Abstract
This study compares the structural and morphological changes in Guadua angustifolia Kunth (GAK) fiber prepared in three different ways (chips, barkless and crushed) when non-conventional alkaline treatment is applied. Moreover, it shows the improvement of mechanical properties of cement composites reinforced with these treated fibers. The three different preparations of Guadua were treated with a saturated solution of calcium hydroxide (5%) at 125 °C and 1.25 kPa for 3 h to remove non-cellulosic compounds. Then, their chemical, morphological, and structural properties were examined. The fibers exhibiting the higher delignification rate were selected to prepare cement composite boards, whose mechanical properties were successively compared with those of composites reinforced with untreated G. angustifolia fibers. The water/cement ratios of the cement mixed with the Ca(OH)2-treated and the untreated fibers were, respectively, around 0.3 and 0.25. The flexural strength and toughness of the two composites were evaluated after 7, 28, and 90 days of curing. The calcium hydroxide treatment showed higher efficiency in removing non-cellulosic materials when performed on crushed bamboo; moreover, the mechanical properties of the composites reinforced with the treated fibers were higher than those mixed with the untreated ones. After 90 days of curing, the flexural strength increased by around 40% and the toughness became three times higher (p < 0.05). The mechanical improvement by the Ca(OH)2 treatment of G. angustifolia fibers demonstrates its potential for the fabrication of cement composites.
Highlights
In recent years, there has been a fast rise in the use of renewable natural fibers as reinforcing agents of cement materials [1,2] in order to reduce their environmental impact
Guadua angustifolia Kunth (GAK) samples were taken from the internodes of the middle culm, which is the part most used for construction in Colombia and is widely commercialized, of plants grown for four years in an experimental field in La Tebaida, Quindío
For the compositecement cementboards boards (CCBs) reinforced with Ca(OH)2-treated fibers, this increase reached 57% varying from 5.2 MPa after 7 days to 8.2 MPa after 90 days
Summary
There has been a fast rise in the use of renewable natural fibers as reinforcing agents of cement materials [1,2] in order to reduce their environmental impact. Several chemical modifications have been tested to increase the fiber roughness and the amount of cellulose exposed on their surface [12,13,14] In this viewpoint, alkali treatments are one of the major techniques adopted to obtain fibers with adequate properties for reinforcement applications due to their low cost. Alkali treatments are one of the major techniques adopted to obtain fibers with adequate properties for reinforcement applications due to their low cost They can change the morphology of natural fibers by removing the impurities from their surface; for example, they can disrupt the lignin structure and break the linkage between lignin with the other carbohydrate components of lignocellulosic biomass [15]. The effect on the flexural strength and toughness of CCBs was studied
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