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.

Full-depth reclamation (FDR) is the technique of in-place recycling of the asphalt-bound layer of a pavement along with part of the underlying unbound layer to produce an improved base material. The objective was to develop a mix design system for FDR and evaluate the performance of designed reclaimed materials from the western part of Maine. Mixes were prepared in the laboratory, and samples were compacted with the Superpave® gyratory compactor. The samples were then tested for bulk specific gravity and resilient modulus. Samples of mixes prepared with asphalt emulsion, water, emulsion plus lime, emulsion plus cement, and emulsion plus lime and cement were also tested for their resilient moduli at different cure times and for their shear strengths. Rut tests were also conducted with the samples under water to evaluate the stripping potentials of the different mixes. The test results showed that maximum density and resilient modulus criteria can be used to select the optimum additive content for water and asphalt emulsion mixes. Comparison of performance testing results showed that mixes with additives develop strength faster and show significantly higher shear strength and stripping resistance than mixes with water only. For the materials tested, addition of lime and cement with asphalt emulsion appears to increase the rate of gain in strength and, hence, to result in faster curing and to increase the shear strength as well as resistance against moisture damage. It is recommended that FDR sections with asphalt emulsion, lime, and cement be constructed and evaluated for in-place performance.

About 20,000 tons of manufactured waste asphalt shingles are being deposited in landfill every year in the state of Massachusetts. This has caused a shortage of precious landfill space, and significant increase in deposit fee. There is a need to evaluate the use of these waste shingles in hot mix asphalt, specially because the shingles contain significant amount of asphalt binder, and studies in some states have shown that use of shingles can result in savings, and improve hot mix asphalt performance. A laboratory study was conducted by the Worcester Polytechnic Institute and University of Massachusetts at Dartmouth, with a research grant from the Chelsea Center for Recycling and Economic Development. The results show that volumetric and low temperature property of hot mix asphalt with 3, 5 and 7 percent shingles are not significantly different from the properties of conventional hot mix asphalt used for surface courses. Standard deviation of test results for mixes with shingles are low, indicating consistency in the quality of the shingles. Mixes with 5 and 7 % shingles show significantly lower rutting potential compared to mix without any shingles. Hence, it seems that mixes with small amounts of shingles have the potential of savings as well as good performance. However, before any material can be used regularly, it must be evaluated under real-life production and construction conditions.