This invention relates to bituminous paving composition and,more particularly , to bituminous paving compositions ehich ,in admixture with paving aggregates,can be formed into dense,stable pavement by application of pressure but withot the application of heat.
The adhesive qualities of bituminous materials, coupled with their wear charecteristics, commend these materials for the construction of road surfaces can be constructed utilizing heat-liquefied high penetration bituminous materials and aggregate, the sometimes more economically attractive cold-laying methods utilizing delayed amalgamation of a powdered bitumen and liquid bitumen have presented a number of difficult problems.
Since economy dictates that the ston aggregate and bituminous binder be premixed at a plant in bulk quantities and requisite amounts of cold-laid paving materials be shipped to the individual job site for use at the appropriate time , cold-laid paving materials must be capble of retaining their workability for considerable storage periods regardless of seasonal temperature changes encountered, such as relatively high summer storage temperatures. The aggregate and associated binder must not coalesce into an unworkable mass with an increase in ambient temperature, nor may the aggregate and binder be converted to granule to granulrs wich are incapable of being compacted into a stable pavement because the weather turns ccold.
While a retarded amalgamation rate is essential to insure extended stockpiling, once the pavement is formed the retarded amalgamation rate of the powdered bitumen can become a troublesome handicap. Since the powdered bitumen in the newly formed pavement is not amalgamated, the binder of the pavement has not attained its ultimate hardness and stability. Yet the pavement must exhibit immediate i.e. early, stability even when elevated pavment temperatures are experienced due to solar radiation. Inasmuch as increasing temperatures decrease the viscosity of the fluid portion of the binder, elevated temperatures aggravate further the problem of achieving immediate pavement stability.