PROBLEM TO BE SOLVED: To obtain an asphalt structural material which is usefully applied to especially a rail road ballast to effectively prevent its subsidence by mixing heated asphalt under agitation with a small-diameter member made of an ore, glass, a fiber such as of a synthetic resin or/and a visoelastic material.
SOLUTION: Asphalt heated to a viscosity at which it is mixable is mixed under agitation with a small-diameter member having specified strength, specified heat resistance and specified dispersibility to form a mixture. This mixture is made more flowable by heating and poured into a railroad ballast on which an aggregate is laid to fill the gaps of aggregate components and cured. The small-diameter used is a fibrous or particulate one made of a metal, a ceramics, an ore, carbon, glass, a synthetic fiber or an animal or vegetable material. This material may further contain a suitable combination of a flow improver with a viscoelasticity improver.