Degradation Kinetics and Durability Enhancement Strategies of Cellulosic Fiber-Reinforced Geopolymers and Cement Composites

Abstract

The need to overcome the low energy-absorbing response and low tensile strength of geopolymers and cementitious materials has motivated researchers to develop fiber-reinforced composites. Interestingly, natural cellulosic fibers provide exciting prospects for advancements in bio-based materials compared to synthetic fibers. Incorporating fibers in such binders offer a crack limiting effect by creating multiple cracks than forming one major crack, usually leading to improved toughness and tensile strength of the composites. However, their sensitivity in alkaline media and environmental fluctuations deteriorates their durability and reinforcing capacity in composites. Therefore, exploring suitable mitigation strategies for such drawbacks of natural fibers based on previous research work and figuring out the existing gaps for further developments is extremely important. In this paper, cellulosic fiber degradation in geopolymer and cement-based matrices and the respective remedial actions have been reviewed based on a comprehensive analysis of the available literature. The influence of fiber modification and matrix treatment on the durability and strength characteristics of such composites is thoroughly discussed. Finally, recommendations and suggestions for further research in the field are presented.

Alkaline Degradation of Plant Fiber Reinforcements in Geopolymer: A Review

“…Due to repeated expansion and contraction of PFs under the action of water, stress is generated inside the fibers, and microcracks are formed [ 40 ]. When free water enters PF cells, hydrogen bonds are formed between water and PF, so as to compound the fiber and matrix interface under the action of water [ 58 , 59 ]. In addition to alkaline degradation, the high hygroscopic properties of PFs also create favorable conditions for biodegradation.…”

“…Generally speaking, fiber degradation of PF-reinforced cement-based composites is accompanied by fiber mineralization. During the matrix hydration process, the Ca, Mg, Al, and silicon plasma impregnated fiber cell walls were defined as fiber mineralization [ 58 ]. As a result of the migration of hydration products such as calcium hydroxide into the PF cavity, the fiber wall, and interfiber void, the toughness of the composite decreases.…”

The Precursors Used for Developing Geopolymer Composites for Circular Economy—A Review

“…For example, the arrangement of cellulose microfibrils gives cellulose fibers a good resistance to chemical and biological attacks. On the other hand, the hydrophilic nature of hemicellulose under the action of acids and weak bases can be hydrolyzed and easily degraded at temperatures or following biological attacks [59]. Lignin being hydrophobic is very resistant to most attacks.…”

“…Practically, the strongly polarized hydroxyl (OH) groups are responsible for the hygroscopic nature of the fibers which leads to their separation in the interface area leading to poor adhesion to the geopolymer matrix. In this sense, solutions are being searched to avoid the degradation of the fibers by carrying out specific treatments, both in terms of geopolymer matrix and fibers [58,59]. One of the tartaring methods, to reduce the water absorption of cellulose fibers, is hornification.…”

Possibilities of Checking Water Content in Porous Geopolymer Materials Using Impedance Spectroscopy Methods

“…Geopolymer is a porous material with many excellent properties such as high compressive strength, good electrical insulation and resistance to chemical corrosion. Furthermore, the widespread pores in geopolymer matrix provide enough channels for ion storage and motion [ 8 , 14 , 15 , 16 , 17 , 18 ]. The interests of researchers in the world oscillate around alkali-activated materials, which include geopolymers.…”