Investigation on performance characteristics of dense graded hot mix asphalt with RAP and Crumb Rubber

The use of recycled materials in asphalt mixtures such as reclaimed asphalt pavements (RAP) have become widely accepted as a replacement for virgin asphalt binder or virgin aggregates. In this study, the RAP content was 30%, and CR additives were blended with the soft unmodified binder by using dry processes. The objective of this study was to investigate and evaluate the engineering properties of dry method application of crumb rubber influences on reclaimed asphalt pavement (RAP) mixtures. To evaluate the effect of rubber-bitumen interaction on the mixture’s mechanical properties, a laboratory investigation has been conducted on a range of dense graded and 30% RAP by dry process crumb rubber modified (CRM) asphalt mixtures containing 0% (control), 1% crumb rubber by the total aggregate mass. The experimental program in this research include the binder extraction for estimating the amount of aged binder in the both fine and coarse RAP material. Before extracting the binder the RAP sieve analysis, have been done to provide the Black grading curve. In continue after the binder extraction the material sieved again to providing the white curve. The comparison of Black and White curve indicated that there is a remarkable difference between the aggregate grading even for the fine RAP. The experimental program was continued by fabricating 12 specimens in different 4 types of mixtures. For the first group no RAP, no rejuvenator and no crumb rubber were used. For the second group 30% of virgin aggregates substituted by RAP material and the third group was similar to the second group just with 0.01% rejuvenator. the forth group was the group, which in that the specimens contain RAP, rejuvenator and crumb rubber. Finally the specimens were tested for Indirect tensile strength. The results indicated that the addition of crumb rubber increased the optimum amount of binder in the mixture with 30% RAP.

Rheological Characterization of Bitumen and Asphalt including the effect of Added-recycled Material

This thesis evaluates the rheological behaviour of asphalt mixtures and the corresponding extracted binders from the mixtures containing different amounts of Reclaimed Asphalt (RA). Generally, the use of RA is limited to certain amounts. The study materials are Stone Mastic Asphalts including a control sample with 0% RA, and other samples with RA rates of 30%, 60% and 100%. Another set of studied mixtures are Asphalt Concretes (AC) types with again a control mix having 0% RA rate and the other mixtures designs containing 30%, 60% and 90% of reclaimed asphalt which also contain additives. In addition to the bitumen samples extracted from asphalt mixes, there are bitumen samples directly extracted from the original RA. To characterize the viscoelastic behaviour of the binders, Dynamic Shear Rheometer (DSR) tests were conducted on bitumen specimens. The resulting influence of the RA content in the bituminous binders are illustrated through master curves, black diagrams and Cole-Cole plots with regressing these experimental data by the application of the analogical 2S2P1D and the analytical CA model. The advantage of the CA model is in its limited number of parameters and thus is a simple model to use. The 2S2P1D model is an analogical rheological model for the prediction of the linear viscoelastic properties of both asphalt binders and mixtures. In order to study the influence of RA on mixtures, the Indirect Tensile Test (ITT) has been conducted. The master curves of different mixture samples are evaluated by regressing the test data points to a sigmoidal function and subsequently by comparing the master curves, the influence of RA materials is studied. The thesis also focusses on the applicability and also differences of CA model and 2S2P1D model for bitumen samples and the sigmoid function for the mixtures and presents the influence of the RA rate on the investigated model parameters.