Effect of polypropylene fiber length on the flexural and compressive strength of compressed stabilized earth blocks

Earthen masonry is generally brittle, weak and poor in damage resilience. There is historic evidence that natural fibers such as straw and horsehair have been used to reinforce earthen masonry to prevent desiccation cracks and improve tensile strength. However, fibers have also been known to negatively affect mechanical properties such as compressive strength (an important quality control parameter for load bearing masonry) by creating voids and lowering density. This paper reports on findings of a study directed at investigating the feasibility of avoiding such problems in compressed and stabilized earth blocks through optimizing the fiber length when using soil from Newberry, Florida. Standard polypropylene fibers were selected for the study. The two different lengths of fibers studied were 54 mm and 27 mm. The test results showed a general improvement in compressive strength of the fiber reinforced matrices compared to the unreinforced ones. While an improvement in modulus of rupture (MOR) was observed for matrices reinforced with 54 mm fibers, results varied for the other fiber-reinforced matrices. An improvement in post-initial crack behavior was observed for all fiber-reinforced matrices compared to the unreinforced ones. The 54 mm fibers yielded the best results based on the influence on MOR, compressive strength, and deformability compared to the other matrices. INTRODUCTION Earth has been used as a construction material since early civilization. Adobe, molded earth, wattle and daub, and cob are all forms of earthen construction that have been in existence for centuries. Globally, about a third of the human population resides in earthen shelters. In developing countries, the number is estimated to be as high as 50% (Minke, 2009).The use of locally available materials is highly encouraged by proponents of the green building movement. It is generally accepted that earthen masonry is a green material considering that at it uses indigenous soils 661 Construction Research Congress 2014 ©ASCE 2014