Investigation of the effect of mineral fibers on the performance of recovered asphalt mixture

Using recycled materials in asphalt mixtures not only ensures the sustainability of natural resources, but also offers positive economic and environmental benefits. Asphalt pavements, which are completely recyclable, are used on average around 10%-30% in hot recovery because of aging of the bitumen and breaking of the aggregates during the construction phase and service life. If the recycled asphalt coating rate used in the mixture is not more than 25%, there is no significant change in the performance of the mixture, even a better performance was observed in permanent deformations. 12 different mixture designs were prepared by adding 0%, 0.1% and 0.3% basalt fiber of total aggregate weight to asphalt mixtures containing 0%, 15%, 30% and 45% reclaimed asphalt pavement (RAP). Superpave volumetric mix design method was used. RAP bitumen modified with high penetration virgin bitumen and no rejuvenator was used. The modified Lottman test was applied to measure the moisture sensitivity and indirect tensile strength of the prepared mixtures, and the Hamburg rutting test was applied to measure the resistance to permanent deformation. As a result of the modified Lottman test, it was observed that the tensile strength of the mixture increased as the RAP ratio increased. At the same time, the increase in basalt fiber ratio also increased the tensile strength of the mixture. The highest tensile strength was observed in the mixture containing 30% RAP and 0.3% basalt fiber. All tensile strength ratios (TSR) provide the minimum 80% TSR value required by the specification. The Hamburg rutting test was applied to measure rutting performance. The Hamburg rutting test was applied to the mixture that gave the best results in each RAP group in the TSR test. According to the rutting test results, as the RAP content in the mixture increased, the resistance to permanent deformation also increased. The lowest rut depth was obtained in the sample containing 45% RAP and 0.3% basalt fiber. It was concluded that the use of RAP in hot mix asphalts does not have a negative effect on pavement performance, on the contrary, it has a positive effect in terms of moisture sensitivity and rutting. It is thought that the RAP rate, which is stated as 25% in the Highway Technical Specifications, can be increased to higher levels without a decrease in pavement performance by strengthening it with basalt fibers. KEYWORDS: reclaimed asphalt pavement, Superpave, indirect tensile strength, Hamburg rutting test