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There is limited information on the characteristics and performance of paving mixtures made with 100% bio-binders. Moisture damage resistance of this type of mixture is a concern since the components of the bio-binder may have a higher affinity with water than asphalt binders. In this context, this paper presents a moisture damage susceptibility evaluation of wood-based bio-binder-aggregate interfaces in terms of energy parameters calculated from surface free energy components. The bio-binder was used as a total replacement for asphalt binders, and the responses were compared to a neat- and a highly modified-asphalt binder, considering different aggregate sources. Results suggest the bio-binder has similar moisture damage resistance to the neat asphalt binder and higher resistance than the highly modified asphalt binder, providing a first indication for the potential use of this bio-binder as 100% asphalt binder replacement. However, additional research is still required to validate these findings at the mixture level. [ABSTRACT FROM AUTHOR]

This study explores different methodologies to select proper doses of three palm-oil-based rejuvenators to restore the properties of the effective binder present in asphalt mixtures with high Reclaimed Asphalt Pavement (RAP) content. Two commercial vegetable-based rejuvenators were also used as reference for comparison. The dose selection methods are based on penetration and softening point in unaged, short- and long-term aged states, and High Temperature Superpave Performance Grade (PGH) verified with Fatigue Low-Temperature Superpave Performance Grade (PGFL). In addition, a novel approach based on the thermodynamic properties of the recycled binder blends (i.e. mix of virgin binder, RAP binder and rejuvenator) quantified through the Surface Free Energy (SFE) measurements was also explored. In all cases, the optimum dose selection was determined by the amount of rejuvenator required to provide equivalent or better properties than the virgin binder in its unaged and aged conditions. The results suggest that the PGH approach verified with PGFL is the most appropriate method to determine the optimum rejuvenator dose. This methodology was initially validated by means of rheological and chemical testing conducted on the recycled binder blends at the selected dose in different ageing states. [ABSTRACT FROM AUTHOR]

Stone-on-stone contact of the coarse-aggregate fraction is one of the main characteristics of permeable friction course (PFC) asphalt mixtures that is required to provide adequate resistance to both raveling and permanent deformation. Currently, stone-on-stone contact is determined by comparing the air voids content in the coarse aggregate (VCA), assessed in both the dry-rodded condition ([VCA.sub.DRC]) and the compacted PFC mixture ([VCA.sub.mix]). The underlying assumption is that the coarse aggregate of a compacted PFC mixture with [VCA.sub.mix] equal to [VCA.sub.DRC] would develop a stone-on-stone contact condition equivalent to that existing in the dry-rodded aggregate. This study focused on proposing enhancements for the quantitative determination of stone-on-stone contact of PFC mixtures. The assessment supported on both laboratory testing and application of the discrete element method and image analysis techniques, led to recommendation of a criterion to determine the breaking-sieve size. In addition, verification of stone-on-stone contact using a maximum VCA ratio of 0.9 was recommended to ensure the design and construction of PFC mixtures with fully developed stone-on- stone contact. DOI: 10.1061/(ASCE)MT.1943-5533.0000117 CE Database subject headings: Asphalt pavements; Porous media; Aggregates; Mixtures. Author keywords: Asphalt pavements; Porous pavements; Asphalts; Aggregates.

Drainability is one of the main characteristics of permeable friction course (PFC) mixtures and is the primary reason for using these mixtures as the surface course in asphalt pavements in the United States. Current approaches suggested for PFC mix design to evaluate drainability (using gyratory-compacted specimens) include: (1) achieving a target total air void (AV) content as an indirect indication of permeability and (2) direct measurement of permeability in the laboratory. The assessment conducted in this study suggested that these approaches are not effective in ensuring adequate drainability in field-compacted mixtures. Thus, different alternatives were evaluated to improve this assessment. Corresponding analysis suggested that: (1) the water-accessible AV content can be used as a surrogate of the total AV content to indirectly assess permeability and (2) the water flow value (outflow time) can be applied to evaluate the field drainability of PFC mixtures. The expected value of permeability, determined using a modified version of the Kozeny-Carman equation, was recommended to analytically predict permeability for mix design and evaluation purposes. DOI: 10.1061/(ASCE)MT.1943-5533.0000053 CE Database subject headings: Asphalt pavements; Porous media; Permeability; X-rays; Asphalts; Mixture; Friction. Author keywords: Asphalt pavements; Porous pavements; Permeability; X-rays; Asphalts.

Laboratory evaluation of unbound granular materials response (e.g., paving granular subbases and bases), subjected to dynamic load is limited in Colombia. This state of the practice is related, among other aspects, to the fact that the dynamic triaxial equipment required for its determination is expensive, and the test protocols are complex. In the last decade, work has been carried out to develop the dynamic CBR test (dCBR) that employs the CBR equipment but modifies the testing protocol applied in the CBR test. This research proposes the basis of a new protocol for the dCBR test to determine the stiffness of granular materials (i.e., equivalent resilient modulus) by applying seven steps repeated load, where each step is defined by a target strain. The study included two marginal granular materials (MGMs) with high plasticity indexes. The results suggest that the proposed dCBR test protocol allows for estimating the equivalent resilient modulus. In addition, the proposed protocol differentiates the effect of the plasticity index on the stiffness of the MGM (i.e., reduction of equivalent resilient modulus as the plasticity index increases). Therefore, we propose to extend the range of materials characterized to validate the preliminary results presented and inquire about a possible correlation between the values of resilient modulus and equivalent resilient modulus. [ABSTRACT FROM AUTHOR]