Influence of Natural Fiber Properties on the Mechanical Performance of Unfired Earthen Blocks

Rapid population growth and accelerated urbanization are intensifying pressure on natural resources and the construction sector, which remains heavily dependent on conventional, high-carbon materials such as concrete and steel. In this context, compressed earth blocks are attracting renewed interest due to their environmental and socio-economic advantages. However, their low mechanical strength and limited durability require targeted performance improvements. This review explores natural fiber reinforcement as a sustainable strategy for enhancing the properties of unfired earth blocks. Drawing on over 60 peer-reviewed studies, it examines how fiber characteristics, dimensions, tensile strength, Young’s modulus, and biochemical composition, affect the compressive, tensile, and flexural strength of these materials. Findings show that reinforcement efficiency is determined not only by the intrinsic physical and mechanical properties of the fibers but also by fiber–matrix interfacial bonding and the experimental protocols employed. Importantly, fibers with high tensile strength do not necessarily yield improved performance when adhesion between matrix and fibers is poor. The review emphasizes the need for standardized testing procedures, detailed fiber characterization, and optimized surface treatments to improve compatibility with earthen matrices, thereby advancing the development of durable, low-carbon construction materials.