Bond Strength of Coir Fibers in Cement-Stabilized Rammed Earth Matrix

Cement-stabilized rammed earth (CSRE) is a monolithic construction used in the construction of load-bearing walls. CSRE predominantly undergoes catastrophic shear failures under compression. Short randomly oriented fiber reinforcements have the potential to enhance the CSRE ductility and its postpeak response. The literature available on fiber-reinforced rammed earth was mainly focused on overall mechanical properties of the material, but very little is known about the fiber–matrix interfacial properties. The fiber–matrix interfacial bond characteristics play a significant role in the mechanical behavior of fiber-reinforced composite. Understanding the postpeak behavior of fiber-reinforced composites such as coir fiber–reinforced CSRE necessitates the information on interfacial bond strength of the fiber and the matrix. In the present study, the bond strength between the coir fiber and the CSRE matrix was explored using pullout tests. The study shows that pullout resistance of the fiber in the CSRE matrix depends on the fiber embedment length, dry density, cement content, and moisture content. The current investigations focused on these parameters. The critical fiber embedment length for the natural coir fiber in the CSRE matrix was found to 25 mm. The use of chopped fibers less than the critical embedment length can help in the design of ductile earthen construction materials with improved postpeak response.