Porosity of asphalt concrete made with waste shredded-tire rubber-modified binders

Most bituminous paving researchers agree that high air void content (high permeability) should be avoided in the design and construction of bituminous pavements. Void content in bituminous mixtures is one of the main approaches in determining the optimum binder content. The current design procedures and the Leeds design method provide an approach to determination of the air voids in bituminous mixtures. Because the determination of porosity in bituminous mixtures is based on a calculated value, which is dependent on the accuracy of the mix composition, it is difficult to use porosity as a crucial parameter for acceptance of constructed bituminous pavements. In fact, porosity measurements are often the source of dispute and disagreement between contractor and engineer. For this reason, it is important to develop methods for the direct measurement of porosity in the laboratory so that verification in the field can be made independent of the compaction of the mix. This paper introduces a new porosity measuring procedure based on the Leeds vacuum porosity meter and presents the results obtained from this apparatus for asphalt concrete made with shredded-rubber modified binder.