Comparative performance analysis of ground slabs and beams reinforced with macro polypropylene fibre, steel fibre, and steel mesh

This study examines the structural performance of concrete slabs and beams reinforced with various types of reinforcement under centrally concentrated loading until failure. Three types of reinforcement were studied, including steel meshes (A142), steel fibers (30 kg/m3), and macro polypropylene (PP) fibers (6 kg/m3). The study discusses the fracture behavior of ground slabs and the enhancement in performance resulting from the inclusion of PP and steel fibers in terms of load–strain and load–deflection responses, deflection profiles, and crack patterns. In addition, the study compared the flexural behavior of fiber-reinforced concrete beams to determine the effectiveness of using various fibers in beams and slabs. The results revealed a significant increase in the flexural strength of steel fiber or steel mesh reinforced slabs on the ground as compared to the reference specimen while slabs reinforced with PP fibers showed favorable results in post-cracking performance and energy absorption compared to steel fibers. The use of PP fibers, steel fibers, and steel meshes can improve the flexural cracking strength of concrete slabs by 28%, 47%, and 79%, respectively. However, predictions based on the beam tests and physical properties of steel mesh overestimated the flexural strength of ground slabs by 12%, while the corresponding predictions of PP fiber-reinforced slabs and steel fiber-reinforced slabs were 45% and 24% higher than the experimental results. This study provides insights into the performance of different types of reinforcements in concrete slabs and beams, which can be valuable in designing and constructing reinforced concrete structures

Effects of Seawater Environment on the Degradation of GFRP Composites by Molecular Dynamics Method

Glass fiber-reinforced polymer (GFRP) composites are promising composites often utilized in coastal infrastructure or used as an alternative to steel reinforcement in seawater sea sand concrete due to their excellent corrosion resistance. Understanding the degradation mechanism of GFRP in corrosion environments is significant for improving the long-term performance of GFRP materials. This paper presented the influences of seawater content and temperature on the properties of GFRP composites using the molecular dynamics method. The simulation results were validated by existing experiments on mechanical properties, interlaminar strength, and microstructures of an accelerated aging test of GFRP. The calculation results indicated that when seawater content of the matrix increased from 0% to 9.09% at 298 K, Young’s modulus, shear modulus, and bulk modulus decreased 46.72%, 53.46%, and 41.75%, respectively. The binding energy of GFRP composites with seawater content of 2.15% at 353 K was 26.46% lower than that of unconditioned GFRP at 298 K. It revealed that the higher seawater content and temperature accelerated the degradation of the GFRP composites. The investigation provided a comprehensive understanding of the degradation mechanism of GFRP in seawater environments and provided a basis for the durability design of GFRP composites

Characterisation of macro polyolefin fibre reinforcement in concrete through round determinate panel test

Macro polyolefin fibres can effectively improve flexural toughness and post-cracking performance of concrete, they are hence becoming popular in various constructions. This research focused on quantifying reinforcing effects of macro polyolefin fibres in concrete using round determinate panel test. Effects of fibre length, fibre dosage and concrete strength on the toughness of fibre reinforced concrete were investigated. A new characterisation method using toughness index was preliminarily attempted to introduce. It reflects the degree to which the fibre changes the toughness of plain concrete. It also "normalises" the toughness into approximately the same magnitude with other flexural tests, making it possible to compare with different flexural tests

Post-cracking performance of recycled polypropylene fibre in concrete

Macro recycled plastic fibre offers significant environmental benefits over virgin plastic fibre and steel reinforcement. However, as there is limited research on performance of recycled plastic fibre in concrete, it has not yet been widely adopted by the construction industries. In this research, post-cracking performance of different kinds of recycled polypropylene fibres from industrial waste was studied and compared with that of virgin polypropylene fibre in concrete. The diamond-indent recycled fibres showed a good balance of tensile strength, Young's modulus and concrete bonding, thus producing brilliant post-cracking performance. This research proved the feasibility of using recycled fibres as reinforcement in concrete footpaths

Tetrathiafulvalene esters with high redox potentials and improved solubilities for non-aqueous redox flow battery applications

The exploitation of high performance redox-active substances is critically important for the development of non-aqueous redox flow batteries. Herein, three tetrathiofulvalene (TTF) derivatives with different substitution groups, namely TTF diethyl ester (TTFDE), TTF tetramethyl ester (TTFTM), and TTF tetraethyl ester (TTFTE), are prepared and their energy storage properties are evaluated. It has been found that the redox potential and solubility of these TTF derivatives in conventional carbonate electrolytes increases with the number of ester groups. The battery with a catholyte of 0.2 mol L−1 of TTFTE delivers a specific capacity of more than 10 Ah L−1 at the current density of 0.5 C with two discharge voltage platforms locating at as high as 3.85 and 3.60 V vs. Li/Li+. Its capacity retention can be improved from 2.34 Ah L−1 to 3.60 Ah L−1 after 100 cycles by the use of an anion exchange membrane to block the crossover of TTF species. The excellent cycling stability of the TIF esters is supported by their well-delocalized electrons, as revealed by the density function theory calculations. Therefore, the introduction of more and larger electron-withdrawing groups is a promising strategy to simultaneously increase the redox-potential and solubility of redox-active materials for non-aqueous redox flow batteries