Silvino Capitão

Assessment of the Use of Hot-Mix Recycled Asphalt Concrete in Plant

Hot-mix recycled asphalt concrete in plant is one of the available techniques to perform cost and environmental effective pavement recycling. It is not commonly used in Portuguese paving practice basically because there is a lack of confidence at the end of the production chain. A study was conducted using mixtures from four trial sections, one with a traditional mixture for reference and three with 20, 30, and 40% of reclaimed asphalt concrete from a flexible pavement. The mix production was made in a batch plant without heating the reclaimed material. The laboratory process produced the same kinds of mixtures for comparison. Laboratory tests aimed to establish some fundamental properties for both the trial sections and laboratory mixtures: stiffness modulus, resistance to fatigue, and permanent deformation behavior. This paper contains the comparative results and indicates some useful directives for the use of such materials. It can be stated that for all the analyzed recycled mixtures the level of confidence should be similar to the one offered by the asphalt concrete produced from virgin materials.

Applications, properties and design of high modulus bituminous mixtures

ABSTRACT High modulus bituminous mixtures (HMBM) have been used for almost two decades in several countries. This paper presents an overview of use of this kind of bituminous material, as well as a summary of its typical compositions and mechanical properties. The rehabilitation of a structural layer on the EN14 (Portuguese national highway 14) using HMBM has been adopted as a case study. The project workplan involved the laboratory design of the mixture by undertaking performance tests to observe the effectiveness of the mixture. Prismatic specimens were extracted from constructed trial sections and similar specimens have been produced in the laboratory. Repetitive four-point bending tests were performed on both specimens for several temperatures and loading conditions. This made it possible to determine their stiffness modulus, phase angle and fatigue resistance. In addition, cores and slabs taken from trial sections have been used to characterise the permanent deformation behaviour of HMBM in laboratory. Wheel-tracking and repetitive loading axial tests (RLAT) were adopted for that purpose. The findings have led to some recommendations for the design of HMBM.

Assessment of warm-mix asphalt concrete containing sub-products as part of aggregate blend

ABSTRACT The study compares warm-mix asphalt concrete (WMA) and a traditional hot mix asphalt concrete (HMA), evaluating permanent deformation, fatigue, stiffness modulus, and water sensitivity. The cost (construction only) differences are also addressed. Three WMA blends were prepared. One WMA was manufactured with the stand alone organic wax and incorporated 60% of recycled concrete aggregate (RCA). The other two used organic wax embedded in cellulosic fibres, one of them incorporated 35% of reclaimed asphalt pavement (RAP), and the other had no added sub-product. Trial sections were constructed with plant-produced mixtures, laid and compacted with conventional equipment. When considered a global indicator representing mixtures mechanical behaviour involving deformation, rutting, fatigue and moisture resistance, the results showed that performance of WMA blended with RAP and RCA was similar to HMA, and the conventional WMA was 25% better. The construction process proved to be feasible for any WMA. The direct construction costs as compared to conventional HMA were 6% higher for the conventional WMA and 5–8% lower when WMA used sub-products. The use of these sub-products is aimed to find innovative approaches to be undertaken throughout the product lifecycle, from manufacture through reuse, with the goal of reducing waste going to landfill.

Tecnico accelerated ageing (TEAGE) – a new laboratory approach for bituminous mixture ageing simulation

ABSTRACT The available methods for accelerated ageing simulation in laboratory of compacted bituminous mixtures are often not representative of the ageing mechanisms experienced in the field. The objective of this study was to develop an alternative ageing method, Tecnico accelerated ageing (TEAGE). The method is intended to simulate the ageing of bituminous mixtures under specific environmental conditions by applying watering/drying cycles and ultra-violet (UV) radiation in equivalent levels to those observed in the field during a certain time. In this study a type of mixture was aged using TEAGE and LTOA (long-term oven ageing) methods and then tested for mechanical performance conducting stiffness, fatigue resistance and indirect tensile strength tests. Additionally, the chemical composition of the water used for the watering/drying cycles was analysed and recovered binders were tested for softening point and penetration. TEAGE-aged specimens showed clear evidence of an ageing gradient through the specimens’ depth, substantial reduction in fatigue life (15% reduction in Ԑ6) and a visible effect on the colouration of the UV exposed surface when compared with LTOA-aged specimens. The overall results and comparison with other studies indicate that TEAGE framework addressed in a more consistent way the ageing mechanisms that could be seen in the field.