Abstract
This paper presents the results of an experimental investigation conducted to evaluate the mechanical properties, including strength and flexural toughness of hybrid fiber-reinforced mortar (FRM) containing various combinations of steel and carbon fibers with different material characteristics. The mortar specimens were mixed with steel and carbon fibers in the mix proportions of 100 + 0%, 75 + 25%, 50 + 50%, 25 + 75%, and 0 + 100% by volume at a total volume fraction of 1.0%. The flexural performance (flexural strength and toughness) of the mortar specimens was obtained using the third-point loading arrangement stipulated in the test methods of ASTM C 1609/C 1609/M and KS F 2566. In addition, compressive strength was also measured according to the KS F ISO 679 test method. Their mechanical properties were examined and compared with plain mortar (PM) at the age of 28 days. The test results showed the highest compressive and flexural strengths in the hybrid FRM reinforced with 75% steel fibers + 25% carbon fibers, confirming the synergistic reinforcing effect of the steel and carbon hybrid fibers. However, the hybrid FRM reinforced with 50% steel fibers + 50% carbon fibers has obtained slightly low flexural strength but owned the highest flexural toughness and hence can be judged as the most appropriate combination to be employed in hybrid FRM to improve the flexural toughness. Moreover, the fractured FRM surface was also observed via scanning electron microscopy (SEM) after platinum coating in vacuum. These results would be of great help in establishing the microstructural mechanism of hybrid reinforcing fibers in the cement matrix.
Highlights
Cement-based composites, due to their excellent compressive strength, have been widely used worldwide as major construction materials for civil engineering structures and buildings [1,2,3]
The average compressive strength of the hybrid fiber-reinforced mortar (FRM) reinforced with 75% steel fibers + 25% carbon fibers was 46.9 MPa, which was the largest in this experiment. e reason for this increase in the compressive strength was that carbon fibers were used to reinforce the microcarbon fibers, which were relatively small in size compared with steel fibers
All the FRM except for hybrid FRM reinforced with 75% steel fibers + 25% carbon fibers showed a somewhat lower compressive strength than plain mortar, and the strength tended to decrease considerably as the carbon fiber increased. e average compressive strength of a single FRM reinforced with carbon fiber alone was 35.6 MPa, and as a result, the average compressive strength was significantly reduced by about 22.4% compared with plain mortar
Summary
Cement-based composites, due to their excellent compressive strength, have been widely used worldwide as major construction materials for civil engineering structures and buildings [1,2,3]. Cement-based composite materials have two well-known weaknesses: they are vulnerable to the flexural·tensile strength and have low deformation performance [4,5,6,7]. To compensate for these shortcomings, fiber-reinforced cement composites (FRCC), in which discontinuous and chopped fiber materials are irregularly dispersed in cement composites, have been developed and are increasingly applied [8,9,10,11,12,13,14]. Fibers employed in FRCC are classified into microfibers and macrofibers according to their size (length and diameter). Macrofibers are 25∼80 mm long and 0.2∼0.8 mm in Advances in Civil Engineering diameter, and they are divided into steel fiber [6, 26,27,28,29,30] and synthetic fiber [31,32,33,34,35,36] by size. e microfiber is stronger and stiffer and provides reasonable first crack strength and ultimate strength, whereas the macrofiber is relatively flexible and leads to improved toughness and strain capacity in postcracking zone
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
