In this work, the potentials of Bambusa vulgaris grown in southeast Nigeria for the manufacture of wood-cement composite panels were studied. Representative culms of Bambusa vulgaris were collected from a 4-year-old stand at lower Anambra river basin, southeast, Nigeria. Fiber morphological properties and proximate chemical analysis were determined in accordance with the provisions of the Technical Association of the Pulp and Paper Industries (TAPPI, 1998). Fiber slenderness ratio was 160.95:1, component solubility of 3.09, 5.60, and 19.8 percent for cold water soak for 24 hrs; hot water soak at 80°C for 1 hr, and 1% NaOH soak for 24 hrs respectively. Composite panels were made at 1200 kg/m3 and 800 kg/m3 density levels with flakes of different soak treatments (untreated/control; cold water soak for 24 hrs; water at 80°C soak for 1 hr and 1% NaOH soak for 24 hrs) at variable cement/B. vulgaris mix ratios (1:1, 1.5:1, 2:1, 2.5:1 and 3:1 wt/wt) with 3% CaCl2 as accelerator applied to the wood furnish before cement mixing. Prepared furnish was subjected to initial pre-pressing of 0.5 N/mm2 and final consolidation of 1.4 N/mm2 retained for 24 hrs. Panels were sampled and tested after 28 days for Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) in bending and for water absorption (WA) and thickness swelling (TS) due to a 24-hr water soak. Test was in accordance with provisions of American Standard for Testing of Materials (ASTM-1998). Properties ranged from a low of 25.00 to 75.45 N/mm2 for MOR; 4128 to 15,065 N/mm2 for MOE; 15.01 to 36.11 percent for WA and 3.04 to 12.72 percent for TA. Effect of production mix on properties was determined using factorial analysis. Except for composite density whose effect was not significant at 0.05% level, all production mix was found significant at 0.01% level at the second order level of interactions. All panels met minimum property requirements of American National Standard Institute 208-2-1994 and 208-1-1993, British Standard (BS 5669, 1979) and Malaysian Standard (MS 934, 1984).
Concerns for global environmental degradation as a result of deforestation and use of fossil fuels as well as reported pockets of deficit in supply of forest timber based industrial fiber in some parts of the world have created a need for the search for alternative products that are both sustainable and environmentally friendly [
In general, properties of wood/lignocellulosic composite panels are known to have high correlations with the characteristics of the constituent raw materials, their distribution within the matrix and interactions of the relevant production variables [
Available records indicate that there are over 1200 species of bamboo found in 70 genera [
Presently the use of bamboo in the production of industrial products in Nigeria and indeed sub-saharan Africa is in its infancy. There are obstacles in the production and utilization of wood cement composites. One of such obstacles is the adverse effects of some wood constituents, notably extractives and soluble polysaccharides on the hydration and curing of cement [
The objective of this study were to evaluate the effects of cement/Bumbusa vulgaris mix ratios, chip/flake soak treatments and composite panel densities on the Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) in Bending; and the water absorption and thickness swelling properties of the resultant composite panel.
Representative culms of Bambusa vulgaris were obtained from a four year old bamboo stand at Nteje (6˚16"N latitude and 6˚40"E longitude) in Oyi Local Government Area, Anambra State, southeast, Nigeria. The culms were collected at 10, 20, 50, 70 and 90 percent of the full length for each stick of bamboo. Identification was done using floral parts after the method reported by some authors [
Representative samples of the flakes were either marked and used untreated, to be used after soaking in distilled water for 24 hrs at room conditions; soaked in distilled water at a temperature of 80˚C or soaked in one percent Sodium Hydroxide solution (NaOH) for 24 hrs at room conditions. At the end of each soak treatment, the leachants were allowed to drain off and the flakes washed immediately with copious supply of distilled water. The soaked and unsoaked particles were conditioned in a conditioning chamber at 20˚C ± 2˚C and 65% ± 1% Relative humidity (R. H.) and stored in vapour impermeable bags ready for use.
Proximate chemical analysis was conducted in compliance with the provisions of the standard Test Methods of the Technical Association of the Pulp and Paper Industry [
Representative flakes were selected and reduced to splinters. The splinters were macerated/pulped in 1% NaOH conc. at 80˚C for 10 hrs. At the end of the above period, the resultant fiber bundles were washed in distilled water and the fiber suspension subsequently subjected to further defiberization in the presence of glass beads with the aid of vigorous agitation (Onuorah, 2005). One hundred and thirty (130) representative fiber samples were selected, stained with safarin-C and mounted on slides and viewed at 100× magnifications using a microscope. The fiber dimensions (length, diameter, lumen width and cell wall thickness) were measured wet with the aid of stage and occular micrometer scales [
Thirty representative culms were taken and the culm lengths, culm diameter and culm wall thickness measured using linear tapes and micro gauge. The specific gravity was determined in accordance with the provisions of ASTM D2395-89 [
Appropriate quantity (oven dry weight basis) of the B. vulgaris flakes for each soak treatment type was measured out based on cement-bamboo flakes mix ratio. The exact quantity to be used for each board type was determined in preliminary studies which took into cognizance the soak treatment type/mix ratio/composite density combinations. The required quantity of water in litres (Q) needed for the production of each board was determined using Equation (1)
where C = cement wt in kg; M = fiber/flake moisture content and W = oven dry wt of fiber/flakes as reported by Erakhrumen [
The production constants were as follows: (all pressing was done cold i.e. absence of external heat)
1) Prepressing pressure of 0.5 N/mm2 before final consolidation.
2) Final press pressure of 1.4 N/mm2 for 24 hrs.
3) Curing of the pressed composite took place inside a vapour impermeable bag over a 28-day period.
4) Use of 6 mm thick metal stops placed on opposite sides of the metal caul/formed furnish.
5) Addition of 3% of calcium chloride (wt/wt cement basis) to weighed flakes before addition of cement.
6) Use of 19 mm plywood covered with thin polythene as the top platen.
Mixed furnish for each composite panel was formed on top of a metal cual whose surfaces had been previously covered with a thin polythene sheet while the top of the formed furnish was covered with 19 mm plywood whose surface had been covered with same polythene. Opposite each side of the length of the caul carry-
. Design of variable production mix used in the manufacture of cement—Bambusa vulgaris composite panels
Density kg/m3 | Soak treatmenta | Cement—B. vulgaris flake mix ratiok | ||||
---|---|---|---|---|---|---|
1:1 | 1:5 | 2:1 | 2:5:1 | 3:1 | ||
No of boards produced | ||||||
1200 | Control | 2 | 2 | 2 | 2 | 2 |
1200 | Cold water | 2 | 2 | 2 | 2 | 2 |
1200 | Hot water | 2 | 2 | 2 | 2 | 2 |
1200 | 1% NaOH | 2 | 2 | 2 | 2 | 2 |
800 | Control | 2 | 2 | 2 | 2 | 2 |
800 | Cold water | 2 | 2 | 2 | 2 | 2 |
800 | Hot water | 2 | 2 | 2 | 2 | 2 |
800 | 1% NaOH | 2 | 2 | 2 | 2 | 2 |
kTwo composite panels were made per production mix from which two test specimens per panel were sampled for testing. Control = unsoaked flakes; cold water = unheated distilled water used for soaking the flakes for 24 hrs at room conditions; hot water = flakes soaked in hot water at 80˚C for one hour; 1% NaOH = flakes soaked in 1% concentration of NaOH for 24 hrs at room conditions; aExcept for the control all soak treatments were immediately followed by rapid but instantaneous washing in water in order to remove leachants and/or unspent chemicals.
ing the furnish but besides the furnish was placed a 6 mm metal stop. At the end of the curing period the panels were trimmed 0.5 mm from the edges in order to remove areas that were not properly consolidated during pressing.
The composite panels were sampled and tested in accordance with the provisions of ASTM D1037-96 [
Properties tested were the Modulus of Rupture (MOR) and Modulus of Elasticity (MOE) in Bending; the water absorption (WA) and thickness swelling (TS) due to a 24 hours horizontal water soak. There were a total of 4Nos tests for each production mix thus making a total of 160 Nos tests for each property. The reported properly value represents weighted average of four test samples at each production mix (mix ratio/soak/density interaction).
A complete randomized experiment was designed at which the effects of the variable production mix (5 Nos mix-ratios, 4 Nos soak types and 2 Nos composite densities) and all possible interactions were determined. The levels of significant effects of the main variables, their first order interaction and second order interaction were determined using factorial analysis [
. Fiber characteristics and proximate chemical analysis of B. vulgaris (bamboo) grown in Anambra river basin, southeast, Nigeria as compares with other non wood and wood-based fiber sources used in composite industry
S/N | Property | B. vulgaris used in the study | Bambooes globally | Sugar cane bagasse | Deciduous hardwoods | Coconut coir |
---|---|---|---|---|---|---|
A. | Fiber dimensions | |||||
i. | Fiber length (mm) | 2.91 (0.072) | 1.360 - 4.030 | 1.7 | 1.25 | 1.0 |
ii. | Fiber dimeter (μm) | 18.08 (1.68) | 8.0 - 30.0 | 20 | 25 | 10 - 20 |
iii. | Lumen width (μm) | 10.04 (1.3) | = | = | = | = |
iv. | Cellwall thickness (μm) | 3.98 (0.27) | = | = | = | = |
v. | Slenderness ratio | 160.95:1 | 135 - 175:1 | 85:1 | 50:1 | = |
vi. | Culm diameter (cm) | 10.65 (0.78) | = | = | = | = |
vii. | Culm wall thickness (cm) | 1.8 (0.43) | = | = | = | = |
viii. | Chem. length | 30.43 (1.65) | = | = | = | = |
ix. | Bamboo specific gravity | 0.68 (0.08) | = | = | = | 1.15 |
B. | Proximate chemical analysis | |||||
i. | Cold water solubility (%) | 3.09 (0.18) | = | 3.42 | = | = |
ii. | Hot water solubility (%) | 5.60 (0.52) | 4.4 | 7.42 | 5.25 | |
iii. | 1% NaOH solubility (%) | 19.8 (0.91) | = | 32.2 | ||
iv. | Alcohol benzene (1:2 v/v) | 5.0 (0.70) | 3.2 | 1.85 | = | 3.0 |
v. | Ash (%) | 2.51 (0.36) | 1.7 - 5.3 | 1.5 - 5 | <1.0 | 2.22 |
vi. | Silicon (%) | = | 1.5 - 3 | 0.7 - 3 | <1.0 | = |
vii. | Pentosan (%) | 17.12 (0.33) | 15 - 26 | 27 - 33 | 19 - 26 | = |
viii. | Cellulose (%) | 53.64 (0.87) | = | = | = | 43 |
ix. | Hellocellulose (%) | 62.9 | 57 - 66 | 49 - 62 | 54 - 61 | = |
x. | Lignin (%) | 25.88 (0.43) | 21 - 31 | 19 - 24 | 23 - 30 | 45 |
(1) Fiber Dimensions are the weighted average of 130 fiber measurements. (2) Information on deciduous words and other non wood species used in this table are from Hunter (2001) and Asasutjarit (2005).
morphological properties and the density of the bamboo compare favourably with those of other woody and non-wood species used in the production of wood-cement composites in other countries. Of particular interest is the fiber slenderness ratio of 160.95:1 which is within the range of 135 to 175:1 reported for all species of bamboo [
The proximate chemical analysis results are also in
At any given cement—B. vulgaris mix ratio (1:1, 1.5:1, 2:1, 2.5:1 and 3:1 wt/wt) and soak treatment (control, cold water, hot water and 1% concentration of NaOH) the MOR increased as the ratio of the cement in the composite was increased (
The effects of Board density on the MOR of the composite panel was not found significant at 0.05% level of probability in a factorial analysis. This was not expected as high density implies higher compaction ratios for each given production mix (mix ratio and soak type). However, it is widely acknowledged that there is optimal compaction ratio above which further improvements in wood based composite properties as a result of compaction ratio no longer results in significant properties improvements [
At any given composite panel density and cement: B. vulgaris flakes mix ratio, the composite MOE in bending increased as the soak treatment was changed from unsoaked flakes/control to cold water soak to Hot water soak to 1% concentration of NaOH soak in that order (
. Properties of Bambusa vulgaris (bamboo)—cement composite panels as affected by variable production mix
Soak treatment | Cement— B. vulgaris mix ratio (wt/wt) | Composite panel density kg/m3 | Mechanical properties | Physical properties | ||
---|---|---|---|---|---|---|
Modulus of rupture N/mm2 | Modulus of Elasticity N/mm2 | Water absorption due to 24 hrs soak (%) | Thickness swelling due 24 hrs water soak (%) | |||
Control | 1.0:1 | 1200 | 28.50 (4.11) | 4876 (3.7) | 34.50 (5.0) | 12.72 (3.6) |
1.5:1 | 1200 | 34.00 (3.71) | 5029 (4.0) | 29.11 (4.8) | 10.02 (3.1) | |
2.0:1 | 1200 | 40.39 (2.9) | 7094 (3.5) | 26.42 (5.1) | 8.95 (3.1) | |
2.5:1 | 1200 | 46.00 (3.8) | 8303 (4.2) | 27.11 (3.6) | 7.64 (4.1) | |
3.0:1 | 1200 | 50.12 (3.5) | 9111 (2.9) | 25.50 (4.2) | 5.21 (2.6) | |
Control | 1:1 | 800 | 25.00 (4.0) | 4128 (2.8) | 36.11 (3.8) | 10.84 (4.1) |
1.5:1 | 800 | 27.64 (3.5) | 4324 (3.5) | 34.40 (4.1) | 7.64 (5.0) | |
2.0:1 | 800 | 31.00 (3.2) | 5754 (4.0) | 30.02 (4.8) | 5.44 (4.2) | |
2.5:1 | 800 | 36.03 (3.10) | 7182 (3.4) | 28.11 (3.7) | 4.50 (3.7) | |
3.0:1 | 800 | 41.15 (3.7) | 8389 (3.8) | 26.06 (2.6) | 3.90 (3.5) | |
Cold water | 1.0:1 | 1200 | 33.50 (5.0) | 6238 (4.1) | 30.44 (4.5) | 9.85 (4.6) |
1.5:1 | 1200 | 39.67 (4.4) | 7014 (3.9) | 27.51 (7.0) | 7.08 (4.8) | |
2.0:1 | 1200 | 47.61 (4.3) | 9800 (3.5) | 25.13 (3.1) | 6.11 (4.1) | |
2.5:1 | 1200 | 50.11 (2.7) | 12,180 (2.9) | 23.80 (4.4) | 4.02 (3.6) | |
3.0:1 | 1200 | 56.12 (4.8) | 13,300 (5.0) | 22.00 (2.9) | 4.81 (3.6) | |
Cold water | 1.0:1 | 800 | 30.11 (3.3) | 4899 (1.5) | 32.62 (3.1) | 9.11 (3.2) |
1.5:1 | 800 | 34.00 (3.1) | 5295 (2.8) | 28.96 (2.7) | 7.53 (2.9) | |
2.0:1 | 800 | 39.65 (5.0) | 6611 (2.1) | 26.41 (4.6) | 5.68 (2.7) | |
2.5:1 | 800 | 45.80 (3.6) | 7710 (3.0) | 23.01 (3.2) | 4.02 (4.1) | |
3.0:1 | 800 | 49.81 (4.3) | 9245 (3.2) | 20.85 (3.0) | 3.48 (3.7) | |
Hot water | 1.0:1 | 1200 | 31.76 (4.5) | 7746 (3.1) | 26.12 (2.5) | 9.00 (2.6) |
1.5:1 | 1200 | 40.01 (3.1) | 8821 (4.1) | 25.15 (1.8) | 8.141 (2.3) | |
2.0:1 | 1200 | 46.81 (2.8) | 11,294 (4.3) | 26.00 (2.1) | 6.01 (1.8) | |
2.5:1 | 1200 | 51.11 (4.1) | 13,203 (2.9) | 24.41 (3.0) | 4.64 (1.9) | |
3.0:1 | 1200 | 67.89 (6.1) | 14,736 (5.1) | 23.01 (1.9) | 4.01 (3.0) | |
1.0:1 | 800 | 30.06 (3.0) | 6416 (4.2) | 28.14 (2.4) | 7.15 (2.7) | |
1.5:1 | 800 | 38.02 (3.1) | 7917 (3.9) | 28.62 (2.3) | 6.02 (3.1) | |
2.0:1 | 800 | 44.81 (2.9) | 9721 (4.7) | 24.05 (2.5) | 5.00 (2.0) | |
2.5:1 | 800 | 47.00 (3.3) | 9800 (4.0) | 22.17 (1.8) | 4.12 (3.0) | |
3.0:1 | 800 | 56.11 (5.0) | 11,544 (3.2) | 20.02 (1.7) | 3.08 (1.0) | |
1% NaOH | 1.0:1 | 1200 | 45.12 (3.8) | 9846 (5.0) | 24.67 (2.6) | 7.00 (2.1) |
1.5:1 | 1200 | 50.83 (2.9) | 11,109 (3.0) | 23.02 (1.8) | 5.01 (1.2) | |
2.0:1 | 1200 | 57.10 (4.1) | 12,314 (3.8) | 21.14 (1.5) | 5.21 (1.2) | |
2.5:1 | 1200 | 64.25 (3.0) | 13,444 (4.4) | 16.65 (1.2) | 4.22 (1.0) | |
3.0:1 | 1200 | 73.45 (4.8) | 15,065 (4.1) | 15.01 (2.1) | 3.98 (0.9) | |
1.0:1 | 800 | 38.91 (3.1) | 7721 (4.9) | 26.88 (2.4) | 6.92 (2.1) | |
1.5:1 | 800 | 42.11 (2.9) | 9327 (4.4) | 24.11 (1.7) | 7.11 (1.6) | |
2.0:1 | 800 | 48.61 (3.9) | 10,870 (4.7) | 21.00 (1.2) | 5.04 (1.4) | |
2.5:1 | 800 | 53.55 (3.7) | 11,378 (3.8) | 18.42 (1.3) | 3.81 (1.7) | |
3.0:1 | 800 | 66.80 (4.0) | 13,154 (3.0) | 16.30 (1.1) | 3.04 (1.2) |
Reported values are the weighted average of four (4) tests per production mix. ( ) = Nos in parenthesis are the co-efficient of variations in %. All test specimens were conditioned at 20˚C ± 2˚C and 65% ± 1% relative humidity for 2 weeks before test.
. Summary of factorial analysis showing the effects of manufacturing mix on properties of Bambusa vulgaris—ce- ment composite panel
Source of variation | Degree of freedom | Mean square and F-values for panel properties | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Mechanical properties | 24 hrs horizontal water soak | |||||||||
Modulus of rupture | Modulus of elasticity | Water absorption | Thickness swelling | |||||||
MS × 104 | F | MS × 1010 | F | MS × 104 | F | MS × 104 | F | FTab | ||
Main effects | ||||||||||
Cement/B. vulgaris mix ratio | 4 | 0.152 | 2.92*K | 1.655 | 15.18** | 1.304 | 18.11** | 0.432 | 3.86** | 3.44 |
Soak treatment | 3 | 0.164 | 3.15*a | 1.499 | 13.29** | 1.109 | 15.40** | 0.310 | 2.77*a | 3.91 |
Density | 1 | 0.148 | 2.85NS | 2.617 | 24.01** | 0.405 | 5.63* | 1.023 | 9.13** | 6.84 |
First order interaction | ||||||||||
Mix ratio/density | 4 | 0.911 | 17.52** | 3.835 | 35.18** | 1.071 | 14.88** | 3.084 | 27.54** | 3.44 |
Mix ratio/soak treatment | 4 | 0.630 | 12.12** | 2.046 | 18.77** | 0.224 | 3.11*K | 1.816 | 16.21 | 3.44 |
Soak treatment/density | 3 | 0.512 | 9.85** | 1.325 | 12.16** | 0.188 | 2.61*a | 0.301 | 2.69*a | 3.91 |
Second order interaction | ||||||||||
Mix ratio/density/soak treatment | 4 | 0.448 | 8.62** | 4.472 | 41.03** | 0.897 | 12.46** | 0.416 | 3.71** | 3.44 |
Error | 136 | 0.052 | - | 0.109 | - | 0.072 | - | 15.232 | 0.112 | - |
Total | 159 | - | - | - | - | - | - | - | - | - |
NSNot significant at 0.05 level (FTab = 3.91). *Significant at 0.05 level. **Significant at 0.01 level. *kFTab = 2.43 at 5% level of significance. *FTab = 2.67 at 5% level of significance.
significant at 0.01% level of probability. This tends to suggest that MOE is a more sensitive measure of the importance of manufacturing variables on properties of wood/cement composites than MOR. It also goes to suggest that structural integrity as could be adjudged from compaction ratio and/or relative void volume play more significant roles in determining MOE of wood-cement composite panels. This later argument is in accord with the findings of Lingfei who corroborated properties with internal structures of bamboo/cement composite panels using X-ray diffraction (XRD), Thermo-gravimetric differential analysis (TG-DTA) and Scanning Election Microscopy (SEM) [
The cement/B. vulgaris composite panel’s WA properties after a 24 hrs horizontal water soak ranges from an average low of 15.01% to a max 36.11% (see
The percentage thickness swelling (% TS) due to a 24 hrs horizontal water soak is in
The studies have proved that B. vulgaris grown in Anambra river basin, southeast, Nigeria can be used to produce cement composite panels of acceptable properties as all panels produced met property requirements of ANSI-208-1 and ANSI-208-2; BS 5669 and MS 934 [
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*Corresponding author.