Abstract
Coir fiber (CF), a renewable natural plant fiber, is more competitive in improving poor toughness and crack resistance of magnesium phosphate cement (MPC) than artificial fibers, due to its slight energy consumptions and low costs in production and waste treatment. In this paper, a typical three-point bending test was carried out to study the effects of CF length on MPC flexural properties. A total of forty-two cuboid specimens were employed to investigate the flexural strength, load-deflection behavior, and flexural toughness of MPC, with CF lengths varying from 0 to 30 mm at the curing age of 7 days and 28 days. Results showed that, at both two curing ages, MPC flexural strength first increased with CF length increasing, and then deceased when CF length exceeded the threshold. However, with the increase of CF length, MPC flexural toughness increased continuously, while MPC elastic modulus displayed a decreasing trend. Additionally, Modern micro testing techniques, such as scanning electron microscope (SEM) and X-ray diffraction (XRD), were also used to study the microstructure and phase compositions of specimens for further explaining the themicroscopic mechanism.
Highlights
Magnesium phosphate cement (MPC), as a new inorganic cementitious material, has great potential in rapidly repairing roads, bridges, and airstrips, due to its advantages of fast setting, high early strength, good durability, and perfect fire resistance [1,2]
Reis et al [9] found that coconut fiber reinforced concrete (CFRC) had greater flexural strength than other natural fiber reinforced concrete
For group T7, specimens presented a typical brittle failure when they were not mixed with Coir fiber (CF)
Summary
Magnesium phosphate cement (MPC), as a new inorganic cementitious material, has great potential in rapidly repairing roads, bridges, and airstrips, due to its advantages of fast setting, high early strength, good durability, and perfect fire resistance [1,2]. Its drawbacks in toughness and crack resistance severely restrict the application of MPC in practical repair works [3,4]. Given the severe environmental problems (such as global warming) and high repair work costs introduced by artificial fiber applications, it is very significative to find out a renewable and low-cost fiber to replace artificial fibers. Reis et al [9] found that coconut fiber reinforced concrete (CFRC) had greater flexural strength than other natural fiber reinforced concrete. Sekar et al [10] found that the flexural strength of Materials 2020, 13, 3692; doi:10.3390/ma13173692 www.mdpi.com/journal/materials
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