Absorption and Strength Properties of Short Carbon Fiber Reinforced Mortar Composite

Md Safiuddin,George Abdel-Sayed,Nataliya Hearn

doi:10.3390/buildings11070300

Md Safiuddin, George Abdel-Sayed + Show 1 more

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https://doi.org/10.3390/buildings11070300

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Abstract

This paper presents the water absorption and strength properties of short carbon fiber reinforced mortar (CFRM) composite. Four CFRM composites with 1%, 2%, 3%, and 4% short pitch-based carbon fibers were produced in this study. Normal Portland cement mortar (NCPM) was also prepared for use as the control mortar. The freshly mixed mortar composites were tested for workability, wet density, and entrapped air content. In addition, the hardened mortar composites were examined for compressive strength, splitting tensile strength, flexural strength, and water absorption at the ages of 7 and 28 days. The effects of different carbon fiber contents on the tested properties were observed. Test results showed that the incorporation of carbon fibers decreased the workability and wet density, but increased the entrapped air content in mortar composite. Most interestingly, the compressive strength of CFRM composite increased up to 3% carbon fiber content and then it declined significantly for 4% fiber content, depending on the workability and compaction of the mortar. In contrast, the splitting tensile strength and flexural strength of the CFRM composite increased for all fiber contents due to the greater cracking resistance and improved bond strength of the carbon fibers in the mortar. The presence of short pitch-based carbon fibers significantly strengthened the mortar by bridging the microcracks, resisting the propagation of these minute cracks, and impeding the growth of macrocracks. Furthermore, the water absorption of CFRM composite decreased up to 3% carbon fiber content and then it increased substantially for 4% fiber content, depending on the entrapped air content of the mortar. The overall test results suggest that the mortar with 3% carbon fibers is the optimum CFRM composite based on the tested properties.

Highlights

Cement-based mortar is widely used because of its many beneficial properties, including good compressive strength, high fire resistance, ease of application, and low cost
This study presents the performance of carbon fiber reinforced mortar (CFRM) composites with respect to absorption and strength properties
The workability of mortar composite decreased with higher content of carbon fibers due to large surface area and interlocking of the fibers; the entrapped air content of CFRM composite was greater and its wet density became lower than that of NPCM

Summary

Introduction

Cement-based mortar is widely used because of its many beneficial properties, including good compressive strength, high fire resistance, ease of application, and low cost. Cement mortar possesses very low tensile and flexural strengths, limited ductility, and little resistance to cracking. It exhibits an elastic brittle behavior under tensile stresses. Internal microcracks are inherently present in cement-based composites, such as mortar and concrete When loaded, these microcracks propagate and gradually connect to each other. Due to poor tensile strength, the connectivity of microcracks increases and results in macrocracks that lead to the brittle fracture in cement-based composites. This inherent deficiency can be overcome by adding fibers, as they arrest the cracks and allow much larger deformation beyond the peak stress [2]. Many studies have reported that short fibers substantially improve the performance of cement-based composites under tensile and flexural loadings [3,4,5,6,7,8]

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