Effect of Process Parameters on Foam Bitumen-based Road Material Production at Ambient Temperature

The production by batch cold-mix technique of foam bitumen-based bound graded aggregates is studied at laboratory scale. The influence of some mixing parameters (mixing system, mixing time, shaft speed, aggregates temperature and foam characteristics) and bitumen content is analyzed. An original developed test permits a measure of the mixture microstructure. A twin-shaft mixer gives better results than a planetary mixer. The mixture temperature during mixing, resulting from aggregates and foam temperatures, seems being the most influent mixing parameter. It favours the dispersion of bitumen in smaller particles of mastic. It is shown that cohesion of compacted material, measured by direct compression test, is highly dependent on the grading of mastic particle before compaction.