Laboratory experiments were conducted to study the effect of percolation rate on methane emission from paddy soil during continuous flooding, in order to examine the practical possibility of methane emission control by water management at paddy field sites. Typical formations of paddy field soil layers were reproduced in cylindrical columns without rice plants for measurement of methane emission under various percolation rates. Two experiments were conducted. In Run 1, the percolation rate was fixed at around 10 mm d-1 and 20 mm d-1 to understand the tendencies of methane emission under high and low percolation conditions. In Run 2, the percolation rate was changed stepwise in the range between 5 mm d-1 and 30 mm d-1 to analyze the quantitative relationship between percolation rate and methane emission. It was revealed that the relationship between percolation rate and methane emission is linear with a negative slope. Notably, the slope of the line describing the relationship is affected by the percolation history of the soil. Once the percolation rate reached around 30 mm d-1, which is a very high percolation rate in practical paddy fields, methane emission did not return to the initial value if the percolation rate was decreased. These results suggest that reduced methane emission would be made possible by increasing the percolation rate of practical paddy fields.
High-quality aggregate has become increasingly difficult to obtain in Japan. One solution to this problem of dwindling aggregate resources is the effective use of both industrial by-products and low-quality aggregate. In this study, characteristics of drying shrinkage in mortar using various industrial by-products and low-quality aggregate were examined. Crushed sand, recycled sand, granite muck, waste tire, waste glass and two types of fly ash (Type I and Type IV) were used in place of standard sand or cement. As a result, there is a possibility that granite muck had highly utility as fine aggregate because it does not exacerbate drying shrinkage. Waste glass can be used as fine aggregate from the viewpoint of drying shrinkage when the replacement ratio against volume of standard sand is 10% and 30%. The amount of strain in mortar using non-water-absorbing material strongly correlates with mass decrement.