Cold mix technology in the spotlight

New, advanced analysis methods to study the interaction between bitumen emulsions and mineral surfaces provide an important contribution to achieving sustainability benefits.

At the turn of the year, a multiyear research project was launched in a collaboration between Luleå University, the construction company Peab and Nynas. The objective of the collaboration is to develop new test methods to facilitate the choice of bitumen and aggregate material when designing high-performance cold mix asphalt. The project will be run over three years and is being funded by Formas, a Swedish government research council for sustainable development.

“The intention is to acquire a fundamental understanding of the major parameters that influence breaking, coalescence and structure build up in relation to mineralogy and surface characteristics of the aggregate material in cold asphalt mixtures,” says Dr Hilde Soenen, Nynas Bitumen Research Manager.

The starting point is to investigate how different types of minerals, in the first instance feldspar, plagioclase and quartz, affect the rate at which an emulsion breaks.

“This will allow us to identify the parameters to optimise emulsion behaviour for different types of minerals during various stages of cold mix asphalt production,” explains Hilde Soenen.

With a better understanding of the breaking and curing of emulsions as a function of the aggregate mineralogy, it is possible to avoid emulsions breaking too early or too late. The project will also evaluate the possibilities of using ultrasound in the formation and breaking of emulsions.

Nynas role in an initial phase is to prepare emulsions with specific properties, while Luleå University is contributing its expertise in the fields of NMR* and ultrasound technology.

“Much of the work takes place in the laboratory,” continues Hilde Soenen.

“Once we have the results in place, Peab and Nynas will conduct a bigger pilot test at a trial facility, probably in 2024.”

In its examination of the project, Formas acknowledges the very high level of scientific expertise in the participating parties, and the fact that there are good opportunities to achieve significant results when it comes to using cold mix asphalt on major roads. Also emphasised is the sustainability benefits from significantly lower energy consumption and CO2 emissions.

*Nuclear Magnetic Resonance spectroscopy (NMR) is a quantitative method that provides information about the structure of molecules and molecular interactions.

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