Avaliação da estabilidade de fibras de polipropileno em meios agressivos aos materiais a base de cimento

AUTOR(ES)
DATA DE PUBLICAÇÃO

1995

RESUMO

The use of polypropylene fibers in cement based materials has increased in the last years as a substitute for mineral and metallic fibers and as an alternative method to improve the mechanical properties of concrete. This work evaluated the stability of polypropylene fibers in aggressive environments to cement based materials by monitoring average molecular weight changes through viscosimetry and degradation products formation through infrared microspectroscopy. The aggressive baths used were cement with water, sulfuric acid 10M, 1M and 0,1M, NaOH 0,1M, synthetic sea water and water(control). Ultraviolet irradiated fibers were used to obtain maximum degradation, for this work conditions. A maximum value of 0,9 was obtained for carbonyl index, 3 for hidroxyl index and 1 for the rate between region area for 1672cm to 1540 cm and reference area. Irradiated fibers viscosimetric analysis showed a decrease in average molecular weight. For zero irradiation time v = 134±3kg.mol, for 24h irradiation time v = 37±1 kg.mol and for 72h v = 0,23±0,20 kg.mol. The infrared microspectroscopy analysis of the fibers left in aggressive baths showed changes in the 1746cm band (carbonyl groups) quantified by carbonyl index (C.I.). Changes in the 1718 to 1524 cm region (other degradation products) were observed and quantified (O.I.). These changes point to a different degradation path with respect to U.V. irradiation. Carbonyl products formation were observed in fibers left for 230 days in cement with water (C.I.0,20), sulfuric acid 10M (C.I.0,15), 1M (C.I.0,14), 0,1M (C.I. 0,16), NaOH 0,1M (C.I.0,15) and synthetic sea water (C.I.0,15), at 4°C (control: C.I.0,10). At ambient temperature, carbonyl products were observed in fibers left in cement with water (C.I.0,17), sulfuric acid 1M (C.I.0,17), 10M (C.I.0,15) and NaOH 0,1M (C.I.0,15). Other degradation products were formed in fibers left in cement with water (O.I.0,40), sulfuric acid 0,1M (O.I.0,38),1M (O.I.0,23) and NaOH 0,1M (O.I.0,28), at 50°C, with respect to the control (O.I.0,04). In general, cement with water is the most aggressive environment for polypropylene fibers, among the baths studied. Accelerated aging studies of the fibers in concrete are necessary to conclude about their use in cement based materials.

ASSUNTO(S)

fibras polipropileno

ACESSO AO ARTIGO

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