2023年度の短期研修では、アジスアベバ科学技術大学のFitsum Tesfaye Berhe先生、Eleyas Assefa先生が、京都大学工学研究科の安原先生、澤村先生とMNGDプロジェクト題目１，２の活動について話し合いました。司会は重田先生（京都大学）です。今回は全二回中の第一回です。
Discussion regarding Component 1 & 2 (Part1)
YASUHARA × SAWAMURA × FITSUM × ELEYAS [Moderator: SHIGETA]
Using plant additives without sieving and with cement or lime
SAWAMURA：Firstly, let me share my understanding of the Component 1, especially the progress and the future work. We started the research with the celldrone from 2016. When we add the celldrone to the muddy soils, the workability is improved, and the shear strength is also increased. If we add the plant additives, the soil property is also improved as same as FSP. When we conducted the experiment, we sieved the plant additives. I think this is very important and it is necessary for the laboratory testing. But it is very difficult when we consider the actual use of this technique. My suggestion is that we can consider using plant additives such as ensete, sugarcane bagasse, etc. without sieving it as it is. We have to evaluate the change of property of soil when we add these materials without sieving. I think this is the next step, but when we evaluate the property of these plants, we must change the method of test because the sample size must be larger. As the standard UCS sample is too small, we have to develop a new method which can evaluate the change of soil property.
And the second point to note is on the use of lime or cement. So far, we conducted many experiments by just adding the plant additives to the muddy soil. But in Japan, we already conduct some experiments using the combination of FSP and cement or lime or other materials. An interesting thing is that, for the celldrone and cement treated soil, the uniaxial compression strength of the soil is increased, and the toughness of the soil is also improved. I think the combinational use of the celldrone and the cement has a potential, and we have to continue studying these materials. So, in the future, we have to research on two things. One is on the larger size of the plant additives. The other is a combination of FSP and another material, lime or cement.
YASUHARA：Thank you. Shall we move on to the Component 2? I’d like to share some results regarding Component 2 briefly. I summarized what we have done so far, and then I will show you what we should do for the rest of our research period. The title of the Component 2 is “Development of production technology of cellulose-based soil modifiers using native plants”. We have three items to be conducted. One is to select the useful native plant resources and the second is to analyze the composition of the selected resources and determine the resources to be processed into the soil modifier. And the third is to develop the method for processing the native plant resources in the soil modifier. Dr. Sawamura has just told us we may use the plant additives without sieving. That may be the next step, but to do so, we must make manuals how to make the additives from the native plants.
First, we have selected the 12 candidate plants in the South Omo zone and Addis Ababa. Then, among them, we have selected the three important plants, ensete, coffee parchment, and sugarcane bagasse. Focusing on these three materials, we have to make a manual how to make the additives. As Dr. Sawamura has mentioned, we have to decide if we use only the plant additives or we should add some cementitious materials, like lime or cement to improve the black cotton soil.
We also have to make the manual for the usage of grain crusher. Checking the material morphology like the shape or the particle size, to be evaluated by changing the crushing condition, we must make the manual instructing how to prepare the additives.
The second task is that we conduct the water absorption tests to know the performance of the additives we selected and the chemical analysis to know the content of the cellulose, hemicellulose, lignin or ash, the chemical composition within the plant additives.
The selected additives (ensete, coffee parchment, the sugarcane bagasse) and/or cement or lime will be mixed with the black cotton soil in Ethiopia. Then we will do more mechanical tests to know the effect of the additives and cement, which are conducted together with the members of the Component 1. That’s what we’re thinking. Based on the previous results, we must know what kind of powder characteristics such as the shape and the grain size of the additives show good results. We should work together with ERA and discuss our future work. Dr. Fitsum, do you have any comments on the activities of Component 1 or Component 2?
FITSUM：Thank you very much. Well coincidentally, I was thinking about the points you raised last time when you were in Addis Ababa with Prof. Kamei. We looked at the raw material prepared in our laboratory, and we were discussing about the possibility of using the larger size plant materials. We have this practice in Ethiopia for thousands of years. For building houses, we use clay soils with chid, which is random size wheat straw. It increases the strength of the soil. My parents’ house is still standing for 60 years without any cracks. You need 15 to 20 days to ferment with chit, with the wheat straw. When you go to the southern part of Ethiopia, you can use it within a day mixing. I think there is some kind of chemical process going on over there. I supported this idea using bigger size of plant material from the beginning. How big? We need to know that. We need to define the size. But since we have started the experiment with 20/50 micrometers of the soil, we need to complete that to move on or we need to do it parallelly. I believe we need to complete the experimental as scheduled.
In Ethiopia, culturally, we tend not to document what we do; we keep it in our minds. Standardization and documentation, particularly the practical application, are areas we struggle with. For instance, ERA has a low-volume manual that is annexed to their main manual, but we rarely use it. Despite its availability, this resource often goes unutilized, highlighting our challenges in integrating formal documentation into our routine practices.
YASUHARA：I have the comment on your ideas. Actually, to make for the documentation we have to have two kinds of the documents. One is how to prepare the additive because we don’t fix how to make the additive. And then, we need that kind of documentation manual. The other manual is how to construct the low volume road. That’s another documentation. Definitely, at least we will need two kinds of manuals.
（Part 2へ続く）
