Reinforcement of Compressed Earth Bricks Using Locally-Sourced Triumfetta pentandra Fibers: Physical and Mechanical Evaluation

Abstract

This study explores the novel application of Triumfetta pentandra (TP, “Nkui”) fibers, a tropical plant that is abundant yet underutilized in civil engineering, to enhance the performance of compressed earth bricks (CEBs). The main objective is to assess how incorporating these vegetal fibers can improve the mechanical properties of CEBs while maintaining durability. TP fibers were extracted, characterized, and integrated into the soil used for brick specimens. A rigorous experimental protocol was implemented, featuring a unique fiber pre-treatment, the use of a single, homogeneous clayey soil type, and controlled 28-day curing under standard humidity and temperature, which distinguishes this study from previous works. Physical measurements (moisture content, bulk density, water absorption) and mechanical tests (fiber tensile strength, compressive and flexural strength of CEBs) were conducted following French standards. The results indicate that 4 % TP fiber content yields optimal mechanical performance, with compressive strength reaching 6.61 MPa and flexural strength 1.49 MPa at 28 days, compared to 5.16 MPa and 0.51 MPa for unreinforced samples. This demonstrates the potential of TP fibers to reinforce earth-based materials, providing a sustainable, locally sourced, and cost-effective construction solution. However, higher fiber content increases porosity and capillary water absorption (up to 16.75 g at 6 % fibers), highlighting the importance of optimized fiber dosing and potential complementary treatments for long-term durability.