In order to reduce the environmental pollutions and develop a new type construction material with super lightweight and high strength, we did some fundamental studies on the mechanical behaviors. The three kinds of experimental samples were made of fly-ash and full hard polyurethane, whose special mix-ratio and producing methods are described in this investigation. The static mechanical characteristics were discovered in the three kinds of material tests, namely the compression test, the bend test, and the cleavage test. The mechanical behaviors of this new material are also compared with that of concrete in the investigation. The main results obtained in the study are : 1) the new material can be made of fly-ash and full hard urethane, 2) stress-strain relations are discovered in the tests, and 3) the new material can be used not only as reinforcement of steel structural system for seismic design, but also as expansion device for high-way bridge, due to its large capacities of transformation, remarkable lightweight and high strength.