Abstract: A soil or ground reinforcing material consisting of Al--Fe oxides mixture the main contents of which are iron oxide made from fine iron oxide powder byproduced in steel production and Aluminum oxide made from red mud by-produced in Aluminum smeltering and lime added therein is mixed into a soil containing crushed stones, natural soil, etc., and further Titanium oxide is mixed into the above soil or ground reinforcing material to make Al--Fe--Ti oxides mixture in which lime is added and mix this material into a soil or ground containing crushed stones, natural soil, etc. to enhance the strength and viscoelasticity thereof. The content of the Titanium oxide in the soil or ground reinforcing material is within the range of 0.5-2.0% by weight.