PURPOSE: To raise the strength of concrete with better workability by a method in which fibers and cement-based hardening material are mixed, charged or spread in the ground, watered, and compacted.

CONSTITUTION: Steel or synthetic resin fibers of a fiber length of 30W50mm are mixed with a cement-based hardening material and fine aggregate without use of water. The mixture 2 is packed or spread in the ground, watered, and compacted by rolling, vibration, or impact to form a hardened fiber concrete. In the case of improvement in banking around, the mixture 2 and banking material 3 are alternately laid in a laminar form and then watered for accelerating hardening, where they are compacted by rolling, vibration, or impaction. The density and strength of the concrete can thus be enhanced.