Application of natural and synthetic fibers in bio-based earthen composites: A state-of-the-art review

Abstract

• Use of fibers in improving the efficiency of bio-based composites is assessed. • Effect of fiber type, content and length on bio-treated soil efficacy is evaluated. • Analysis of factors impacting selection of fibers for bio-mediated soils is provided. • A thorough evaluation of cost-performance-balance is performed for used fibers. Bio-mediated ground improvement techniques including Microbial Induced Calcite Precipitation (MICP) and Enzyme Induced Calcite Precipitation (EICP) treatment methods are extensively being employed nowadays in a variety of construction projects as newly emerging sustainable and environmentally-friendly approaches to enhance the mechanical properties and durability characteristics of earthen composites. The intrinsic brittleness of MICP- and EICP-treated soils, however, considerably limits their applications in practical geotechnical engineering. The use of fiber reinforcement has been recognized to be an appreciably efficient solution to overcome such challenges and augment the ductility of biologically stabilized soils. Accordingly, there has been growing attention drawn to integrating natural and synthetic fibers into bio-based composites, opening up exciting possibilities for improved performance and versatility in different civil engineering applications. Despite the significance of the matter, no comprehensive review study has been conducted in this field thus far examining thoroughly the incorporation of both natural and synthetic fibers into bio-mediated materials from different perspectives and identifying key research gaps and avenues for future exploration in the development of advanced composites for diverse applications. To fill these gaps, this review article aims to examine the current state of research on utilizing fiber additives to enhance the effectiveness of MICP and EICP treatment methods in an attempt to provide an in-depth insight into the effects of fiber type, content, and length as well as the underlying mechanisms of fiber interactions within the porous structure of such treated soils. The applications of fiber-reinforced bio-cemented soils, their limitations, and the major challenges encountered in practice, as well as the potential areas of interest for future research and the key factors to be considered when selecting suitable fiber for optimal soil treatment using MICP/EICP, are all critically elaborated and discussed. By synthesizing the current research findings, the study provides engineers with a valuable resource to guide the development and optimization of fiber-reinforced MICP and EICP techniques for effective soil improvement and stabilization. Based on the findings of all relevant studies in the literature, a comprehensive cost-performance-balance analysis is conducted aiming to serve as a useful guideline for researchers and practitioners interested in applying fibers in various construction projects or other related applications where either MICP or EICP technique is being utilized as the main soil stabilization approach. The results show that the optimal contribution of natural and synthetic fibers in bio-treated soils to achieving maximum strength is typically recommended in the ranges of 0.5-3% and 0.2-0.6% in terms of fiber content, alongside 9-12 mm and 9 mm in terms of fiber length, respectively. Natural fibers like sisal and wool are considered as cost-effective options, while synthetic fibers such as carbon and basalt offer notable strength improvements at a higher cost. It is essential to carefully evaluate the balance between the desired enhancements in strength and the budgetary limitations of a project when choosing the most suitable fiber type to improve the performance and durability of composite materials.

Topics & Concepts