Granular materials treated with gravel-cement type hydraulic conglomerates or the like, are commonly used as a base layer in many countries. They offer good structural capacity but some crack-related problems as well. Gravel treated with cold- or hot-mix bituminous binders are also quite common given their flexibility and ability to adapt to any type of traffic conditions, although they do display some plastic deformations and a temperature-dependent mechanical performance. This presentation proposes an alternative that combines the advantages of each technique through the simultaneous use of hydraulic conglomerates and bituminous binders. This implies the use of bituminous emulsions, since water is essential for the development of hydraulic conglomerates. The mechanical performance of three types of granular materials with different combinations of cement and emulsion was analysed. These granular materials correspond to two natural soil types A-2-6 and A-2-4 and fully crushed reconstituted gravel. The study was carried out according to Spanish criteria for the gravel-emulsion design. However, some of the results obtained indicated the need to study another type of approach. The Spanish criterion for the gravel-cement design was also followed, but was not entirely satisfactory either. The first conclusion of the study was the convenience of developing criteria designs specifically for these mixed mixtures. The combined effect of cement and emulsion on materials with quality plastics (types A and B) yields acceptable results with relatively high contents of cement and emulsion, which is not very economical. Good mechanical results are obtained with good quality materials. However, the mechanical behaviour differs depending on the relative proportions of cement and emulsion. (A)
Abstract