Effect of Adding Phragmites-Australis Fiber on the Mechanical Properties and Volume Stability of Mortar

Abstract

In this research, the investigation focuses on the influence of Phragmites-Australis (PA) fibers on the mechanical properties and volume stability of mortar. A total of four mixtures were employed with varying amounts of locally sourced PA fibers ranging from 0.5% to 2% (by volume). Testing includes flexural strength, compressive strength, chemical shrinkage, drying shrinkage, autogenous shrinkage, and expansion. The findings show that the use of PA fibers caused a reduction in compressive and flexural strength. However, beyond 3 days of curing, an increase in flexural strength ranging from 7 to 21% was observed at 1% PA fiber compared to the control sample. Furthermore, the addition of PA fibers up to 2% effectively mitigates the dimensional stability of mortar samples. A gradual decrease in chemical, autogenous, and drying shrinkage as well as expansion occurs in mortar samples when % of PA fibers increases. At 180 days, this reduction was 37, 19, 15 and 20% in chemical shrinkage, autogenous shrinkage, drying shrinkage, and expansion, respectively, for a mix containing 2% PA fiber. Additionally, a hyperbolic model is proposed to predict the variation of length change with time. Also, a strong relationship is observed between chemical shrinkage and other length change parameters. Consequently, the environmentally friendly utilization of PA fibers demonstrates its potential to significantly enhance mortar durability in construction applications.

Volume Stability and Mechanical Properties of Cement Paste Containing Natural Fibers from Phragmites-Australis Plant at Elevated Temperature

“…The decrease ranged from 10 to 23% compared to the reference mix. These results indicate that, in the long term, PhA fibers form a robust bond and contribute to the cohesion of materials within the matrix [35]. This phenomenon is consistent with the findings of the ILRC, where similar percentage decreases were observed with the addition of PhA fibers.…”

“…The IRLC denotes the pace of shrinkage or expansion during the initial phases of volume change due to moisture loss or absorption, while the ULC indicates the maximum expected value of shrinkage or expansion after reaching a stable moisture content level. To analyze those crucial parameters and to determine the length change (CH-S, DR-S, AU-S, and EXP) with time, a hyperbolic model (Figure 5) was used as follows [35,36]:…”

“…This decrease was equivalent to 8.1 and 15.3% compared to the control mix. This decrease may have been due to the presence of PhA fibers, which may have absorbed some of the heat of hydration, thereby decelerating the hydration process of the paste [35].…”