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Research Article
 

Strength Properties of Preservative Treated Gigantochloa scortechinii after Vacuum Impregnation Process



Razak Wahab, Janshah Moktar , Mahmud Sudin and Hashim W. Samsi
 
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ABSTRACT

Strength properties of preservative treated two-year-old and four-year-old Gigantochloa scortechinii Gamble were evaluated. The preservatives used in the study were Ammonium Copper-Quaternary (ACQ), Copper Chrome Arsenic (CCA) and Borax Boric Acid (BBA) at 2 and 4% concentrations using vacuum pressure impregnation process. It was found that there was an overall strength reduction in the treated bamboo immediately after treatment. The strength reduction ranged from 4.9 to 7.6% for ACQ, 5.0 to 7.2% for BBA and 5.9 to 7.9% for CCA treated bamboo. The reduction in strength was found to be dependent on the type of preservatives applied, concentration used and their retention in the bamboo.

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  How to cite this article:

Razak Wahab, Janshah Moktar , Mahmud Sudin and Hashim W. Samsi , 2006. Strength Properties of Preservative Treated Gigantochloa scortechinii after Vacuum Impregnation Process. International Journal of Agricultural Research, 1: 8-13.

DOI: 10.3923/ijar.2006.8.13

URL: https://scialert.net/abstract/?doi=ijar.2006.8.13

Introduction

The strength properties of bamboo have been investigated by a number of researchers. It possesses excellent strength properties that are as good as other building materials like steel, concrete and timber (Janssen, 1985). The strength of bamboos are associated with their anatomical structure and composition particularly the fibres and parenchyma. It relies to a large extend on the quantity and quality of fibres. However, the strength of bamboo varies with respect to species, age, moisture content and position along the culm (Limaye, 1952; Lavers, 1969; Janssen, 1981; Liese, 1987).

An optimum strength occurs when bamboo attained its maturity age of around 3-4 years. For this reason bamboo are harvested at this age especially for structural or other heavy-duty uses (Liese, 1986; Sattar et al., 1990; Kabir et al., 1993; Espiloy, 1994).

Compressive strength was found to increase with height while the bending strength showed a decrease in bending strength (Kabir et al., 1991, 1993; Sattar et al., 1990; Liese, 1986; Abd. Latif, 1991; Espiloy, 1985; Janssen, 1985; Limaye, 1952). The compressive and the bending strength also increased from the inner part to the periphery of the culm wall.

Treating bamboo with preservative is intended to increase the life span service of the bamboo and their products. However, questions arise on whether the treatments process will affect the strength properties of the bamboo. Although several studies on strength properties have been conducted, information on the bamboo strength properties after treatment is not available somehow.

The aim of this study was to investigate the effect of treatment using various preservative on strength properties of bamboo with emphasis on the strength reduction. The strength reduction being investigated is static bending (MOR) and compression parallel to the grain.

Materials and Methods

All bamboo culm (G. scortechinii) used in this study were taken from Nami Forest Reserve area in Kedah, Malaysia from Jan. 2004 to July 2005. Each culm was equally crosscut into three length portion. Each sample has a length of 80 cm and with diameter ranging between 8 to 12 cm. Treatment were done on round bamboo with combination of Borax and Boric Acid (BBA) at ratio 1.54 : 1, Copper Chrome Arsenate (CCA) and Ammoniacal Copper-Quaternary (ACQ) at 2% and 4% by vacuum impregnation processes. Culm samples were placed in the treatment cylinder and treated under vacuum pressure condition. The treatment cycle protocol adopted was as follows: -

Initial vacuum - 600 mm Hg for 30 min (to take the air out of bamboo)
Applying Pressure - 12 kg cm-2 for 2 hr
Final vacuum - 600 mm Hg for 30 min (to remove the excess preservative from the bamboo)

After treatments all samples were sliced into strips of 2 cm x thickness x 80 cm length. Strength properties evaluated were static bending and compression parallel to grain and carried out in accordance to the ISO 22157 with some modification using the Shimadzu Computer Controlled Universal Testing Machine (ISO, 2004). All testing blocks were conditioned to 12% moisture content prior to testing. This was done by placing the test blocks in a conditioning chamber and controlled relative humidity, temperature and air-circulation for a week until the required equilibrium moisture contents were obtained. All testing on the mechanical properties of the bamboo were conducted at the UMS laboratory.

Results and Discussion

In general the strength properties conducted on the untreated 2 and 4 year old G. scortechinii varied with age and culm heights. Four-year-old bamboo possess better strength with an average increased about 4.2% for MOR and 10.3% for compression strength, as compared to two-year-old bamboo (Table 1). The increase may be associated with the basic densities, which were found to increase from 2 to 4 year-old culms and from the bottom to the top portion of the culms (Razak, 1998; Sulaiman, 1993). The age is considered to be an important factor influencing the strength properties of bamboo. These results are in agreement with the finding of Limaye (1952), Janssen (1981) and Abd. Latif (1991).

Table 1: Means strength properties of untreated 2 and 4 year-old G. scortechinii
* based on 2 year-old value;

Table 2: Preservative retention (km/m-3) of 2 and 4 year-old G. scortechinii bamboo treated by vacuum pressure impregnation process.

Table 3: Bending strength (MOR) and strength decreased of treated samples after vacuum pressure treatment (kg cm-2)
* Calculated based on 2 year-old value of untreated G. scortechinii culms
** Calculated based on 4 year-old values of untreated G. scortechinii culms

Table 4: Compression strength and decreased of treated samples after vacuum pressure treatment (kg cm-2).
* Calculated based on 2 year-old value of untreated G. scortechinii culms
** Calculated based on 4 year-old values of untreated G. scortechinii culms

Table 5: Summary Analysis of Variance for bending and compression strength for preservative treated blocks
* : Significant at p<0.01

The preservative retentions of the 2 and 4 year-old treated G. scortechinii are tabulated in Table 2 and the results of the strength tests are presented Table 3 and 4. The analysis of variances for both tests is shown in Table 5. There is a significantly higher amount of preservative retention on 2 year-old G. scortechinii compared to 4 year-old.

The presence of preservatives in G. scortechinii after the treatment process slightly decreased the strength properties of the bamboo. It was observed that there is a variation in the decrease of the strength properties that are dependent on the type of preservative and the age of the bamboo used. The overall results indicate a strength reduction of 4.9 to 7.6% for the ACQ, 5.0 to 7.2 for the BBA and 5.9 to 7.9% for the CCA. Bamboo samples treated with ACQ and CCA were found to reduce the bamboo strength properties slightly more than BBA. The 2 year-old culms show slightly higher reduction in strength properties than the 4 year-old culms.

Certain preservative are known to fix in the cell walls of the bamboo during the treatment process. This is especially true for CCA and ACQ. The fixing of this chemical might interfere with the chemical structure of the cell wall. As the results of this, some cellulose chain are broken down that might reduce the strength. BBA on the other hand is known to have no fixing ability and thus the effect on the treatment is reduce significantly compare to CCA and ACQ.

Conclusions

The MOR of the bending strength decreased from bottom to top portion of the bamboo culms. The 4 years bamboo has higher values between 3.7 to 4.5% then those of the 2 years old culms.
The compression strength increased from bottom to the top portion of the bamboo culms. The strength values of the 4 years bamboo have higher values between 7.3 to 13.2% compared to the 2 years bamboo culms.
Treating G. scortechinii culms with preservatives (ACQ, BBA and CCA) resulted in a slight decreased in the bamboo strength properties.
The rate of the strength decrease depend on the type of preservatives, the age of the culms used and chemical retention during treatment process in the bamboo culms.

Acknowledgment

The author would like to acknowledge Malaysian Forest Department for the support in supplying of the tested bamboo samples.

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