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.

As a renewable natural plant fiber, Coir fiber (CF) can be used to as an alternative to improve poor toughness and crack resistance of magnesium phosphate cement (MPC), replacing such artificial fibers as steel fiber and glass fiber and thereby reducing huge energy consumptions and large costs in artificial fibers’ production and waste treatment. Aiming at examining the effects of CF volume concentrations on MPC flexural properties, this study employed a typical three-point bending test, including thirty cuboid specimens, to investigate the flexural strength, load-deflection behavior, and flexural toughness of MPC with different CF volume concentrations from 0% to 4% at the curing age of seven days and 28 days. Results demonstrated that CF presented similar effects on MPC’s properties at two curing ages. At both curing ages, as CF grew, flexural strength increased first and then decreased; specimen stiffness, i.e., MPC elastic modulus, displayed a decreasing trend; and flexural toughness was improved continuously. Additionally, modern microtesting techniques, such as, scanning electron microscopy (SEM) and energy dispersive X-ray detection (EDX), were adopted to analyze the microstructure and compositions of CF and specimens for explaining the properties microscopically.

Coir fiber (CF), an eco-friendly and renewable natural fiber, was introduced into magnesium phosphate cement (MPC) mortar to improve its crack resistance. A total of 21 specimens were employed to investigate the failure pattern, compressive strength, stress–strain curve, and energy absorption of MPC with varying CF lengths (0, 5, 10, 15, 20, 25, and 30 mm) after a curing period of 28 days through a static compressive test. The results demonstrated that compressive strength, elastic modulus, and secant modulus decreased with the increase in CF length. However, energy absorption presented a convex curve, which increased to the maximum value (77.0% relative to the value of the specimen without CF) with a CF length of 20 mm and then declined. A series of modern micro-tests were then carried out to analyze the microstructure and composition of specimens to explain the properties microscopically.

Foam concrete, a new kind of building material, has attracted wide attention due to its high energy absorption capability and low density. However, the low strength and poor toughness of foam concrete have become obstacles to hinder its further application. Coir fiber (CF), as a renewable recycled plant fiber, has shown a significant effectiveness for improving the mechanical properties of cement-based materials in some previous studies. In this paper, CF was introduced into foam concrete to develop its dynamic performance. A total of 54 foam concrete specimens with different CF contents (0.0%, 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%) were prepared and divided into six groups. A single-impact test was carried out at three driving gas pressures (0.20, 0.25, and 0.30 MPa) by means of Split Hopkinson pressure bar experimental technology to investigate the effect of CF content on the dynamic performance of foam concrete, including the failure mode, dynamic compressive strength, stress-strain behavior, and energy absorption capacity. Furthermore, to explain the change mechanism of CF-foam concrete, a microstructure analysis was conducted through a scanning electron microscope and X-ray diffraction. The results revealed that an appropriate amount of CF could significantly improve the dynamic performance of foam concrete. The foam concrete’s ductility attained an optimal level at the CF content of 1.5%. The dynamic compressive strengths reached their highest values of 2.27 MPa (at 0.20 MPa gas pressure), 3.18 MPa (at 0.25 MPa gas pressure), and 4.21 MPa (at 0.30 MPa gas pressure) at the CF content of 1.5%. The peak values of energy absorption were 8.9 J (at 0.20 MPa gas pressure) at a CF content of 2.0%, 14.9 J (at 0.25 MPa gas pressure) at a CF content of 1.5%, and 22.4 J (at 0.30 MPa gas pressure) at a CF content of 1.5%, respectively. However, this improvement would deteriorate when CF was in excess.

A new type of pier anti-collision composite structure composed of honeycomb steel and polyurethane (PU) elastomer was proposed in this study. The impacts of the shape and filling materials of inner core cells on the failure mode, load–displacement cure, bearing capacity, structural stability, and energy absorption were studied by conducting uniaxial compression tests on device segments. Test results showed that the bearing capacity, structural stability, and energy absorption of honeycomb steel structure were significantly improved by PU elastomer filling. Besides, when compared with the square honeycomb structure and the regular hexagon honeycomb structure, the maximum values of average load, total energy absorption (TEA), and specific energy absorption (SEA), which were 69.6 kN, 1986.1 J, and 1300 J/kg, respectively, for the regular triangle honeycomb structure without PU filling, increased to 459.3%, 376.38%, and 212.5%, respectively, for the regular hexagonal core cell structure with PU filling, which was proved to be the most suitable core structure for pier anti-collision device.