Sisal fiber degradation treatment by different methods for cement composite materials

Sisal fiber is the most extensively cultivated and strong natural fiber extracted from the Agave-sisalana plant leaf. The use of sisal fiber in concrete or mortar has a lot of benefits, however it degrade due to mineralization from cementitious materials and moisture absorption. Numerous studies have explored surface treatment methods to reduce this deterioration, however the combined effects of different treatment approaches on the performance of sisal fiber in cement composites remain not well known. This study addresses this gap by systematically evaluating the influence of calcined bentonite, varying concentrations of alkaline solutions by 5% and 10% NaOH, additionally, using 150 °C and 200 °C thermal treatments on reducing the degradation of sisal fiber in cement-based materials. The findings reveal that all three treatments-thermal, alkaline, and calcined bentonite-were effective in removing lignin and surface impurities from the fibers. Notably, fibers treated with 5% sodium hydroxide, heated to 150 °C, or treated with calcined bentonite exhibited improved durability after 10 wetting and drying cycles, showing increases in breaking load resistance of 28.95%, 32.11%, and 33.37%, respectively. These treatments also significantly reduced water absorption by 34.89%, 29.27%, and 60.95%, compared to untreated fibers. Moreover, the calcined bentonite-treated fiber showed reduced mass loss by 28.18% at 367 °C and 29.08% at 600 °C when compared to raw sisal fiber. Incorporating the treated fibers into mortar mixtures resulted in reduced fresh density and enhancements in both compressive and flexural strength. Specifically, fibers treated at 150 °C and with calcined bentonite improved the 28 days compressive strength by 23.31% and 23.44%, respectively, compared to mortar with untreated fibers.