Coconut Fibre Reinforced Concrete Research Articles

Impact resistance of flax FRP fully wrapped coconut fibre reinforced concrete beams and shear contribution of FRP

This study investigates the behaviour of flax fibre reinforced polymer (FFRP) fully wrapped coconut fibre reinforced concrete (CFRC) beams and FRP contribution to shear strength under impact loadings. Both repeated and single drop-weight tests were carried out on the beams, with a dimension of 500 mm × 100 mm × 100 mm and three different FFRP wrapping thicknesses. For the repeated impact tests, the impact reaction force, deflection histories and FRP strains were recorded and analysed to investigate the influence of FFRP wrapping thickness on the impact resistance. For the single impact tests, the energy absorption, failure modes and the shear contribution of FFRP in CFRC beams was studied. The results showed that the impact resistance of the fully FFRP wrapped beams showed a non-linear increase tendency with thickness. The damage mechanism of concrete beams is also influenced by the FRP thicknesses. The analytical results of shear contribution of FFRP were calculated by considering the dynamic increase factor, which fits well with experimental values, indicating that the proposed method is reasonable.

Renovation Effect of Flax FRP-Reinforced Cracked Concrete Slabs under Impact Loadings

The impact behaviour of flax fibre-reinforced polymer (FFRP) renovated coconut fibre-reinforced concrete (CFRC) slabs was investigated through two series of experiments and theoretical analysis. The first experiment was carried out to find out the effectiveness of FFRP retrofitted method for the partly damaged concrete structure and its performance under impact loadings. The renovation process was applied on the pre-cracked rectangular CFRC slabs of 600 mm × 300 mm × 50 mm with FFRP laminates, before the repeated impact tests. Then, the parameters of these slabs, i.e., impact force history, deflection history and damage pattern, were discussed in detail. Another experiment was conducted on the FFRP-CFRC square slabs with a dimension of 600 mm × 600 mm × 50 mm. Based on test results, the effect of different FFRP configurations was discussed to find out the effective reinforcement method. In addition, the two-degree-of-freedom spring-mass model was applied to predict the impact force. Results demonstrate that FFRP composites have a good potential to be utilised as renovated construction materials under dynamic load conditions.

Effect of Surface Modification and Fibre Content on the Mechanical Properties of Coconut Fibre Reinforced Concrete

In the past few decades, concrete has been the most widely used material for structural applications in the world and uses steel reinforcement as aide to meet the flexural, tensile and ductility demands required of concrete structures. Manufacturing of concrete and steel reinforced concrete structures is associated with millions of tons of carbon dioxide emissions and mineral waste. This activity is also responsible for the depletion of a large number of non-renewable resources. Reinforcing steel is also a high cost material, consumes a lot of energy in its production. Consequently, the use of natural fibres as an alternative for steel reinforcement is widely investigated, to promote the use of sustainable concrete structures. This study aims to investigate the effect on durability, flexural, compressive, tensile properties and workability of concrete by incorporating coir fibre at varying fibre content to find the fibre content which gives optimum results. The fibre contents used were 0%, 0.5%, 1.0%, 1.5% and 2.0% by weight of cement. Furthermore, the effect of modifying the surface of the coir fibres by alkali treatment (i.e. 5 wt.% NaOH solution) and coating the fibres with epoxy paint and polyurethane varnish on coir fibre reinforced concrete (CFRC) were also investigated. Tests conducted on the CFRC specimens included slump test and flexural, compressive and tensile strength tests. Water absorption and sorptivity tests were also conducted to investigate the durability. Slump (workability) and unit weight reduced with an increase in fibre content. The surface modification methods used, had resulted in an increased workability and a reduced unit-weight. A coconut fibre content of 1% produced the best combination of flexural, tensile and compressive properties. Water absorption and sorption rate per unit time, increased with an increase of coir fibre content. It is also found that epoxy paint and alkali treatment of the fibres has a positive effect on the mechanical strength properties and also the durability and workability of the CFRC specimens. However, polyurethane varnish coating had a detrimental effect on the mechanical strength properties of the CFRC specimens.

Dynamic compressive behaviour of coconut fibre-reinforced concrete composite

Coconut fibre-reinforced concrete (CFRC) is widely used in the construction of house walls, especially in rural areas, but its impact resistance has rarely been studied. This paper investigates the dynamic compressive behaviour of CFRC by conducting high-speed servo-hydraulic tests under different strain rates ranging from 0·2 to 30 s−1. To study the strain rate effects on compressive strength, failure pattern, failure processes and energy absorption, CFRC cylindrical specimens with different coconut fibre contents – that is, 1, 3 and 5% of cement mass – were prepared and tested. The results showed that compressive strength increased with the strain rate, but decreased when the coconut fibre volume exceeded 3%. This paper discusses the relationship between the fibre-content-dependent dynamic increase factor and the strain rate for CFRC composites. In addition, it studies the failure process of CFRC via an analysis of the effect of the fibre content. The result of this research should be helpful in designing high-speed, impact-resistant, natural fibre-reinforced composites.

A Feasibility Study on partially substituted Coarse Aggregate with Oil Palm Shell in Coconut Fiber Reinforced Concrete

In the search of alternative materials for the replacement of conventional coarse aggregate, the feasibility of utilizing agricultural waste products was looked into in the effort of producing a more environmentally friendly and less dense concrete. Mechanical properties of partially substituted coarse aggregates using oil palm shell (OPS) in a concrete composite reinforced with a low volume fraction of coconut fibre (CF) have been studied for its feasibility as an alternative solution to the problem. Analysis on the impact of compressive strength, flexural strength, density and Young’s modulus have been conducted on hardened coconut fibre reinforced concrete (CFRC) at 15% and 25% substitution by volume of conventional coarse aggregates with OPS. The properties of the composite concrete were evaluated with reference to the control sample, CFRC reinforced with 0.2% fibre volume fraction. The results have shown that it is feasible to produce a sustainable grade 30 concrete of lower density with CFRC at 25% level of OPS substitution.

Experimental and theoretical studies of flax FRP strengthened coconut fibre reinforced concrete slabs under impact loadings

The impact behaviour of flax fibre reinforced polymer (FFRP) strengthened coconut fibre reinforced concrete (CFRC) slabs was investigated through experimental and theoretical studies. Plain concrete, CFRC and FFRP-CFRC slabs were built and tested under impact loadings. Impact results showed FFRP-CFRC specimens had better performance in aspects of energy absorption and keeping the integrity of the concrete, comparing with PC and CFRC specimens. Another impact test was carried out for finding the more effective wrapping configuration between three different wrapping designs of the FFRP strengthened CFRC slab, and their parameters, i.e. impact force history, strain history of FFRP, deflection history, energy absorption and damage pattern were discussed to evaluate the impact resistance. After the experimental study, theoretical analysis method was used to predict the maximum impact force as well as the maximum deflection, the results of which showed good agreement with the experimental results.

Mechanical Properties and Fracture Behaviour of Coconut Fibre Reinforced Concrete (CFRC)

The effect of coconut fibre content on the mechanical properties and fracture behavior of reinforced concrete was studied. The mix design used for the plain concrete and the coconut fibre reinforced concrete was based on 1:2:4 for cement: sand and coarse aggregate. Water/cement ratio used was 0.6. The coconut fibre was added as reinforcement principally to check the propagation of cracks. The composites developed by adding 6%, 8%, 10% and 12% coconut fibre (by weight) , mixing and curing. Plain concrete was cats and cured and used as control. Composites were cured for 7, 14 and 28 days. It was observed that the composite with 6% of coconut fibre demonstrated the highest compressive, flexural and split tensile strengths when compared to the control.

Behaviour of CFRC beams strengthened by FFRP laminates under static and impact loadings

This paper investigates the impact resistance of a new construction material, being coconut fibre reinforced concrete (CFRC) beams strengthened with flax fibre reinforced polymer (FFRP) laminates. To study the impact resistance of the material, a series of CFRC specimens with various FFRP thicknesses (2-, 4- and 6-layer) were experimentally studied through static and drop weight impact tests. Parameters of the FFRP-CFRC beams, i.e. the impact force, deflection, energy absorption, dynamic increase factor (DIF) and damage pattern were studied. In addition, the influence of the FFRP laminate thickness was investigated in terms of (1) flexural strength and toughness under static loading, (2) flexural behaviour under impact loading, and (3) failure mode. The results showed that FFRP laminates were effective in enhancing the flexural strength under both static and impact loadings. It is also suggested that FFRP-CFRC composites could be used as environmentally-friendly materials for protective structures in resisting impact loadings.

Flexural behaviour of FFRP wrapped CFRC beams under static and impact loadings

The flexural behaviour of a new construction material, flax fibre reinforced polymer (FFRP) wrapped coconut fibre reinforced concrete (CFRC) beams, under static and impact loads was investigated for the first time. Coconut fibre was mixed into concrete and the concrete beams were wrapped externally with flax fibre reinforced polymer (FFRP) laminates. Then static tests, followed by single and repeated impact tests were performed. Three different fibre contents, i.e. 1%, 3% and 5% of cement mass, corresponding to fibre volumes of respectively 0.4%, 1.2% and 2%, were considered. The effect of the coconut fibre content on the dynamic flexural load, deflection, energy absorption and dynamic increase factor (DIF) were analysed to discover the composites impact properties. The test results indicated that the flexural strength of the FFRP-CFRC beams was almost three times higher than that of CFRC beams. Dynamic increase factors (DIFs) of the FFRP-CFRC beams were found not very sensitive to the coconut fibre content but influenced by strain rate. The beams with 3% coconut fibre content were the best in resisting impact when compared with that of FFRP-CFRC beams with 1% and 5% coconut fibre content.

The behaviour of coconut fibre reinforced concrete (CFRC) under impact loading

This work presents the behaviour of coconut fibre reinforced concrete (CFRC) composites under drop weight impact loadings. Both single and repeated impact tests were conducted using a drop weight device. Both plain concrete (PC) and CFRC cylinders with the identical size of 200mm×100mm were tested. Various impact energies were applied to the specimens by adjusting the drop height. In the single impact test, the history of impact force, change of Young’s moduli and the dynamic increase factor (DIF) of CFRC were investigated. The damage pattern of PC and CFRC was compared. In the repeated impact tests, the effect of impact height on the maximum compressive stress and the damage pattern was evaluated. The relationship between impact height and maximum impact stress was examined and an empirically derived equation was proposed.

Compressive behaviour of flax FRP double tube confined coconut fibre reinforced concrete

The use of natural fibre reinforcement in polymer and concrete composites has in recent years attracted significant research interest. When coconut fibre reinforced concrete (CFRC) is confined by flax fibre reinforced polymer (FFRP), the strength of FFRP-CFRC composite is significantly enhanced. While researchers have studied the effect of FFRP confinement on compressive strength, their work has mainly focussed on the outside confinement of CFRC. In contrast, this study considers a double confinement, i.e. CFRC is confined respectively by large and small FFRP tubes both externally and internally. The experimental results show that in comparison with single confinement, double confinement enhances the axial compressive strength and strain of the FFRP-CFRC composite, even though less concrete is used.

Use of coconut fibre reinforced concrete and coconut-fibre ropes for seismic-resistant construction

Earthquake-resistant and economical housing is the most desirable need in rural areas of developing countries. These regions often suffer significant loss of life during a seismic event. To enable an efficient and cost-effective solution, a new concept of construction, i.e. a wallette of interlocking blocks with movability at the interface and rope reinforcement, is investigated. The novel interlocking block is made of coconut fibre reinforced concrete (CFRC). The reason for using coconut fibre is their highest toughness amongst natural fibres. This paper describes the in-plane behaviour of the interlocking wallette under earthquake loadings. The wallette response is measured in terms of induced acceleration, block uplift, top maximum relative displacement and rope tension. The applied earthquake loadings cannot produce any damage in the structure, i.e. blocks and/or ropes. The response of the wallette is explained in detail along with correlation of materials aspect with structural behaviour.

Residual compressive and shear strengths of novel coconut-fibre-reinforced-concrete interlocking blocks

The results of an experimental study to evaluate the residual compressive and shear strengths of novel coconut-fibre-reinforced-concrete (CFRC) interlocking blocks are discussed in this paper. This work is part of a research project in which the development of mortar-free interlocking structures is intended for cheap and easy-to-built earthquake-resistant housing. Recently, mortar-free walls made of these blocks were tested under a series of harmonic and earthquake loadings. Only few blocks at the wall bottom were damaged, the other blocks (with no visual damage) had gone under numerous uplifts which might have affected the block strengths. In parallel, the blocks without any use over a period of time in tropical environment are also considered as coconut fibres are natural materials whose strengths might have decayed. These two cases represent two real scenarios in which (I) a structure stands without having an earthquake over a period and (II) a structure having a series of dynamic loading. In both cases, the residual strengths are of much interest to determine the remaining serviceable life of the structures. The results show that the impact of dynamic load histories on capacities of CFRC interlocking blocks was relatively more in comparison to the effect of age. The compressive and in-plane strengths were increased up to 3.2% and 5.7%, respectively, after undergoing a series of dynamic loading. This shows the advantage of earthquake loading on mortar-free structures.

Experimental Investigation of Flax FRP Tube Confined Coconut Fibre Reinforced Concrete

The compressive and flexural performance of flax fibre reinforced polymer (FFRP) confined coconut fibre reinforced concrete (CFRC) structures were investigated. The mass content of coconut fibre considered was 1% of cement. Eighteen cylinders were tested under uniaxial compression and 12 beams were tested under four-point bending. Test results show that in compression, both FFRP tube and FFRP wrapping confinements enhance the axial compressive strength and ultimate strain of concrete significantly, e.g. the ultimate strength of 4-layer FFRP tube confined CFRC is 94% larger than that of the unconfined CFRC. In flexure, the FFRP tube increases the lateral load bearing capacity and the deflection several times larger than the unconfined concrete columns, e.g. the ultimate lateral load of 4-layer FFRP confined PC and CFRC are 1066% and 946% larger than the corresponding unconfined PC and CFRC specimens. In flexure, coir inclusion can affect the failure mode of the FFRP-CFRC composite structure significantly.

Experimental investigations on coconut-fibre rope tensile strength and pullout from coconut fibre reinforced concrete

► The rope tensile strength and rope pullout from concrete is investigated experimentally. ► Load–slippage curves are obtained from the rope pullout tests. ► The stress–strain curves of the coconut-fibre ropes are obtained. ► Empirical equations are proposed for tensile and bond strength. ► The increased tensile and bond strength is achieved with boiling treatment. The utilisation of coconut-fibre ropes as vertical reinforcement in mortar-free interlocking structures is under consideration for use in cost-effective earthquake-resistant housing. The walls are intended to be constructed with novel interlocking blocks, and coconut fibre reinforced concrete (CFRC) is used as a construction material (presented in a separate study). The rope anchorage is achieved by embedding it in the foundation and top tie-beams. The bond between the rope and the CFRC plays an important role, and the rope tensile strength is also significant in the overall stability of the proposed structure. The rope tension generated due to earthquake loading should be less than both the pullout force and the rope tensile load to avoid the structure collapse. As a pilot study, the scope of the current work is limited to the axial pullout behaviour and tensile capacity of the rope. Therefore, the bond strength between the rope and CFRC, and the energy required to pull out ropes from CFRC are investigated experimentally using rope pullout tests. The factors considered include rope embedment length, rope diameter, pre-treatment condition, concrete mix design ratio, fibre content and knot in the material matrix. The tensile strength and elongation of coconut-fibre ropes were determined considering the parameters of rope diameter and pre-treatment. To increase the pullout energy, bond strength and tensile strength of the rope, the boiling treatment was found to be beneficial compared to chemical treatment. The pullout energy increases with an increase in embedment length, rope diameter, cement and fibre content in the matrix. With the knowledge obtained, empirical equations are proposed to determine the pullout energy, bond strength and tensile strength of the rope.

Mechanical and dynamic properties of coconut fibre reinforced concrete

Coconut fibres have the highest toughness amongst natural fibres. They have potential to be used as reinforcement in low-cost concrete structures, especially in tropical earthquake regions. For this purpose, the mechanical and dynamic properties of coconut fibre reinforced concrete (CFRC) members need to be well understood. In this work, in addition to mechanical properties, damping ratio and fundamental frequency of simply supported CFRC beams are determined experimentally. A comparison between the static and dynamic moduli is conducted. The influence of 1%, 2%, 3% and 5% fibre contents by mass of cement and fibre lengths of 2.5, 5 and 7.5cm is investigated. To evaluate the effect of coconut fibres in improving the properties of concrete, the properties of plain concrete are used as a reference. Damping of CFRC beams increases while their fundamental frequency decreases with structural damage. CFRC with higher fibre content has a higher damping but lower dynamic and static modulus of elasticity. It is found that CFRC with a fibre length of 5cm and a fibre content of 5% has the best properties.