State University (ISU) in the United States in this respect are notable (Colas 2012; Williams 2012). In 2004, Colas patented a vegetable-based asphalt binder. In October of 2010, a bicycle path in Des Moines, Iowa was paved with asphalt containing 3% bio-oils through a partnership between ISU, the City of Des Moines, and Avello Bioenergy Inc. ISU research efforts to develop bio-binders have used bio-renewable sources, such as triglyceride oils, proteins, starch, and other carbohydrates from different organic sources. A range of different vegetable oils have been investigated by ISU to determine their physical and chemical properties to study their applicability as bio-binders (Raouf and Williams 2010). It is to be noted that if the binder is developed from virgin raw materials, it will be expensive and may compete against the food or edible oil sector. Thus, an alternative approach is needed to develop such bio-binders. Bio-binders can be used in three different ways to decrease the demand for fossil fuel-based bituminous binders: an alternative binder (100% replacement), a bitumen extender (25% to 75% bitumen replacement), or a bitumen modifier (<10% bitumen replacement). Irrespective of the approach taken, the resulting binder rheological properties should have relationships with the following asphalt pavement performance (Brown et al. 2009): (a) Raveling: Raveling can be caused by (i) excessively aged or brittle or the wrong grade of asphalt cement binder and (ii) lack of adhesion of the binder to aggregates; (b) Load-associated cracking: Asphalt cement (AC) consistency influences the development of fatigue cracks. Binders containing polymeric modifiers show some benefits in mitigating fatigue cracks. On the other hand, aged binders demonstrate poor fatigue life in thin AC overlays; (c) Low-temperature cracking: High asphalt cement stiffness at low temperatures is the predominant cause of this type of cracking; (d) Rutting: The high temperature stiffness of the asphalt cement is very important to minimize rutting; and (e) Stripping or Moisture-induced damage: Binders with high viscosity are usually more resistant to moisture damage. However, care must be taken so that low-temperature cracking and reduced fatigue life of asphalt pavements may not happen due to the use of high-viscosity binder.
The primary objective of this study is to develop a modified asphalt binder from bio-refinery by-products and wastes that can be used as a replacement of the bituminous adhesives/binders derived from fossil fuels for asphalt pavements. The secondary objective is to develop a better binder that will have enhanced wettability and coating (adhesion) and resistance to aging (loss of volatiles) properties. The study will consist of five parts: (1) Identification of potential bio-fuel wastes; (2) Binder testing in the laboratory; (3) Devising a simple, heat-mediated approach to change the chemical and physical properties of bio-derived binders and make them similar to petroleum-derived asphalt binders; (4) Binder and mixture testing in the laboratory to find compatibility with the paving asphalt and subsequent mixture performance; (5) Accelerated Pavement Testing of pavements using potential bio-asphalts. Parts (1), (2), and (4) will be addressed in this study. Parts (4) and (5) will be conducted in a project that will be submitted to the Kansas Bio-Science Authority for funding.
The study would result in a bio-binder based substitute for the paving industry. The research has the potential to develop a bio-based asphalt binder industry in Kansas. Since the binder will be from the bio-materials using only heat and air as reagents, these would qualify as “green” materials. Also, the project will offer a solution or use for the wastes from the bio-fuel industry in Kansas.
Due to growing interest in sustainability, Kansas State University has initiated the search for a non-petroleum binder that could be used for asphalt mixtures. The objective of this study is to develop a modified asphalt binder from bio-fuel by-products and wastes that can be used as a replacement of bituminous binders derived from the fossil fuel crude. Initial investigations of the structure and physical properties of bio-fuel-derived heavy oils revealed unexpected chemical differences to petroleum-derived asphalt binders. A simple process for removing the unwanted polar groups from bio-fuel based oils by applying heat will be studied and optimized. Subsequent crosslinking of the bio-based asphalt materials will result in better binder properties, such as enhanced wettability, coating (adhesion) and resistance to aging (loss of volatiles).