Durability of plant fiber reinforced alkali activated composites

Abstract

Despite the numerous studies on plant fiber-reinforced alkali activated composites (PFRAAC), the durability of PFRAAC, a property that is of great significance to the reliability of the composites, has been little studied. The present study investigated the durabilities of PFRAAC in indoor, out door, and bagged environments and analyzed the appearance and microstructure of the specimens. A 360 d durability test revealed that the indoor specimen retained the highest percentage of bending strength, followed by the bagged specimen, and then the outdoor specimen. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy analyses showed that such a strength change trend was mainly attributed to the following: Owing to the effect of wet–dry cycles, the free alkali inside the matrix of the indoor specimen migrated to the specimen surface and, as a result, the alkalinity of the specimen internal region was lowered, thereby reducing the erosion of fibers by free alkali and resulting in only a small decrease in strength. The outdoor specimen was affected by the harsh climate, and hence, the matrix and fibers were severely eroded; consequently, the fiber–matrix bond significantly deteriorated, and the strength decrement was greater than those of the other specimens. The fibers of the bagged specimen were severely eroded by free alkali, and thus, their ductility was reduced, leading to a strength decrement between those of the indoor and outdoor specimens.