EBE Technology Warm Conglomerates
Traditional technology involves the asphalt conglomerate being prepared hot (HMA Hot Mix Asphalt): the asphalt in liquid state (at about150-170°C) is mixed with the aggregate to obtain the ideal covering of the inert material. To bring about this process with the best possible results, the aggregate must be raised to a temperature of about 150-160°C in a rotary drum kiln, defined as dryer, which must first eliminate the humidity in the aggregate then heat it to the required mixing temperature.
Low Energy Asphalt – LEA®
New technology makes it possible to produce conglomerates at less than 100°C with a saving in the energy input for the process in the order of 40%. These “Warm” conglomerates (WMA Warm Mix Asphalt) can be produced using different procedures, but that which is undoubtedly giving the best results is the system devised by the French company LEA-CO, one of the pioneers in research on road building technology.
The procedure known as LEA® (Low Energy Asphalt) or EBE (Enrobage à Basse Energie) is based on the use of wet sand. The logic behind the process is that the energy required to transform water into steam is five times higher than that needed to heat aggregate from 0°C to 100°C; furthermore, fine aggregates like sand tend to have a higher humidity content, so if drying the sand can be avoided the energy saving may be more than 40%.
The procedure is as follows:
- larger gauge aggregate is dried and heated to about 150-160°C;
- liquid state asphalt, before it is injected into the mixer, has a special additive put into it;
- the asphalt and the large aggregate are mixed at high temperature (150-160°C);
- wet sand at air-temperature is added to this mixture (if it is not sufficiently damp it can be sprayed with water);
- when the high-temperature mix (large aggregate and asphalt) comes into contact with the damp sand, the water content is transformed into steam, which expands to create the effect of “foaming” the asphalt which thus spreads and covers the granules of fine aggregate;
- the fine aggregate, in contact with the larger gauge, is heated up and takes the mixture to an equilibrium temperature of less than 100°C;
- the residual water content re-condenses inside the mixture in small droplets which help to keep a good working consistency in the conglomerate, even at low temperature.
The whole process, which includes the recycling of milling material (RAP), is possible thanks to a series of specifically dedicated technological components and is controlled using a specialist software.
The use of Tiepido WMA conglomerate brings a series of advantages:
- reduction in energy consumption with consequent reduction in pollution (from certified tests carried out in France, the emission reduction is 55%)
- absence of smoke and smells during production and pouring;
- better working conditions for the workforce in the latter case, considering the lower temperature of the material;
- possibility of working further away from the production base thanks to the lower heat dispersion and good workability of the material at lower temperature;
- possibility of operating in a lower temperature environment, not suitable for traditional conglomerates;
- reduction in the time need before reopening the roads to traffic after asphalting.
Summing up, the adoption of LEA® technology allows S.A.M. to apply the principles it believes in of safeguarding the environment, translating them into two important practical aspects:
- he reduction in energy consumption in the production cycle with consequent reduced air pollution due to lower fuel consumption,
- recycling of milling material (RAP Reclaimed Asphalt Pavement) giving appreciated value to exhausted material, milling waste, with consequent reduction in demand for newly quarried aggregate.