Bitumen emulsion for road construction

Road top degrades during operation sue to two groups of factors: mechanical and climatic. Mechanical damage is caused by fatigue of the road top due to transportation load, made worse by uneven surface. This happens, for instance, when heavy trucks (30 tons and above) pass along the road in summer in temperatures in excess of 30ºС.

Climatic factors influence the asphalt due to poor quality of the binder (bitumen) and/or due to sharp changes of bitumen properties during production of bitumen-mineral mix.

The former case is mostly cause by inadequacy of bitumen or polymer-modified bitumen properties. For instance, traction on glass can somewhat characterize adhesion properties of bitumen. It can be determined but not regulated: the important thing is to determine bitumen viscosity and the content of paraffin and cohesion of bitumen-polymer material.

Sharp changes in bitumen characteristics during production of road top is caused by oxidation of bitumen in traditional hot process, which increases the rate of its aging.

Aging of bitumen in a road top under the influence of oxygen, elevated temperature, moisture and catalytic minerals occurs in four stages: strengthening of the structure, stabilization, beginning of destructive processes and destruction. An accelerated transition from the first two to the last two due to heating of bitumen during mixing with mineral material occurs due to two key factors.

First, bitumen heating causes local or general overheats. Regardless of mix composition and bitumen quality, the aging processes accelerate sharply above 160 °С.

Second, the rate of aging depends on the way bitumen was heated: in volume or in film covering mineral particles. Film bitumen in asphalt-concrete ages faster  with all other conditions equal. Today, bitumen plants use collection tanks to store ready asphalt mix from one shift to several days at high temperature. The rate of aging of the film layer during storage and transportation at elevated temperature significantly accelerates aging during operation. In such conditions aging is so quick that bitumen increases consistency by the hour. In the result, the mix contains bitumen with lower penetration and viscosity and higher softening point than originally intended. This is one of the most important causes for reduction of road top service duration.

Reduction of influence on asphalt concrete of the above mechanical and climatic factors can be achieved by changing the regulations defining the consist and quality of the material and the binder. Reduction of bitumen aging rate in operation conditions can be achieved by changing of bitumen-mineral mix production technology.

There are two alternative approaches to reduction of bitumen viscosity to the point where it can be efficiently mixed with mineral filling material: using solvents and the use of bitumen emulsions. The former method increase the cost of bitumen products and causes significant damage to the environment by releasing vapors of organic solvents.

The emulsion base technology of bitumen based road top has become wide spread in recent decades. Beside reducing the bitumen’s aging rate, using emulsions has other advantages (less energy consumption, ability to lay the road top on wet surface etc) over the traditional hot technology.

The amount of asphalt mix based on bitumen emulsion increases. In 2006 over 30% of all binding materials in France were emulsified.

It is necessary that the consist and method of emulsion preparation ensure the required viscosity and stability in transportation and storage, with relatively low cost of raw material. The component which influences the above parameters the most is the emulsifier.

The components used for the production of bitumen emulsion and the production process is mainly defined by the process equipment.

Among the currently available plants for production of cationic or anionic emulsions, the UVB-1 plant by GlobeCore is one of the most efficient. By choosing the model of the required production capacity, the client can optimize the process of bitumen emulsion production at the facility with guaranteed production of the required quantity and quality of the product.

обновлено: December 19, 2014 автором: globecore