Axial strength and deformability of concrete confined with natural fibre-reinforced polymers

Abstract

This paper presents the results of an experimental study on the compressive behaviour of concrete confined by natural fibre-reinforced polymer (NFRP) jackets which are formed by embedding sisal fibres in an epoxy resin matrix. The sisal fibres are one of the cost-effective materials for use in seismic strengthening applications where a moderate increase in strength and ductility is required. This study has two main objectives: the first is to investigate the effectiveness of NFRP composites in increasing the strength and deformability of confined concrete. For the second objective, the performance of existing strength models developed for conventional synthetic fibre-reinforced polymers is assessed. For this, 36 concrete specimens were tested under uni-axial compression. The study parameters covered the NFRP thickness, concrete strength and cross-sectional shape. Test results indicated that the NFRP confinement is significantly effective in increasing the strength and deformability of confined concrete. Furthermore, it is found that none of the existing considered models is capable of accurately predicting the ultimate strength and strain of NFRP-confined concrete. Finally, new strength models are proposed to predict the compressive strength of circular and square sections. The strengths predicted by the proposed models are found to have a good agreement with experimental results.

Performance of Concrete Confined with a Jute–Polyester Hybrid Fiber Reinforced Polymer Composite: A Novel Strengthening Technique

“…The JPFRP shell failed in a straight continuous crack from top to bottom, parallel to the direction of axial compressive stress and perpendicular to the alignment of the JPFRP confining layers, as shown in Figure 8. A similar failure pattern has been previously reported in the literature [36,37]. When the concrete core cracked, the confinement of the JPFRP laminate had activated and effectively resisted the lateral expansion.…”

“…Supporting our results, Refs. [26,36,55] also reported this type of failure for different types of FRP confined square specimens. Figure 9 shows the failure modes of low-and high-strength square specimens.…”

“…The selected stress-strain models for circular and non-circular columns are given in Tables 8 and 9, respectively. These include the models of [18,36,48,49,55,58,59,61,65,[68][69][70][71]. Huang et al [49] proposed a stress-strain model by using the experimental results obtained from circular polyester FRP-wrapped concrete specimens.…”

“…Therefore, nowadays, efforts have been made to replace the conventional composite materials, i.e., C/GFRP, with alternate materials for civil infrastructure applications, to gain economic and environmental benefits. Studies were conducted on the use of economical and environmentally friendly fibers including hemp [34,35], sisal [36][37][38], jute [36,37,39], coir, and flax [33,40]. Previous studies exemplify that natural fibers have high potential in the reinforcement of the cement matrix [33][34][35][36][37][38][39][40].…”

“…In another study, Sen and Reddy [37] highlighted that jute and sisal fiber could significantly enhance the load-bearing capacity as well as energy absorption of concrete columns. Pimanmas et al [36] investigated the ultimate axial strength and deformability of small-scale low and high-strength circular and square concrete specimens confined with locally manufactured sisal fiber. The study revealed that the enhancement in axial compressive strength and the axial strain was more significant in low strength circular concrete columns as compared with square columns.…”