Study of the effect of four warm mix asphalt additives on bitumen modified with 15% crumb rubber

Due to a growing concern over global warming, the bituminous mixture industry is making a constant effort to diminish its emissions by reducing manufacturing and installation temperatures without compromising the mechanical properties of the bituminous mixtures. The use of mixtures with tyre rubber has demonstrated that these mixtures can be economical and ecological and that they improve the behaviour of the pavements. However, bituminous mixtures with a high rubber content present one major drawback: they require higher mixing and installation temperatures due to the elevated viscosity caused by the high rubber content and thus they produce larger amounts of greenhouse gas emissions than conventional bituminous mixtures. This article presents a study of the effect of four viscosity-reducing additives (Sasobit®, Asphaltan A®, Asphaltan B® and Licomont BS 100®) on a bitumen modified with 15% rubber. The results of this study indicate that these additives successfully reduce viscosity, increase the softening temperature and reduce penetration. However, they do not have a clear effect on the test for elastic recovery and ductility at 25 °C.

Using Sewage-Sludge Ash as Filler in Bituminous Mixes

In this study, the behavior of bituminous mixes made with sewage sludge ash (SSA) as mineral filler was investigated. The behavior of these mixes was evaluated with the Cantabro, indirect tensile strength, water sensitivity, permanent deformation, and resilient modulus tests. The results show that SSA waste may be used in bituminous mixes at approximately 2–3% weight percent, maintaining adequate levels of cohesion and adhesion in the mixtures, which is comparable to mixtures made with active fillers such as hydrated lime and cement. Moreover, its use does not increase permanent deformations. However, the resilient modulus test gave slightly lower results for mixes made with SSA than for mixtures made with other fillers. It may be concluded that SSA waste may be used as a filler for bituminous mixes with better results than for mixes made with limestone fillers and with similar results for mixes made with other fillers such as hydrated lime and cement.

(Table 1) Composition of bituminous substances in sediments from the East Pacific Rise

Bitumoid contents in metalliferous sediments from axial parts of the East Pacific Rise (EPR) have been studied. Maximal concentrations of bitumoid matter and aromatic hydrocarbons have been found in the axial zones of the EPR as a result of hydrothermal processes and accumulation of endogenous matter in the sediments. Distribution of bitumoids and hydrocarbons coincides with deposition of ore minerals that indicates similarity of their sources.

Development of a methodology for posting load limits on load-zoned pavements: interim report.

Texas Department of Transportation, Austin

Design and construction of continously reinforced concrete airport pavements : final report /

Final report; August 1977.

Short-term guidelines to improve crumb rubber modified asphalt concrete pavements. Final report.

Texas Department of Transportation, Austin

A summary of experimental concrete pavements in New York. Final report.

Federal Highway Administration, Office of Research, Development, and Technology, Washington, D.C.

Reflective characteristics of roadway pavements during wet weather.

"May 1986."

Effects of tire pressures on flexible pavements. Final report.

Mode of access: Internet.

Development of guidelines for posting load limits on pavements. Final report.

Federal Highway Administration, Washington, D.C.

Design manual: airfield pavements.

Cover title.

Plastic and swelling properties of bituminous coking coals /

Includes index.

Structural overlay strategies for jointed concrete pavements.

Cover title.

Incremental costs and performance benefits of various features of concrete pavements / [T.E. Hoerner, K.D. Smith, and J.E. Bruinsma]

"HRDI-11/04-04(1M500)E"--P. [4] of cover.