As Dr. Hamidreza Sahebzamani – Technical Services Manager, SAMI Bitumen Technologies writes, both the company and the industry has thrived off more than 100 years experience in bitumen emulsions.
The road industry has come a long way since the days of informal and dusty pathways. Today, we witness an intricate network of highways, byways, and city streets that connect communities, facilitate trade, and enable the movement of goods and people. Behind this impressive growth lies a key ingredient that has played a pivotal role in the longevity and performance of surfaced roads: bitumen emulsion.
Determining the exact date and inventor of an industrial product or technological process can be challenging. The same applies to bitumen emulsions and their history. Initially, tars were commonly used as road binders, with the first paving taking place in 1854 in Sallinis, Auch, France. However, the origins of the first “direct emulsion” of bitumen in water are less certain. Experiments with mixing “heavy crude oils” or “naphtha oils” with water began in the early 20th century. Around 1903, a “heavy crude oil emulsified and saponified by ammoniacal water” was applied in Beaulieu-sur-Mer, France.
Additionally, in 1904, “emulsified crude oil” was used on the Ardennes car racing circuit to prevent accidents caused by racing cars. Although early patents mainly focused on oil emulsions with higher water content and less bitumen.
It was in 1923 that Hugh Alan McKay, an English chemist working for Shell, introduced the modern formulation of bitumen emulsion, consisting of 70 per cent bitumen and 30 per cent water, which closely resembles the mixtures used in present-day road construction and we may consider it as the birth of modern bitumen emulsion. His invention went on to become what is known as COLAS (COLd ASphalt) which was the brand name given to bitumen emulsion by Shell.
The adoption of bitumen emulsion gained momentum quickly. In France alone, around a hundred tonnes of emulsion were used in 1923. The following years witnessed a substantial increase, with consumption reaching 2500 tonnes in 1924 and 6000 tonnes in 1925. Internationally, the combined production of bitumen emulsion in countries like England, Germany, Denmark, Australia, and India exceeded 150,000 tonnes by the end of 1926.
A significant advancement in bitumen emulsion occurred in 1951 with the introduction of cationic bitumen emulsions. These cationic emulsions, characterised by their positive charge, gained popularity due to their improved properties and performance. Within just ten years of their introduction, cationic emulsions accounted for 50 per cent of total production in 1962, and this percentage skyrocketed to over 92 per cent by 1971.
The primary advantage of utilising cationic bitumen emulsion instead of anionic emulsions lies in the chemistry of cationic emulsions, enabling them to adhere to both positively charged aggregates like limestone and basalt, as well as negatively charged materials such as silex, quartz, and granite. This level of adhesion is not achievable with anionic emulsions and negatively charged aggregates.
Bitumen emulsion in the road industry offers several sustainability advantages over traditional cutback bitumen. One significant aspect is the improved safety it provides. Unlike cutback bitumen, which requires heating to become liquid enough for the application, bitumen emulsion is already in a lower viscosity state at ambient temperatures. This eliminates the need for heating, reducing the risk of fire, explosions, and fatal injuries associated with handling and heating petroleum products.
Furthermore, bitumen emulsion contributes to better health outcomes for workers and surrounding communities. Cutback bitumen contains volatile organic compounds (VOCs) that can be released into the air during application and construction. Prolonged exposure to these VOCs can have detrimental effects on respiratory health and overall well-being. In contrast, bitumen emulsion significantly reduces the emission of volatile compounds, creating a healthier work environment with fewer respiratory risks.
In terms of environmental benefits, bitumen emulsion offers advantages in reducing carbon footprint and minimising environmental pollution. Cutback bitumen relies on petroleum distillates and solvents derived from fossil fuels, contributing to greenhouse gas emissions and climate change. The production and application of cutback bitumen also pose the risk of soil and groundwater contamination due to the leaching of solvents.
Bitumen emulsion, on the other hand, has a lower carbon footprint as it consumes less energy during production and relies on water as a carrier. The reduced solvent content in bitumen emulsion minimises the risk of environmental pollution, preserving ecosystems and water quality.
Australia boasts the largest road network per capita globally, spanning over 870,000 kilometres, making it an extensive network. Approximately 40 per cent of this network is paved using various bituminous products. These road surfaces typically involve essential applications such as prime coats, initial seals, SAMI seals, and spray seals. However, it is unfortunate that a significant quantity of cutback products is still utilised in these applications in Australia.
In mentioned applications, cutback products are employed for precoating aggregates, providing a penetrating coat to base courses, and reducing the viscosity of bitumen or modified binders prior to spraying. Remarkably, the road industry in Australia consumes a staggering amount of approximately 12,000 tonnes of kerosene and 15,000 tonnes of diesel each year in the production process, excluding the fuels themselves.
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This significant quantity could be greatly reduced by replacing cutbacks with bitumen emulsions, resulting in an annual decrease of approximately 12,300 tonnes of CO2e emissions according to the AfPA LCA calculator.
The use of cutback bitumen has been prohibited in numerous countries, including the USA and Europe for decades. Australia remains one of the largest consumers of cutback products globally, despite being one of the pioneering countries to adopt bitumen emulsion approximately 100 years ago. Regardless of the underlying reasons, the current outcome is undesirable, emphasizing the need for a change in mindset.
By embracing the utilisation of bitumen emulsion, road construction projects showcase their dedication to sustainability and environmental stewardship. This decision not only reduces the risk of accidents and health hazards but also enhances the overall well-being of workers, neighbouring communities, and the environment.
Bitumen emulsion offers a safer and healthier alternative to cutback bitumen, all while maintaining the necessary technical requirements. This choice ensures the durability and sustainability of road infrastructure while mitigating the impact on both human health and the environment.
Bitumen emulsions play a crucial role in various aspects of flexible or composite pavement construction, maintenance, and preservation. They find application in multiple layers of the pavement, offering a wide range of benefits. From the base layers, where emulsions (ETB) can be used to treat base courses, to surface layers where structural cold wearing courses known as grave emulsions can be applied.
Emulsions serve as penetrating prime coats, primer seals, and tack coats with high shear strength. They can be sprayed as fog seals, rejuvenating/enrichment seals, or scrub seals to extend the lifespan of aged surfaces and effectively seal them to prevent water penetration. Additionally, emulsions are employed in various maintenance applications such as spray seals, slurry seals, microsurfacings, cape seals, otta seals, graded seals, seal coats, etc. They can even be used in thin layer surfaces like bonded wearing courses or as storable/packaged cold mixed materials for filling potholes or as cold materials in crack sealings/fillings.
The use of bitumen emulsion in the world has always been growing due to the expansion of road construction and maintenance activities, as well as its substitution for cutback products and conventional hot applications. According to the key figures from IBEF, in 2019, the global consumption of bitumen emulsion amounted to 8.6 million tonnes, accounting for 7.8 per cent of the total global bitumen consumption. However, in Oceania, this ratio stood at only 1.8 per cent, making it the lowest in the world.
Bitumen emulsions provide a plethora of opportunities to the road industry, enabling versatile and effective solutions. However, successful utilisation of bitumen emulsion requires a deep understanding of manufacturing and formulation engineering, precise selection of chemicals and raw materials, and the establishment of the appropriate production processes. The knowledge and expertise in these areas are critical as they can make the difference between a successful application and potential challenges when working with bitumen emulsion.
As we celebrate 100 years since the advent of modern bitumen emulsions, it is crucial to acknowledge their significant role in improving road infrastructure. Bitumen emulsion has revolutionised the road industry, transforming road design, construction, and maintenance. It brings advantages such as durability, sustainability, safety, and better performance. As research and innovation continue, bitumen emulsion is expected to further improve, expanding its applications and contributing to the development of resilient and eco-friendly road networks.
Looking ahead, bitumen emulsion will continue to shape the road industry, offering cost-effective solutions and contributing to the advancement of sustainable road construction and maintenance practices. With its ongoing development, we can expect even more efficient and environmentally friendly roads in the future.
SAMI Bitumen Technologies has been a pioneer in bitumen emulsion innovations and production for nearly half a century. SAMI offers a range of unique products tailored for various applications. Two well-known emulsion primes from SAMI are SAMIprime K2 and K2P, which are commonly used as prime coats for granular, stabilised, and concrete base layers.
SAMIBioPrime is a fast-penetrating prime coat formulated with 100 per cent petroleum solvent-free ingredients, aiming to achieve a carbon-neutral product. For superior bonding without tracking issues, SAMIbond 007 is a non-tracking polymer-modified tack coat that provides high shear strength to adhere asphaltic layers to underlying surfaces without sticking to construction vehicle tires.
SAMIfloat is a polymer-modified cationic high float emulsion, specifically designed for exceptional performance in cold seasons and suboptimal aggregate conditions during spray sealing applications.
SAMIflex encompasses a range of high-performance polymer-modified emulsions suitable for spray sealing and Stress Alleviating Membrane Interlayers. Additionally, Colmat emulsions are formulated to ensure the durability and workability of microsurfacing applications in all seasons, with minimal downtime before opening to traffic.
These examples exemplify SAMI’s commitment to research, development, and promotion of bitumen emulsion within our industry, bridging the gap between our country and global standards.
1. Bitumen emulsion, 2008, USIRF (French Union of Road Industry Associations)
2. MS-19, Basic of Asphalt Emulsions, Asphalt institute
This article was originally published in the August edition of our magazine. To read the magazine, click here.