Guaruman fiber: A promising reinforcement for cement-based mortars

Abstract

Guaruman fiber is a natural lignocellulosic fiber (NFL) extracted from the stalk of an Amazon plant (Ishinosiphon Koern), in the northern region of Brazil. The present work investigates the addition of 2.5, 5.0 and 7.5 wt% of guaruman fiber, into cement for a reference mortar. The fibers were mercerized in NaOH solution for improved adhesion to a mortar matrix made with 1:1:6 ratio of ordinary Portland cement, lime and natural sand. Technical properties of mass density, consistency, incorporated air content and water retention were for the first time evaluated for the as-processed fresh state of the mortar reinforced with this NFL. All methodologies used were adapted to the Brazilian technical standards. Relevant data were obtained from the international literature on the subject. It was found that the addition of NaOH-treated guaruman fiber practically does not affect the workability properties of the mortar. The results showed that the fiber surface treatment process promoted a mass density increase of ≈ 3% in the fresh state for the mortar with 7.5% of guaruman fibers. Meanwhile, this same trend was observed in water retention, which for the 7.5% mortar changed from 92.7%, with its fibers in the natural condition, to 94.24% in the treated condition. The incorporated air content increased in relation to the reference mixture, reducing comparatively in the treated conditions. These preliminary results in association with the relatively low mass density of the mortars incorporated with NaOH-treated guaruman fibers reveal a promising material to be applied as mortar for wall covering in civil construction, in a proportion of 7.5 wt%, which shows a great potential for the use of this fiber.