The recent use of aramid fibers in geotextiles for ground reinforcement raises fundamental durability issues, in particular in alkaline soils where they are subjected to hydrolysis. To study the degradation mechanisms in such an environment, accelerated aging at pH 9 and at pH 11 has been carried out for up to one and a half years. This work describes the morphological evolutions that occur and the morphology-properties relationship during aging in moderately alkaline environments. The decreases in apparent density are larger at pH 9 than at pH 11, whereas the bulk chemical degradation is more extensive at pH 11 than at pH 9. Scanning electron microscopy micrographs of chemically etched fibers and the measurements of the local elastic modulus by nanoindentation support these results. Finally, this study has indicated an inverse correlation between the porosity level and the tensile strength. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012