Performance evaluation of crumb rubber mortar reinforced with synthetic and banana fibers

• Main Author: Micheal Abel
• Format: Academic Exercise
• Language: English; English
• Published: 2022
• Subjects: TA401-492 Materials of engineering and construction. Mechanics of materials
• Online Access: https://eprints.ums.edu.my/id/eprint/35163/1/24%20PAGES.pdf; https://eprints.ums.edu.my/id/eprint/35163/2/FULLTEXT.pdf; https://eprints.ums.edu.my/id/eprint/35163/

The addition of crumb rubber as fine aggregate replacement in mortar have been known to decrease the mechanical properties of cement-based mortar. However, various methods have been investigated combat this problem such as the incorporation of various types of fiber like metallic, glass, polymer, carbon, mineral, and organic fibers in cement-based matrix. Generally, the objective of adding fibers in cement matrix is to improve the mechanical properties of its composite host through a crack-constraining scenario identified as the fiber-bridging phenomenon. The improvement in strength is dependent on various factors such as the matrix strength, fiber type, fiber modulus, fiber aspect ratio, fiber orientation, and aggregate size effects. In this study, synthetic polypropylene-polyethylene blend fibers are combined with natural banana fibers to improve the performance of crumb rubber mortar in compression, tension, and flexure. A total of 12 mix designs were developed with varying fiber combinations and rubber crumb replacement. Subsequently, a parametric study with chemical admixture was conducted at 3, 7, and 28 days to improve the flowability and the resultant mechanical properties of the HyFRM. It was observed that addition of fiber in the mortar matrix significantly decreases the workability as compared to the samples without fiber content. The reduction of compressive, tensile, and flexural strength was also observed to be directly proportional to the increase of crumb rubber content in the mortar matrix, and the HyFRM is observed to produce less compressive strength compared to mortar reinforced with single synthetic fiber. In tension, mortar samples C5F6 with 5% crumb rubber content and addition of 0.6% polypropylene-polyethylene blend fibers shows significant increase of 23.9% in split tensile strength compared to the control mortar. Significant decrease of flexural strength with an increase of crumb rubber content is also recorded for mortar samples at 3, 7, 28 days of curing.