| dc.description.abstract | Volcanic ash is high in mordenite, an mineral ingredient characterized by having a large specific area and being able to retain considerable quantities of moisture. On the other hand, Kanuma soil, the weathered volcanic ash, which is rich in allophane, also showing high performance with respect to moisture retention. These natural porous materials offer an opportunity to prepare a passive humidity-controlling material. This study investigated the feasibility of generating functional ceramics with controlled pore size and pore volume in an appropriate humid range of living environment, by sintering mixture of volcanic ash, Kanuma soil, and glass. The sintering conditions, including sintering time (holding time 5-10min), sintering temperature (ranging from 800-830oC), and mix design with various portion of glass amendment were tested. The resultant humidity-controlling ceramics samples were analyzed for their pore distribution and pore volume, adsorption and desorption characteristics, and engineering properties (ie., bending strength, water adsorption, bulk , density, and shrinkage).
The results indicate that for all tested conditions, the bending strength of all resultant volcanic ceramics samples were higher than 7MPa. And all Kanuma ceramics samples except those generated at 800oC 5min, with 65%(w/w) glass amendment, and 800oC 10min, with 60%(w/w) glass amendment, were all greater than 6MPa. The bending strength in both cases were all satisfying with the fractural intensity specification of ceramics (minimum 6MPa). The results of pore size distribution analysis indicate that volcanic ceramics samples tended to distribute in the range from 70-100nm(dia), whereas Kanuma ceramics samples in the range of 3-12nm(dia), the distribution suggesting that Kanuma ceramics samples are effective in moisture adsorption at lower relative humidity, and the volcanic ceramics samples on the contrary. The adsorption and desorption as tested by the Japanese test method for humidity-controlling building material shows that some volcanic ceramics samples fell in Level one moisture-controlling material (29 kg/m2x10-3), whereas some Kanuma ceramics samples reaching Level three (71 kg/m2x10-3).
In conclusion, this study demonstrated that humidity-controlling materials can be generated by sintering volcanic ash and/ Kanuma soil with glass amendment, taking advantage of the inherent porosity of the natural materials. Especially, ceramics samples prepared from Kanuma soil show excellent performance as a humidity controlling building material.
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