Glauco Tulio Pessa Fabbri

Fatigue Behavior of Asphalt-rubber Binders Modified With Shale-oil Residue

This work aims at evaluating the effects of the proportions of crumb rubber and shale-oil residue on the fatigue parameter G*sinδ. Eight asphalt binders were submitted to short- and long-term aging and then tests in the oscillatory-shear mode were performed. Based on regression models, response trace plots, and contour plots were made. Both rubber and oil reduce the G*sinδ parameter, increasing the controlled-mode fatigue resistance. As the test temperature decreases, the intensity of the effects of rubber and oil on G*sinδ increases and the number of mixtures that meet the Superpave limit of 5.0 MPa reduces.

A Comprehensive Study About Stresses in Upside-Down Pavements

This paper presents a study about the effect of thicknesses and resilient moduli of upside-down pavement layers on the stresses that occur on surface course. For this, a full factorial experiment was developed considering three layers upside-down pavement structures with thicknesses and resilient moduli variations, generating 20,160 experimental conditions, whose elastic behaviors were simulated using Elsym5 software. Factorial statistical analysis was used to evaluate the results and another simulation set was made evaluating variable effect separately. The results indicated that there is increase on tensile stresses on surface course when (i) there is decrease of the surface course thickness or increase of granular layer thickness; (ii) an increase of resilient modulus of surface course or a decrease of resilient modulus of granular base course. Cemented base course thicknesses, resilient modulus and the subgrade modulus have no or slight influence on surface coarse induced stresses.

Reuse of Waste Foundry Sand Mixed with Lateritic Clayey Soils in Pavement Bases and Sub-bases Courses

This paper evaluated the reuse of WFS mixed with lateritic clayey soils in pavements sub-bases and bases. Two lateritic clayey soils and one chemically bonded WFS were used in this study. A laboratory program was conducted on mixtures of lateritic clayey soils and WFS. Atterberg Limits, Particle Size Distribution, mini-CBR, CBR, hydraulic conductivity and Cyclic Triaxial Tests were used to assess mechanical properties of soil-sand mixtures. Environmental test was performed to determine leaching potential of the WFS. The results showed that soil-sand mixtures containing WFS have mechanical properties similar to the materials commonly used in bases and sub-bases courses.

Rheological Behavior of Asphalt–Rubber Binders Modified With Shale-Oil Residue and Polyphosphoric Acid

The objective of this paper is to assess the effects of adding two modifiers of different chemical nature on the rheological behavior of asphalt–rubber binders: the shale-oil residue and the polyphosphoric acid. Four modified asphalt–rubbers were prepared: asphalt–rubber–PPA (18 % crumb rubber + 1 % PPA), asphalt–rubber–oil (18 % rubber + 10 % shale-oil residue), asphalt–rubber–oil–PPA–1 (18 % rubber + 10 % oil + 1 % PPA) and asphalt–rubber–oil–PPA–2 (9 % rubber + 5 % oil + 0.5 % PPA). A reference asphalt–rubber was prepared using 18 % crumb rubber. The samples were submitted to oscillatory-shear tests to obtain data (complex modulus, G*, and phase angle, δ) to construct master curves. Compared to the base asphalt binder, the pure asphalt–rubber improves the rutting and strain-controlled fatigue resistances. The addition of 1 % PPA enhances even more the rutting resistance and improves slightly the fatigue resistance below 20°C. The most substantial increase in fatigue resistance is obtained when 10 % oil is added to the pure asphalt–rubber, but its rutting resistance is drastically reduced. Mixtures 1 (18 % rubber + 10 % oil + 1 % PPA) and 2 (18 % rubber + 5 % oil + 0.5 % PPA) have lower rutting resistance compared to the base asphalt–rubber, but only mixture 1 has higher fatigue resistance. Compared to the base asphalt binder, all modified asphalt–rubber binders present higher G*/sinδ values (at all rutting temperatures) and lower G*·sinδ values (only below 20°C) when traffic speed reduces. Taking this evidence into account, the asphalt–rubber and the asphalt–rubber–PPA are the most appropriate. Although shale-oil residue has shown opposite results at intermediate and high pavement temperatures (enhancing the fatigue resistance and reducing the rutting resistance), it is able to reduce the viscosity of the asphalt–rubber, enhancing the workability of the HMA mixes during construction.