The use of reclaimed asphalt pavement (RAP) helps save natural resources and money. The percentage of RAP that can be utilized successfully in hot-mix recycling is primarily dictated by practical considerations. To avoid deterioration of the aged binder, RAP should not be exposed to relatively high temperatures. This study investigated the feasibility of using a warm-mix asphalt (WMA) additive, Sasobit H8, in successfully recycling hot-mix asphalt (HMA) with 75% RAP at a lower temperature. A control HMA was prepared with extracted aggregates and PG (performance grade) 64-28 binder at 150°C. Another HMA was produced with PG 52-28 binder at 135°C. Two WMA mixes were prepared with Sasobit H8 at 125°C, one with PG 52-28 and the other with PG 42-42 binder. Samples with design asphalt content were compacted by using 75 gyrations of the Superpave gyratory compactor. Their voids, tensile strength at −10°C, rutting potential at 60°C, and moduli at 0°C, 25°C, and 40°C (at different times) were determined and compared. The moduli samples were subjected to 60°C in between the tests. The results show that it is possible to produce mixes with 75% RAP with similar air voids as virgin mixes at lower than conventional temperatures using 1.5% Sasobit. The addition of a significantly lower grade of binder, PG 42-42, at a rate of 1.5% by weight of mix produced a mix that is most comparable with a virgin mix.

Dense graded hot mix asphalt (:HMA) mixtures are designed to have low permeability to resist excessive penetration of water and avoid durability problems. With the introduction of Superpave mixes, there: is a general concern that the coarse graded mixes are more permeable, at similar void levels, compared to fine graded mixes. However, at present there is a lack of a simple tool for measuring the in-place permeability of asphalt mixes. A simple permeability test was developed to determine the effect of voids and gradation on permeability. The field permeameter was used for testing projects with 9.5 mm, fine and coarse, 12.5 mm coarse, 19 mm coarse, and 25 m coarse graded mixes. Testing of cores taken from location of field testing were also conducted in the laboratory. The results from the in-place permeability tests were found to be consistent with experience with fine and coarse graded mixes. The results indicated that mixes with different gradations and nominal maximum aggregate size have significant increase in permeability at different voids in total mix content. Field testing showed that 25 rnm coarse, 19 mm coarse, 12.5 mm coarse and 9.5 mm coarse mixes show significant increase in permeability at 5, 6, 7 and 8 percent voids in total mix respectively, whereas a 9.5 mm fine mix showed a significant increase in permeability above eight percent voids in total mix. Field permeability of 19 mm and 25 mm coarse graded mixes are significantly higher than laboratory permeability, at similar voids in total mix content, most likely due to presence of horizontal flowpaths and high horizontal permeability. It is recommended that field permeability tests be conducted for all mixes, in order to get the best indication of permeability of these mixes.

No abstract

This study was performed to evaluate the use of heated-reclaimed asphalt pavement materials with emulsion and the use of hot-mix asphalt with wax (Sasobit) as base course materials. Mixes with lower-than-optimum and optimum emulsion content, as well as with heated-reclaimed asphalt pavement material and optimum emulsion content, were made; in addition, mixes with conventional asphalt binder and those with asphalt binder and Sasobit were produced at relatively lower temperatures. These mixes were tested for workability, and all but one were used for preparation of approximately 0.9- × 0.9- × 0.125-m slabs. The rates of densification during the compaction of these slabs were compared. Samples cored from the slabs were tested for stiffness and for dry and retained tensile strengths. The results showed that heating of reclaimed asphalt pavement material can improve the dispersion as well as the densification significantly. The use of asphalt binder was found to improve strength and stiffness, and the use of Sasobit helped to achieve almost similar workabilities and compactibilities at a lower temperature compared with those of hot-mix asphalt with neat asphalt binder. No significant difference was found between the modulus of the Sasobit and hot-mix asphalt samples. The dispersion of asphalt binder seemed to improve with the use of Sasobit at a lower mixing temperature. A field project is recommended for evaluating performance of emulsion mixes with heated reclaimed asphalt pavement materials and asphalt binder mixes with Sasobit.

The full-depth reclamation (FDR) process consists of reclaiming all of an asphalt-bound section along with a predetermined amount of underlying base, with some additive. The objectives of this study were to determine the suitable compactive effort for designing FDR mixes, evaluate the benefits of using different types of additives in terms of improvement of pavement life, and determine suitable structural numbers for pavements recycled with different types of additives. The scope of work for this part of the study consisted of conducting falling-weight deflectometer (FWD) tests, testing an existing pavement before FDR, sampling of materials during FDR, determining the density of in-place material after compaction, compacting of loose mix in the laboratory, determining the density of the compacted samples, conducting FWD testing on the finished pavement, determining the resilient modulus of in-place cores, and analyzing the data to determine the suitable number of gyrations, improvement in pavement life, and structural numbers. It was concluded that samples should be compacted to 50 gyrations during mix design and that a minimum of 98% of density of in-place loose mix samples, compacted to 50 gyrations, should be achieved in the field at the end of compaction. Cost comparison showed that for the options considered in this study, recycling with emulsion (3.4%) and lime (2%) is the most cost-effective option. A visual evaluation of recycled sections after one year showed no significant distress in any section except the one with water as additive, in which a moderate amount of edge cracking was noted.