Study of the technical feasibility of the use of ash of the Pinus burning in hot-mix asphalt

Author(s)

Vivian Silveira dos Santos Bardini

• Document type: Master's Dissertation
• Press: São Carlos.
• Institution: Universidade de São Paulo (USP). Escola de Engenharia de São Carlos (EESC/SBD)
• Defense date: 2008-05-21

Examining board members

Jose Leomar Fernandes Junior; Glauco Tulio Pessa Fabbri; Sandra Oda

• Advisor: Jose Leomar Fernandes Junior

Abstract

The industrial production of MDF - Medium Density Fiberboard - uses Pinus wood skin as a fuel, which, after the burning process, generates a fine gradation residue, an ash that is an environmental problem due to the content of some substances, above the quantity allowed by the NRB 10004:2004, and it is classified as a class II-A - non-inert product. The general purpose of this work is to test the hypothesis that the residue can be use as a filler in hot-mix asphalt, through the evaluation of technological properties by laboratory tests such as indirect tension, resilient modulus, fatigue life, moisture susceptibility, Marshall stability and creep. The evaluation of specific gravity of the residue was done by the gas pycnometer method. Initially, the substitution of the mineral filler by the residue was done in terms of weight, but the preliminary results showed that the best option was the substitution in terms of volume. The Marshall mix design for mixtures containing the residue resulted in a binder content approximately constant for both residue contents considered in this work (3.5% and 6.0%). The indirect tension test results showed higher values for mixtures containing 3.5% of mineral filler, being the lowest values associated to mixtures that use residue. The higher the filler content, the higher the resilient modulus and mixtures with mineral filler presented higher resilient modulus values. Only the mixture with 6.0% of mineral filler passed the moisture susceptibility test, and mixtures with residue presented higher moisture susceptibility. The residue also weakened the fatigue life, being the difference higher for mixtures with lower filler content. Although the results show a worsening of asphalt mixtures properties due to the use of the residue as a filler, for most of the obtained results the value remained above the minimum acceptable by technical standards, encouraging further researches on this subject, mainly due to the environmental problem associated to the burning of Pinus wood skin. (AU)