Showing papers by "Hugo Manuel Ribeiro Dias da Silva published in 2009"

Assessment of the performance of warm mix asphalts in road pavements

Abstract: Several processes and products are available to produce warm mix asphalt (WMA). These may reduce the mixing and compaction temperatures in relation to hot mix asphalt (HMA), ensuring the necessary performance in the pavement. Lower plant mixing temperatures mean reduction in fuel consumption and lower emissions, possibly contributing to diminish health and odour problems and to decrease costs. During this work, two commercial additives (Sasobit® and Cecabase®) were used to produce WMAs, which were compared with a conventional HMA. Initially, the mixtures were designed, the amount of additive was selected (based on the binder characterization) and the mixing temperatures of the WMAs were chosen by means of EN 12697-10 compactability comparison. Then, a road trial was built and test specimens were collected (both of HMA and WMA) for volumetric composition and mechanical behaviour assessment. This study essentially provides a better understanding of the good performance capabilities of WMA mixtures.

Evaluation of the rheological behaviour of Warm Mix Asphalt (WMA) modified binders

Abstract: Several processes and products are available to produce warm mix asphalt (WMA). The use of those may reduce the mixing and compaction temperatures in relation to hot mix asphalt (HMA), ensuring a good performance of the pavement. Lower plant mixing temperatures mean reduction in fuel consumption and lower emissions, what may contribute to diminish odours and health problems. A laboratory study on the properties of the modified binders (using two commercial WMA additives—Sasobit® and Cecabase®) was carried out through conventional (penetration, softening point), dynamic viscosity and rheology (DSR) tests, in order to establish the optimum additive content. Stripping of binder from the aggregates is a reported problem in WMA. Thus, the affinity of the modified binders was assessed without encountering significant problems. It was also observed that only Sasobit® alters the viscosity of the binder. A maximum temperature reduction of 15°C was achieved using 4% of Sasobit® with a softer binder.

Rheological and functional evaluation of the interactions between bitumen and rubber

Abstract: It is estimated that about ten kilograms of tires are discarded per inhabitant annually. The negative impact of this residue can be reduced, since rubber can be reused as a constituent of asphalt rubber (AR) binder in road pavements. However, the materials which constitute the AR binders and their interaction are not sufficiently characterized. In this work several base bitumens interacted with crumb rubber, in order to produce AR binders, which were subsequently separated, by using a modified “Basket drainage method” to recover the residual bitumen and rubber. EN 12591 or 14023 standards tests and the Dynamic Shear Rheometer (DSR) were used to evaluate the changes in the properties of the binders during AR production. The swelling and depolymerisation changes in the rubber were evaluated through microscopic tests. It was observed that the characteristics of the base bitumen significantly affect the rubber and the AR binder properties (mainly for interactions with softer bitumens).

Avaliação do desempenho de misturas betuminosas temperadas

Abstract: Dissertacao de mestrado em Engenharia Civil (area de especializacao em Engenharia Rodoviaria)

Fabrico de misturas betuminosas de alto módulo a menores temperaturas com betume 35/50 e parafinas

Abstract: A industria da pavimentacao contribui de forma significativa para a emissao de gases causadores do efeito estufa e do desequilibrio da atmosfera terrestre. Recentemente temse desenvolvido um conjunto de novas tecnologias para reduzir a temperatura de producao e aplicacao das misturas em obra, que ainda sao mais relevantes para as misturas de alto modulo (MBAM) que sao produzidas a temperaturas mais elevadas. Este estudo tem por objectivo avaliar se e possivel reduzir a temperatura de fabrico e compactacao das MBAM sem comprometer o seu desempenho mecânico. Para tal, produziu se uma mistura convencional AC 20 base 10/20 (MBAM) que se comparou com uma mistura equivalente modificada com parafinas AC 20 base 35/50+Sasobit (MBAM) produzida a menores temperaturas. Este aditivo aumenta a viscosidade do betume nas temperaturas de servico e reduz a mesma durante o fabrico (favorecendo o envolvimento dos agregados a menores temperaturas). Neste trabalho procedeu-se a formulacao das misturas MBAM, a caracterizacao dos ligantes, a seleccao da temperatura de producao da MBAM modificada e a comparacao entre o desempenho das MBAM modificada e convencional, realizando ensaios de sensibilidade a agua, modulo de rigidez, fadiga e deformacao permanente. Foi possivel concluir que a MBAM modificada tem uma sensibilidade a agua e uma resistencia a fadiga e a deformacao permanente equivalente a MBAM convencional. Apenas se verificou uma ligeira quebra (12%) no valor do modulo de rigidez da MBAM modificada, para uma elevada reducao da temperatura de fabrico e compactacao (35oC), o que permite diminuir bastante os custos energeticos, ambientais e com o betume.