| 摘要 |
PROBLEM TO BE SOLVED: To provide a permeable block excellent in permeability and strength, having no worry about clogging even when it is used for a long period of time and reducing lowering of a permeable function and a manufacturing method. SOLUTION: A permeable block is so constituted that it has layer constitution consisting of a surface layer and a basic layer, both surface and basic layers contain inorganic aggregate grains and that coefficient of permeability is higher than 1×10-2 cm/sec, (1) percentage of void of the surface layer is within a range of 25-50%, average grain size of the aggregate grains is within a range of 0.5-2 mm and, at the same time, the maximum size and average grain size is smaller than the aggregate grain of the basic layer, (2) the percentage of void of the basic layer has 10% or more, at the same time, the percentage of void is lower than that of the surface layer, and the average grain size of the aggregate grains is within a range of 1.5-2.5 mm, and the above problems are solved by the permeable block and its manufacturing method.
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