Efeito de fibras sintéticas nas propriedades de ligantes e concretos asfálticos

AUTOR(ES)
DATA DE PUBLICAÇÃO

2010

RESUMO

The asphalt cement plays a major role in hot mix asphalts (HMA) by bonding the mineral aggregates and conferring impermeability. Despite the relatively small percentage of asphalt cement in hot mixes, the mechanical properties of asphalt layers are highly dependent on the quality of the binder. The physical and rheological properties of asphalt binders can be improved by the addition of modifiers, such as polymers and synthetic fibers. The main objective of this dissertation is to investigate the influence of a blend of polypropylene and aramid fibers added to a conventional binder classified as CAP 50/70 (Brazilian penetration grade). The polypropylene (PP) fibers supposedly act as real modifiers, being incorporated into the straight binder, while the aramid fibers should remain intact and act as a mechanical reinforcement to the HMA matrix. In order to evaluate the first effect, several samples of modified binders were prepared by incorporating different percentages (0% to 3%, every 0.5%) of PP fibers. The modified binders were subjected to conventional tests, such as penetration, rotational viscosity and softening point, before and after an aging process in rolling thin film oven (RTFOT). The stability to storage was also verified. Most of the physical properties showed some small improvement with the addition of PP fibers. In order to check the mechanical effects of blend mix of fibers, the author prepared porous asphalt mixes, known as CPA, using aggregates (gap graded gradation, envelope IV) specified by Brazilian standard DNER ES 386/99. The amount of the blend of fibers corresponded to 0.05% of the weight of the total mix. After investigation the best dosage, the samples of CPA were subjected to the following mechanical tests: indirect tensile strength, modulus of resilience, Cantabro abrasion, fatigue life (using indirect tension) and static creep. Based on the results of this experimental campaign, the benefits of the addition of these fibers were contradictory. Compared to samples using conventional binders, the samples with fibers generally produced higher indirect tensile strength, higher fatigue life and high resilient modulus, but also resulted in higher Cantabro loss and higher permanent deformations during the creep test. The parameters calibrated from these tests for conventional and modified/reinforced samples were used to perform mechanistic analyses of a typical pavement structure, using program Kenlayer. For the conditions analyzed here, the pavement using fibers did not perform better than the conventional one. Possible gains in fatigue life were counterbalanced by the higher resilient modulus of the modified mixes. Permanent deformations were also higher, due to creep effects.

ASSUNTO(S)

asfaltos e misturas modificadas fibras de ceramida e polipropileno avaliação da ligante modificada modified asphalts and mixtures evaluation of the modified ligand mechanical evaluation of the binder modified avaliação mecânica da ligante modificada geotecnica ceramide fibers and polypropylene

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