Effect of Coir Fiber Reinforcement on Flexural and Compressive Strengths of Masonry Mortar

An appreciable quantity of cement is consumed as binder for masonry mortar, which has resulted in cost escalation and high energy consumption in building construction, in addition to contributing to greenhouse gas emissions. On the other hand, disposal of waste lignocellulosic materials as agricultural residues persists as an unsolved technical problem creating environmental pollution. This paper proposes an effective solution for these two critical issues. Coir fiber, when used as a reinforcement material in cement, was found to be effective in enhancing the mechanical properties of the binder. The application of coir fiber reinforcement on strong, moderate, and weak masonry mortars with respect to strength criteria is examined in this study. ANOVA analysis was carried out to examine the level of significance of coir fiber reinforcement on the flexural and compressive strengths of masonry mortar. The findings from the study revealed that 0.5% coir fiber reinforcement enhanced flexural strength of strong mortar by 18%–22%, moderate mortar by 21%, weak mortar by 10%, and compressive strength of strong mortars by 16%–19% by contributing strength in the early curing period. Moreover, coir fiber–reinforced mortars satisfied the compressive strength criteria required of strong mortar (7.5 to $10\mathrm{N}/{\mathrm{mm}}^2$), moderate mortar ($5\mathrm{N}/{\mathrm{mm}}^2$), and weak ($3\mathrm{N}/{\mathrm{mm}}^2$) mortar for its application as mortar on masonry walls in accordance with Indian standards.

The strength of masonry in compression, flexure, and shear determines how well masonry operates structurally. Cement-based structures are strong in compression but are prone to shrinkage cracks over a span of 30 years due to its weakness in tension. Flexural strength is an indirect indicator for measuring tension. Coir fiber imparts tensile strength to the matrix when used as reinforcement in cement mortar. Fiber networking dissipates the tensile stresses that develop in mortar during flexure and would bridge the gap in a better way. This prolongs the life of buildings and maintains ecological equilibrium by preventing the need for periodic repair and maintenance, which reduces cost, time, and labor. The use of fibers in mortar for plastering is found to be more beneficial in enhancing the strength of a masonry structure than adding fibers to blocks. Coir fiber content of 0.25% and 0.5% (10 mm length) by weight of cement was found to be effective at enhancing the early flexural strength of cement mortar. Coir fiber–reinforced plaster cement can be made available ready to use in bags of 25 or 50 kg for a crack-free plastered surface on ceilings and internal and external walls.