Modern crude oil refining and bitumen production technologies are having a global impact on bitumen quality, consistency, and functionality. As a result, the industry is shifting to a new mentality of developing clear, attainable performance criteria to design quality mixes without relying on suppliers to dictate quality.  

Here, we will take a closer look at bitumen quality and the shifts taking place in today’s bitumen marketplace including changes to how bitumen is sourced, procured, and incorporated into balanced mix design to address performance.  

A number of factors affect bitumen quality for paving and roofing applications. Bitumen is no longer locally sourced from a single supplier in most regions. Instead, bitumen is sourced globally from different suppliers with different specifications. It is also not uncommon for suppliers to incorporate modifiers, bio-additives, extenders, and other additives into the bitumen before shipping it out.  

Bitumen has also become less of a necessary byproduct for producers in the wake of coking (or catalytic cracking), block running, synthetic crude use, and shale oil production. The result is that it is no longer abundantly produced or with much attention to quality, leaving the responsibility for performance on those incorporating the material in their projects.  

Variations in bitumen quality are likely the new normal given economic and global drivers. Bitumen is a byproduct of crude oil refining, a process that has evolved greatly in recent decades. The advent of catalytic cracking in the early 2000s enabled refineries to maximize their production of other products, limiting the amount and quality bitumen left over. Demand has driven global sourcing of bitumen, which also results in variable characteristics and quality since different sources can yield different chemistries.  

The refining process has been largely optimized by suppliers to maximize fuel components, and this may limit the amount of bitumen left over. With fewer refineries in operation than just decades ago and the elimination of topping refineries, bitumen production is more limited. The introduction of synthetic crudes and shale oil has also limited bitumen supply.   

These factors have driven industries to obtain bitumen from multiple suppliers across different sources of crude oils. Importantly, different crude oils yield different grades and qualities of bitumen. Blending these different materials results in bitumen with different characteristics. This can result in bitumen with different functional properties that manifest in roadway and roofing applications when incorporated into a mix or product.  

Virgin bitumen is typically sourced globally from a variety of suppliers, largely driven by economics. Since bitumen is no longer a critical byproduct for refineries, producers tend to limit supply and, subsequently, drive up demand and pricing. The market’s response has been to source bitumen from various suppliers to find the best pricing, leading to variable characteristics and quality in the final material delivered to a plant for use.  

Bitumen quality and cost are impacted by the suppliers used for sourcing the material. Historically, plants would procure bitumen on a local or regional basis, often repeatedly from the same supplier. This provided a level of consistency in bitumen quality and expectations. However, with fewer refineries, less bitumen on the market, and a global marketplace driving costs, companies are procuring crude oils and bitumen across suppliers on a worldwide basis. Additionally, Integrated Traders are standing in to set pricing and move bitumen across markets with little interest in consistency of quality. The result is a more variable bitumen product that can have different chemistries and functional characteristics that must be addressed before they are put to use in a viable mix. 

Various crude oil sources can produce bitumen with different qualities and characteristics. Crude oil slates are the blend of crudes used by a refinery to produce various products during the refining. Bitumen is considered a byproduct of this process, a leftover material that, with the onset of catalytic cracking and other refining optimization efforts, has been reduced in importance for refiners. Sourcing from different refineries that use different crude oil slates and varying approaches to refining results in bitumen that will have different quality from supplier to supplier, and delivery to delivery.  

Not all refineries approach fractionation in the same way, using techniques that help them optimize non-bitumen output, which is often more cost advantageous. The resulting bitumen across refineries and crude slates can have different chemistries that produce different functional characteristics when used in mixes for paving and roofing applications.  

With bitumen quality a variable on the global market, contractors and plants are looking to address the variations in product to produce mixes to specification. One approach is to consider mix-targeted specifications rather than relying solely on bitumen parameters. While bitumen quality and chemistries change, mix designers can work to take a substandard bitumen and create a high-performing mix with a focus on functional properties. This can include the use of modifiers and additives that impact functional characteristics without restoring the chemical composition of the bitumen itself. Blending of different bitumens that do not individually meet quality specs, but when blended may meet specs, is also another commonly used technique. 

Bitumen has a unique chemical composition that can vary depending on the crude oil slate it was sourced from, the refining process, and how it has been blended and/or modified by the supplier before it arrives at a plant. Plants can incorporate additives into their mix design to balance out the functional properties of the mix and make up for any inconsistencies or poor performing characteristics of the bitumen. 

Virgin bitumen is often evaluated based on different factors including PG Grading, softening point, penetration point, and viscosity. When incorporated into a balanced mix design, testing includes evaluation on the functional characteristics of an intended mix sample. This can include tests for cracking resistance (Glover-Row Parameter, IDEAL-CT), aging (Delta Tc), rutting (Hamburg Wheel Tracking), stiffness (Resilient Modulus), and mechanical strength (Tensile Strength Retention). Mix designers should establish clear and precise performance specifications that can guide binder, aggregate, and additive selection to produce a viable, high-performing mix. 

Bitumen Quality and Sripath® 

Sripath understands that bitumen quality is more inconsistent than ever before as plants and contractors grapple with stringent performance requirements and globally sourced, variable bitumen for their mixes. Sripath’s diverse product portfolio includes solutions that enhance bitumen performance by adjusting the functional properties of mix. The result can be paving and roofing solutions that exhibit durable performance while adhering to sustainability guidelines. Sripath’s innovative engineered materials include a range of rejuvenators, oils, and polymers that enhance performance while remaining cost effective.