| Summary: | 碩士 === 國立成功大學 === 土木工程學系碩博士班 === 96 === Different fractions of reservoir sludge and rice hull were first mixed and then sintered at high temperatures to produce spherical media with various size and water holding capacity. The physical properties of the spherical media, including air-filled porosity, container capacity, bulk density, particle crushing strength, pH value and electrical conductivity, were measured and compared to each other to suggest some candidate spherical media for plants. At the same time, the effects of rice hull length, sphere size and rice hull content on the physical properties of spherical media are evaluated and compared to those of commercially available LECA and perlite.
The required physical properties of candidate spherical media for plants are: air-filled porosity 5-50%, container capacity 20-60%, particle crushing strength 0.5MPa and bulk density 0.3-0.75g/cm3. The physical properties of the spherical media with single size manufactured here are measured experimentally: air-filled porosity 40-43%, container capacity 13-39%, bulk density 0.409-1.096g/cm3, particle crushing strength 1.55-68.9kgf/cm2. Also, air-filled porosity 33-43%, maximum container capacity 44% are found for the spherical media with dual size. Five of the 21 different spherical media produced in the study satisfy the required physical properties of candidate spherical media for plants. Especially, the particle crushing strength of the spherical medium with the highest container capacity, 4 times of LECA, is still higher than that of LECA and perlite.
The heights of Bermuda grasses planted on the spherical medium produced here, soil and LECA are approximately the same after 12 weeks. In addition, it is found that the height and coverage rate of Taipei grasses planted on a spherical medium with a higher container capacity is superior to those with a lower container capacity.
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