Sustainable road construction with B2Last®
Are you looking for a sustainable yet high-performance bitumen additive? BASF developed an intelligent and innovative bitumen modification that helps you in significantly reducing bitumen emissions and making roads more durable.
Be it an increasing heavy load traffic or more extreme weather conditions because of climate change – today, road surfaces are subjected to ever-higher stresses. Additives for bitumen play a decisive role in the durability of asphalt. At the same time, occupational health and safety, environmental protection and the reduction of CO2 emissions are of high importance for road construction.
With B2Last®, BASF has developed an innovative bitumen additive that combines both asphalt performance and sustainability: Temperature-reduced paving with a high recycled asphalt content is made possible through the use of B2Last®, while guaranteeing consistent workability. This creates significantly lower bitumen and CO2 emissions, while the asphalt resistance is also increased, thereby extending the life span of the road.
Our solution for sustainable road construction
- Reduced asphalt mix production and laydown temperatures at still high reclaimed asphalt ratios while maintaining asphalt performance and its excellent workability
- Less energy needed for heating bitumen, aggregates and reclaimed asphalt
- Occupational health & safety – less bitumen emissions, B2Last® makes work safer
- Enables high reclaimed asphalt ratios – saving primary resources
- Increased road life time – excellent rutting behavior and fatigue resistance across broad temperature range
Reactive modification of bitumen
B2Last crosslinks bitumen components to form a polymeric network with strong elastic properties and excellent durability and crack resistance across a wide range of temperatures. B2Last is integrated into the polymeric network and is fully consumed during the reactive modification.
The dosage amount for B2Last increases the elasticity and softening point, while the low-temperature behavior remains unchanged. The selection of the virgin bitumen enables the temperature properties to be adapted. This makes it possible to flexibly vary the performance of the binding agent across a wide range.
Temperature-reduced installation through reactive modification
B2Last is homogenized with bitumen during the manufacturing process of asphalt. The flow capability of the binding agent is initially increased through B2Last as a low-viscosity liquid. This enables the manufacturing and processing temperatures of the mixed product to be reduced without negatively affecting the compactability.
Throughout the transport and installation processes, reactive modification causes B2Last and bitumen to form a polymer network. Here, reactive groups in the bitumen components act as anchors for B2Last. In particular bitumen from asphalt granulate (AG) displays a high content of reactive groups, enabling high connectivity of virgin bitumen to recycled bitumen. This guarantees excellent workability of the mixed product, as well as enabling the use of high AG content. Following the complete compacting process and cooling of the asphalt, the reactive modification is complete and the asphalt displays its maximum stability.
The chemistry behind reactive modification
The components in bitumen form an interconnected network following reactive modification. This chemical networking primarily takes place between the contained resin and asphalt components. This is due to the fact that they possess a particularly high content of what are known as functional groups. It is on these groups that B2Last docks during the production and processing of the asphalt.
Interaction with aged bitumen from asphalt granulate (AG)
The bitumen from recycled asphalt granulate displays a high content of asphalts and increased functionality. This aspect also has a positive effect on the reactive modification. B2Last can use this bitumen to establish an especially dense network and also establish good crosslinking of the different bitumen types. The binding agent becomes more homogeneous and allows excellent workability of the produced asphalt mix, even when it contains a high content of recycled asphalt.
In order to assess the sustainability of the bitumen additive B2Last, three aspects must be considered: the economy, ecology and social aspects. Only an efficient additive with a good cost-benefit ratio makes economic sense and can be used permanently and on a larger scale. The ecology, and thus the effects of the additive on the environment and climate, can be evaluated via the CO2 emissions during the production and processing of the asphalt mix and maintenance of the road system. The social aspects take into account the effect of the additive on people. For example, the workplace at the mixing plant and on the construction site can be evaluated here when B2Last is used.
B2Last is an efficient additive that combines the advantages of various conventional products in one in small dosing quantities. In addition, modification directly at the asphalt mixing plant requires little technical effort and does not affect the production capacity of the mixing plant.
The use of B2Last makes processing as a hot asphalt at 140°C possible. This reduces the mix temperature by about 30°C compared to a conventional hot asphalt at 170°C. This reduces the consumption of fuel and CO2 emissions of the mix production by about 10 percent. In addition, the B2Last modification extends the durability of the road system, making fewer rehabilitation measures necessary. This results in a reduction of greenhouse gas emissions by about 50 percent.
B2Last enables asphalt to be produced at temperatures of 140°C, thus reducing the formation of bitumen vapors and aerosols. Measurements on the construction site show a significant reduction in emission levels compared with a reference system processed at approx. 170°C. B2Last can thus make an important contribution to reducing the pollutant loads to which workers are exposed on the construction site.
We value the health and safety of people above all else – in all plant trials, we instruct our customers on safe processing and handling the product. The training is based on legal requirements (GefStoffV) and the information provided by ISOPA (European Diisocyanate and Polyol Producers Association). In summary, however, it can be said that no more safety equipment is required for proper use of B2Last at the asphalt mixing plant than for products already established in the industry. The product emissions are also recorded during the manufacturing and processing steps of B2Last modified mixtures. Here, the numerous measurements in practice confirm that the emissions produced during the manufacturing of modified mixtures with B2Last are significantly below those of the maximum permitted workplace concentrations.
All roads rehabilitated with B2Last are in excellent, technically stable condition.
Alongside several stretches of road in the USA, several kilometers of public roads in Bavaria, North Rhine-Westphalia and in Rhineland-Palatinate have been paved using the product. The modified asphalt impressed everywhere, not just in regard to manufacturing and installation, but also during performance testing thanks to its excellent properties.