Process for the manufacture of a bitumen-aggregate mix suitable for road pavement

Process for the manufacture of a bitumen 105/25-aggregate mix suitable for road pavement

The present invention relates to an aqueous quick-setting bitumen-aggregate mix suitable for cold pavement of roads, parking places, sidewalks and the like. The bitumen-aggregate mix is manufactured by mixing a mineral aggregate, water, a de-emulsifier, containing hydraulic cement, and a cationic oil-in-water bitumen emulsion, containing, as a to emulsifier, a salt of a tertiary diamine and a phosphoric acid.
It is well-known in the art to prepare cationic oil-in-water emulsions of bitumen 105/25 and to mix these emulsions with inorganic mineral aggregates. When mineral aggregates and the cationic emulsion are mixed, the emulsion will “break” due to the attraction between the positively charged bitumen droplets and negatively charged aggregate surfaces. The cationic bitumen droplets will deposit on the aggregate surfaces and be bonded to aggregates by the electrostatic action at the interface between the bitumen droplets and the aggregates. As emulsifiers, several salts between acids and amine compounds have been suggested. Frequently, acidified amidoamines, imidazolines, fatty tetraamines and quaternary ammonium compounds and mixtures thereof are used. The acid used is normally hydrochloric acid, but also phosphoric acids and other acids containing one or more acid hydrogen atoms have been used.
When paving, it is today a general practice to use a mobile mixer, which, at the site of the work, continuously mixes the aggregate, water and the emulsion for obtaining an aqueous bitumen-aggregate mix and continuously spreads the aqueous bitumen-aggregate mix on the surface to be paved. It is of essential importance that the mix has a suitable consistency for paving but also that there is a rapid build-up of cohesion between the bitumen on one side and the aggregates and the surface covered on the other.
Thus, the US Patent 3 518 101 describes an aqueous asphalt emulsion, which contains, as an emulsifier, a salt of a polybasic acid selected from the group consisting of oxalic acid, tartaric acid and citric acid, with a diamine containing an alkyl group from about l2 to about 22 carbon atoms. The amine groups could be primary, secondary and/or tertiary. However, the setting and the build-up of cohesion of the emulsion-aggregate mixes described in this patent are slow and vary also with the types of aggregates and the particle size of the aggregates. The US patent 5 073 297 discloses an aqueous bitumenous emulsion-aggregate obtained by emulsifying bitumen in water with a particular cationic emulsifier, which is a reaction product between modified polyamines with certain polycarboxylic acids and anhydrides.

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