Effects of kenaf bast fibres on hydration behaviour of cement

The compatibility between cement and kenaf bast fibre and its improvement with various types of accelerators were investigated by observation and analysis on hydration behaviour in terms of hydration characteristics, namely, maximum hydration temperature and required time to reach maximum temperature. Five extraction methods (crude, water retting, decortication, NaOH retting and benzoate retting), four accelerators (CaCl2, AlCl3, Na2SO4, CaO), three concentrations (2, 4 and 6%) and three particle sizes (0.5, 0.8 and 4.0 mm) were used. The hydration behaviour of mixtures demonstrated that NaOH and benzoate were unsuitable with cement. Meanwhile, CaCl2 and CaO were found to be effective accelerators for restraining inhibitory influences. In addition, 2% accelerator was available and acceptable for quick-curing cement. Particle sizes of 0.5 and 0.8 mm required addition of accelerators to reach maximum cement setting

Physical-mechanical characteristics of cement-bonded kenaf bast fibres composite boards with different densities

This study was carried out to explore the potential of kenaf bast fibres (KBFs) for production of cement-bonded kenaf composite boards (CBKCBs). More than 70% of the KBFs were of size >3.35 mm and length of 31±0.4 mm, therefore, they were used for CBKCBs production. The CBKCBs with the dimensions of 450 × 450 × 12 mm were produced using cement (C): KBF with proportion of (2:1) and different board densities (BD) namely 1100, 1300 and 1500 kg/m3The CBKCBs were first cured in a tank saturated with moisture for 7days, and then kept at room temperature for 21 days. Mechanical and physical properties of the CBKCBs were characterized with regards to their modulus of rupture (MOR), modulus of elasticity (MOE), internal bond (IB), water absorption (WA), and thickness swelling (TS). Results of the tested CBKCBs revealed that the MOR increased while the MOE decreased due to uniform distribution of KBFs. It was found that loading of KBFs has a negative influence on the internal bond (IB) of the CBKCBs; the IB was reduced as KBFs tend to balling and making unmixed aggregates with the cement. These results showed that the CBKCB is a promising construction material that could potentially be used in different structural applications due to their good mechanical characteristics

Retting process of some bast plant fibres and its effect on fibre quality : a review.

Retting is the main challenge faced during the processing of bast plants for the production of long fibre. The traditional methods for separating the long bast fibres are by dew and water retting. Both methods require 14 to 28 days to degrade the pectic materials, hemicellulose, and lignin. Even though the fibres produced from water retting can be of high quality, the long duration and polluted water have made this method less attractive. A number of other alternative methods such as mechanical decortication, chemical, heat, and enzymatic treatments have been reported for this purpose with mixed findings. This paper reviews different types of retting processes used for bast plants such as hemp, jute, flax, and kenaf, with an emphasis on kenaf. Amongst the bast fibre crops, kenaf apparently has some advantages such as lower cost of production, higher fibre yields, and greater flexibility as an agricultural resource, over the other bast fibres. The fibres produced from kenaf using chemical retting processes are much cleaner but low in tensile strength. Enzymatic retting has apparent advantages over other retting processes by having significantly shorter retting time and acceptable quality fibres, but it is quite expensive

Properties of kenaf bast fibre cement composite board

Kenaf bast fibre (KBF) is rich in cellulose and, has high tensile strength, which is suitable for reinforcement of cement-bonded board. This study used kenaf bast fibre as partial replacement for cement as well as reinforcement for cement board. The work comprised the evaluation of mechanical and physical properties of kenaf bast fibre which were separated using different extraction methods (water, decortication and chemical), hydration behaviour, and the effects of different board formulations on the properties of cement-bonded kenaf board (CBKB). The objectives of the study were: 1) to evaluate the effects of fibre separation method on the physical, chemical and mechanical properties of kenaf bast fibre, 2) to determine the effect of incorporation of kenaf bast fibre, accelerators (calcium chloride (CaCl2), aluminium chloride (AlCl3), sodium sulfate (Na2SO4) and calcium oxide (CaO2)) and additives (silica fume and superplasticiser) on the hydration properties of Portland cement, 3) to evaluate the mechanical properties and dimensional stability of cement-bonded kenaf board, 4) to examine the curing behaviour of cement-bonded kenaf board, and 5) to characterize the permeability , surface and thermal behaviour of cement-bonded kenaf board. The performance of different CBKB densities was evaluated based on the strength – modulus of rupture (MOR), the stiffness – modulus of elasticity (MOE) and internal bonding (IB). The dimensional stability was assessed by determining the percentage of water absorption (WA) and thickness swelling (TS). The morphological properties of kenaf bast fibre were found to be significantly affected by the extraction methods used. Using sodium hydroxide (NaOH) for retting reduced the fibre lumen diameter and increased the cell wall thickness significantly. Both benzoate- and water-retted fibres experienced the same but at a much lesser effect. Mechanical decortication however was found to excessively reduce the cell wall thickness much thinner than the crude (unprocessed) fibre. There was a small increment in fibre density for NaOH-retted and benzoate-retted bast fibres over those of water, decorticated and crude (control). The densified fibre may be contributed by the amount of chemicals being absorbed into the fibre. Among the different extraction methods used, decorticated, water and NaOH-retted fibres have significantly higher tensile strengths. The hydration test suggests that NaOH and benzoate were not suitable for the kenaf retting. Both NaOH- and benzoate-retted fibres had relatively higher pH hydration time and low maximum hydration temperature which is not conducive for curing of cement-bonded kenaf board. Both water-retted and decorticated KBF had good hydration properties, and suitable for cement board production. The suitable fibre size is > 3.5 mm. Fibres with smaller size apparently require the addition of accelerators to enhance their compatibility. Among the different accelerators used, CaCl2, AlCl3, Na2SO4 and CaO, both CaCl2 and CaO proved to be the best with their optimal concentration at 2%. Between the two additives used, silica fumes (SF) and superplasticiser (SP), the former was found to be a better choice based on it is hydration properties. Among the methods of fibre separation, water retting and decortication produced fibres of good quality, high tensile strength, good hydration properties, good fibre morphology and high cellulose content. Incorporation of KBF in cement-bonded board generated reasonably light and strong panel, however, the IB was reduced significantly. The main reason for this is the separation of kenaf fibres from cement creating a weak inter-particle bonding within the board. Almost all the failures were observed to occur at the interface. Adding SF at 7% improved the IB by 83%. The presence of board density also has a negative effect on the mechanical properties and the dimensional stability of the boards. Among the three cement: KBF proportions (2:1, 2.5:1 and 3:1) used in this study,using 2:1 resulted in boards with the best performance in terms of MOR, MOE, WA and TS. The best combination to produce acceptable performance CBKB is by using decorticated KBF, at 2:1 (cement: KBF), 7% SF and board density (1100 kg/m3). The properties: MOR (10.9 MPa), MOE (5061 MPa), IB (0.15 MPa), WA after 2h and 24h (23.7 and 27%, respectively), TS after 2 and 24h (0.87 and 3.01%,respectively

Effect of fiber extraction methods on some properties of kenaf bast fiber

The objective of this study was to investigate the effect of different extraction methods on the fiber morphology, density, chemical composition and tensile strength of kenaf bast fiber. Kena fbast fibers were extracted using different methods (crude, decorticated, water retted, 5% sodium hydroxide retted and 5% benzoate retted) and their physicochemical characteristics were investigated. The morphological characteristics showed a significantly reduced lumen diameter and increased cell wall thickness after treated with NaOH at 5%. On the other hand, increased lumen diameter and a decreased cell wall thickness were observed with the decorticated and water retted bast fibers. A slight increase in fiber density was observed for NaOH and benzoate retted bast fibers indicating cell wall densification. Interestingly, the extraction methods used in this study produced bast fibers with high cellulose content and low sugar and starch due to the removal of wax, oil, pectin and hemicelluloses. Regarding the tensile strength, the water retted bast fibers showed highest tensile strength (426.05 MPa), while there was one no difference between decorticated and NaOH retted fibers (386.83 and 393.03 MPa, respectively)