Technique Developed to Lay Asphalt without Heating Bitumen

Bitumen is used in traditional asphalting, a sub-product that remains after successive oil refining, and dry goods, stones that confer stiffness on roads. Bitumen acts as adhesive but, as it is a very viscous material, it has to be heated to be used. Since some years ago, big technological innovations have been introduced to carry out the cold process, using the so-called bituminous emulsions, heterogeneous systems composed of two stages or elements, insoluble of each other, usually bitumen and water.

Researchers of the group ‘Physics of fluids and biocolloids’ of the University of Granada, have worked with a system in which bitumen emulsifies at room temperature through a tensioactive or soap, forming small drops that make the system more fluid, which facilitates transport and allows cold application. “As we do not need to heat bitumen we save energy, reduce environmental pollution and improve work conditions”, explains Roque Hidalgo, Professor of Physics and one of the researchers who have taken part in the project.

Burst time

The study contributed a better control of the aggregation state of the system to the industrial experience with cold bituminous emulsions. This is a key point in the process: to be useful, it is necessary to control in which circumstances the emulsion will be stable, making possible to transport it and work with it, and under which circumstances it will stop being stable. It only should happen when it is mixed with dry goods, a moment in which the emulsion “breaks” and bitumen and the soapy substance separate, allowing the first to act as adhesive of the solids.

The break stage of the emulsion is essential for the quality of asphalt. The researchers of the UGR [http://www.ugr.es] have developed a technology that allows to measure and control how long the process is, and they have tested it in almost real conditions using several types of emulsions and bitumen. The system has been developed through an agreement with Repsol YPF that finished in 2004. This collaboration has remained for seven years, “an exceptional situation when it is about agreements with the industry”, says Hidalgo.

The research group he works with, founded by him in the in the eighties, gathers a wide experience in projects which can be implemented in business world, and for this reason it was awarded the First Prize of the Social Council of the University of Granada. “Our group carries out research works with industrial implementation and, occasionally, it counts on the support of companies to carry them out”, says the UGR Professor. The researcher in charge of the project was the Professor of Physics Miguel Cabrerizo.

Daily colloids

One of its most tested research lines, which has generated collaborations with other companies, is the Physics of Colloids. Colloid means “glue”, adhesive, and the field of study comprises the systems in which there are two phases or elements; for example, a solid –sized between a micron and a nanometre-, and a liquid. The implementations Colloidal Physics seem to be inexhaustible: for example milk is a colloid; and so are paints, blood, adhesives, soft drinks, …

Its application in the field of asphalts contextualizes in construction sector, which is the main motor of the economy of the country. According to the Spanish Road Association, during the nineties public administration invested €30 billion in the construction or improvement of the roads. An example: Spain was in that period the country of the EU where more motorway kilometres were built - 3,600 -. Andalusia was the autonomous region which received more state funding - €2.756 billion -, and the second in local investment - €1.743 billion -.

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