The researchers looked into the characteristics of coal ashes from burning different types of coal in Japan to find ways to use them effectively. Japan uses various coal types, which means the properties of the resulting coal ash change based on the season and where it's used. So, understanding these differences is crucial for making the best use of coal ash. The study focused on the chemical, physical, soil, and leaching properties of coal ashes to see how they could be used in civil engineering projects in a large scale.