Investigation of the Usability of Foamed Bituminous Mixtures as Bituminous Base Course

Materials recycled with foam bitumen are promising materials for pavements economically and environmentally. However, there are different opinions in the literature about how these materials are positioned in the pavement. It is clear that their performances will not be suitable for the wearing course, but that they are used for the plant mixture base course because they contain bitumen, and that these materials will be neglected in the evaluation of these materials. In the study, 4 different foam bituminous mixes prepared with a recycled pavement material and a standard bituminous base course mix were compared in terms of the resilient modulus obtained from the uniaxial indirect tensile resilient modulus test. Gradation is the same for three of the mixtures, two of them use cement as a mineral binder, but 70/100 grade bitumen in one of these two productions and 50/70 grade bitumen in the other. In the third mixture, 70/100 grade bitumen and hydrated lime (HL)+fly ash (FA) were used. In the final mixture, 70/100 grade bitumen and cement were used as mineral binders, but gradation was changed. In addition, permanent deformation control for the final production was carried out with a triaxial cyclic compression test. It was concluded that all these variables affect the results, but the resilience modulus values obtained for all were quite close to those obtained from the bituminous base sample. Considering that the foamed bituminous mixtures will be thicker than the bituminous base course in practice, it is considered structurally appropriate to use this layer instead of the bituminous base course.