1:45 PM - 3:15 PM
[O11-P84] Clay mineralogical Analysis using Instrumental Analysis -Successful soil for “Sagano Yaki” –
Keywords:Forested soil, Clay minerals, X-ray diffraction analysis, Autograph, Erosion
1. Introduction
Clay for pottery is often sourced locally. However, Kyo-yaki potters often say that “there is no clay in Kyoto” (Taniguchi, 2015). Currently, there are no places in Kyoto where clay can be extracted in quantities sufficient to meet industrial demand.
The Sagano High School Woods for Field Studies (hereafter referred to as “SWFS”) contains reddish clay-rich soil, to the extent that locals refer to it as “Red Clay Mountain.” In the past, clay was extracted from this area. However, potters have evaluated this soil as “difficult to use on its own” (Taniguchi et al., 2024).
Various methods are used to identify clay minerals, such as X-ray diffraction, differential thermal analysis, and infrared absorption spectroscopy. Okubo (2017) reported XRD analysis results on the clay fraction of soil from SWFS.
Additionally, Sayama (2020) reported that commercially available paving stones are effective for maintaining trails in SWFS but raised concerns about the environmental impact of bringing in such materials.
Therefore, in aiming to realize the production of “Sagano-yaki,” the first objective of this study was to clarify the physicochemical properties of the soil using thermal analysis and an accurate universal testing machine. The second objective was to examine the use of paving stones as a sustainable way to utilize soil from the school forest.
2. Method
The thermal properties of the school forest soil, red soil, and white soil were evaluated using thermogravimetric-differential thermal analysis (Shimadzu Corporation, DTG-60AH). Platinum was used as the reference material. Measurements were conducted in air and nitrogen atmospheres, with the temperature raised from room temperature to 1200°C at a rate of 20°C per minute.
Star-shaped and regular tetrahedron shapes were selected for the paving stones, as these forms are more stable on slopes. The formed school forest soil and red soil were heat-treated at drying, 105, 350, 550, 750, 950, and 1150°C using a bench muffle furnace (Daiken Corporation).
Compressive strength tests were performed using a universal testing machine, Autograph AGX-V2 (Shimadzu Corporation), to verify whether the strength was sufficient for use as paving stones. Additionally, erosion prevention tests were conducted in SWFS to assess the effectiveness of the produced paving stones.
3. Results and Discussion
X-ray diffraction of the clay fraction of the school forest soil revealed that it contains 2:1 type layer silicate minerals such as vermiculite and illite; the 1:1 type layer silicate mineral kaolinite; the iron hydroxide mineral lepidocrocite; and quartz (Okubo, 2017).
Thermal analysis of the school forest soil showed peaks around 90–100°C, 270°C, 500°C, 580°C, and 910°C. Generally, dehydroxylation of OH groups in 1:1 type minerals occurs at lower temperatures than that in 2:1 type layers (Hakusui, 1988). Because the dehydration peaks started at relatively low temperatures, it is inferred that the proportion of 1:1 type minerals is high.
Based on the mineral species reported by Okubo (2017) and the DTA data in this study, the gentle kaolinite peak starting in the low-temperature range suggests that the clay minerals have low crystallinity and that other minerals may also be present.
The strength of the handmade paving stones increased with higher firing temperatures. Compressive strength testing showed that they had sufficient strength to be used as paving stones.
Furthermore, erosion prevention tests showed no significant difference in runoff between the star-shaped and tetrahedral paving stones, suggesting that both are effective for erosion control.
4. Conclusion
This study provided a detailed clay mineralogical analysis of the soil from the school forest. In the future, it will be desirable to conduct further experiments using infrared absorption spectroscopy and selective dissolution treatments.
In addition, this research has revealed the potential to use Sagano-yaki as paving stones. To promote environmentally friendly usage, all production processes should ideally be carried out within the school forest.
Since previous fire tests conducted in the school forest confirmed that the core temperature reached 550°C, a firing test within the school forest is planned.
Clay for pottery is often sourced locally. However, Kyo-yaki potters often say that “there is no clay in Kyoto” (Taniguchi, 2015). Currently, there are no places in Kyoto where clay can be extracted in quantities sufficient to meet industrial demand.
The Sagano High School Woods for Field Studies (hereafter referred to as “SWFS”) contains reddish clay-rich soil, to the extent that locals refer to it as “Red Clay Mountain.” In the past, clay was extracted from this area. However, potters have evaluated this soil as “difficult to use on its own” (Taniguchi et al., 2024).
Various methods are used to identify clay minerals, such as X-ray diffraction, differential thermal analysis, and infrared absorption spectroscopy. Okubo (2017) reported XRD analysis results on the clay fraction of soil from SWFS.
Additionally, Sayama (2020) reported that commercially available paving stones are effective for maintaining trails in SWFS but raised concerns about the environmental impact of bringing in such materials.
Therefore, in aiming to realize the production of “Sagano-yaki,” the first objective of this study was to clarify the physicochemical properties of the soil using thermal analysis and an accurate universal testing machine. The second objective was to examine the use of paving stones as a sustainable way to utilize soil from the school forest.
2. Method
The thermal properties of the school forest soil, red soil, and white soil were evaluated using thermogravimetric-differential thermal analysis (Shimadzu Corporation, DTG-60AH). Platinum was used as the reference material. Measurements were conducted in air and nitrogen atmospheres, with the temperature raised from room temperature to 1200°C at a rate of 20°C per minute.
Star-shaped and regular tetrahedron shapes were selected for the paving stones, as these forms are more stable on slopes. The formed school forest soil and red soil were heat-treated at drying, 105, 350, 550, 750, 950, and 1150°C using a bench muffle furnace (Daiken Corporation).
Compressive strength tests were performed using a universal testing machine, Autograph AGX-V2 (Shimadzu Corporation), to verify whether the strength was sufficient for use as paving stones. Additionally, erosion prevention tests were conducted in SWFS to assess the effectiveness of the produced paving stones.
3. Results and Discussion
X-ray diffraction of the clay fraction of the school forest soil revealed that it contains 2:1 type layer silicate minerals such as vermiculite and illite; the 1:1 type layer silicate mineral kaolinite; the iron hydroxide mineral lepidocrocite; and quartz (Okubo, 2017).
Thermal analysis of the school forest soil showed peaks around 90–100°C, 270°C, 500°C, 580°C, and 910°C. Generally, dehydroxylation of OH groups in 1:1 type minerals occurs at lower temperatures than that in 2:1 type layers (Hakusui, 1988). Because the dehydration peaks started at relatively low temperatures, it is inferred that the proportion of 1:1 type minerals is high.
Based on the mineral species reported by Okubo (2017) and the DTA data in this study, the gentle kaolinite peak starting in the low-temperature range suggests that the clay minerals have low crystallinity and that other minerals may also be present.
The strength of the handmade paving stones increased with higher firing temperatures. Compressive strength testing showed that they had sufficient strength to be used as paving stones.
Furthermore, erosion prevention tests showed no significant difference in runoff between the star-shaped and tetrahedral paving stones, suggesting that both are effective for erosion control.
4. Conclusion
This study provided a detailed clay mineralogical analysis of the soil from the school forest. In the future, it will be desirable to conduct further experiments using infrared absorption spectroscopy and selective dissolution treatments.
In addition, this research has revealed the potential to use Sagano-yaki as paving stones. To promote environmentally friendly usage, all production processes should ideally be carried out within the school forest.
Since previous fire tests conducted in the school forest confirmed that the core temperature reached 550°C, a firing test within the school forest is planned.