| 摘要 |
PURPOSE: A soil composition for a playground emits far-infrared radiation using biotite to be good for health and is excellent at draining without a large amount dust scattering. CONSTITUTION: A soil composition for a playground contains 15-25 volume% of biotite, 20-30 volume% of red clay, and 50-60 volume% of granite soil. The biotite contains 10-20 volume% of grains with particle size less than 0.3mm, 50-70 volume% of grains with particle size between 0.3 mm and 1 mm, and 20-30 volume% of grains with particle size between 1 mm and 3 mm. |
