A Comparative study on the strength of Japanese and Philippine bamboo reinforced concrete hollow block wall as a main component of a low cost two-storey building

This study primarily aimed to determine whether the construction method used in Japan for the bamboo-reinforced concrete hollow block wall would be applicable here in the Philippines with the local materials used. It is to evaluate the strength of the bamboo-reinforced CHB wall and to determine whether bamboo reinforcement could be a replacement for steel reinforcement for walls.
Specifically, this study is intended to answer the following questions:
1. What are the differences of the bamboo in the Philippines and Japan?
2. Is the construction method used in Japan for bamboo-reinforced concrete wall applicable in the Philippines with its local materials?
3. Can bamboo be used as reinforcement for CHB walls?
4. Will the addition of bamboo reinforcement increases the compressive strength of the Sample?
5. At what percentage of bamboo reinforcement will the compressive strength be the greatest?

This study was focused on the field test of bamboo-reinforced CHB wall test in St. Arnold Janssen Village, Soong, Lapu-Lapu City, Cebu on a sunny day last November 26, 2012 at around 1pm where 40 Civil Engineering Students from CIT-University participated. It was done using the same method of construction and testing as conducted in the joint research of Dr. N. Yashima in Japan where the same load cell and data indicator were brought from.
This study uses experimental research design consisting of a test in flexure of bamboo reinforced CHB wall. The test incorporates the tensile stresses determined in the related study conducted in Ichikawa High School (N. Yashima 2010). Wall testing includes bamboo preparation, reinforcement preparation, laying of CHB and the conduction of the tests to determine the strength of the bamboo reinforced concrete hollow block using measuring devices, turnbuckles and load measuring tool and measuring tape. The beam test setup and instrumentation are described in detail.

Specimen Selection and Preparation
In the selection of bamboo, only bamboo showing a pronounced brown color was used to ensure that the plant is at least three years old. The longest large diameter culms available were selected. Whole culms of green, unseasoned bamboo were not used. Bamboo cut in spring or early summer was avoided. These culms are generally weaker due to increased fiber moisture content.
Splints (split culms) are generally more desirable than whole culms as reinforcement. Larger culms should be split into splints approximately ¾ inch wide and length of approximately 1.49 meters of which 30mm is embedded in the footing. Splitting the bamboo can be done by separating the base with a sharp knife and then pulling a dulled blade through the culm. The dull blade will force the stem to split open; this is more desirable than cutting the bamboo since splitting will result in continuous fibers and a nearly straight section.
Bamboo nails were added to the bamboo splints since bamboo splint cannot provide great adhesion with mortar. The nails had a 6mm diameter and spaced at 40mm o.c. Bamboo reinforcement were spaced at 360mm.
Concrete Mix Proportions
The same mix designs were used as would normally be used with steel reinforced concrete. Concrete slump should be as low as workability will allow. Excess water causes swelling of the bamboo. High early-strength cement is preferred to minimize cracks caused by swelling of bamboo when seasoned bamboo cannot be waterproofed.
Construction of Model
The sample dimension of the wall was 1.090m x 0.745m since it was designed for a low cost housing which is semi-concrete using a hollow block with a dimension of 180mm x 350mm. The hollow blocks were placed in a straight manner ? one hollow block was positioned the same as the one below it.
Sample was tested 7 days after its construction. The testing involved setting up of a turn-buckle attached from a steel plate which was nailed to the wall. A measuring device which records the load applied and corresponding displacement shall be attached to the turn-buckle.
After the testing, the data result were gathered and graphed. It was then analysed to determine the strength of the wall. If it is necessary, a retest should be done to get an accurate result. The failure (a diagonal crackled in hollow blocks, wall uprooted from the footing, or failure of the reinforcement) of the wall was checked and design improvement was recommended.
Based on the data gathered from the experiments and researchers made on the related studies, the researchers concludes that
1. The difference of the bamboo specimens from japan and from the Philippines was their maximum tensile stress wherein Japanese bamboo had 213 MPa while Philippine bamboo?s tensile stress was 263 MPa. This clearly proved that Philippine bamboo is much stronger than Japanese bamboo.
2. Based on the limited number of testing conducted, it was concluded that the construction method used in Japan is not applicable here in the Philippines when using the latter?s local materials. The shear cracks on the CHB showed that the local Philippine CHB is way too weak compared to that of Japan since the bamboo reinforcements remained intact after the failure. The researchers further investigated the compressive strength of Philippine CHB and found that its strength was only 0.74 compared to that in Japan which was 10MPa.
3. Based on the results of the tests conducted, it is concluded that bamboo cannot be used as reinforcement for CHB walls since the Philippine CHB is weak since it is substandard.
4. Based on the limited number of testing conducted, it can be concluded that indeed addition of bamboo reinforcement would increase the compressive strength of the components of the wall.
5. Based on our findings, the compressive strength of the specimens increases as the bamboo reinforcement ratio increases. But, there should be a limit so as to the maximum viable bamboo ratio would not exceed 3%-5% based on the related studies.
After thorough analysis of the data and careful scrutiny of the details of the prototype wall, recommendations are hereby made:
1. Further investigate and improve the water ? cement ratio of CHB and concrete mixture for both the model and the actual structure and incorporate its properties to the study to attain optimum strength of shear wall and ensure a fully engineered house thus making the gathered data more accurate and reliable.
2. Another model should be provided for retesting after a length of time to determine the variation of data due to time factor, possible deterioration and inconsistencies of the experiment.
3. Make further experiments on this matter so as to prove that the bamboo reinforced CHB wall with the materials available in the Philippines be the resource used to build low cost houses.
4. A further study should be conducted to determine the equivalent steel reinforcement ratio of a particular bamboo reinforcement ratio.
5. An extensive study of evaluate the behavior of different types of bamboo is recommended as the bamboo type and behavior is different at different regions of the world.
6. A future study on the low frequency fully cyclic experimental tests could be conducted to identify the behavior of bamboo reinforced concrete in earthquake induced ground acceleration and distinguish whether it can withstand seismic load.

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