PURPOSE: To prevent remaining of powdered particles on a supporting beam and formation of cracks of a filling material by filling the part positioned on the supporting beam of a grating with the hardened filling material which has the composition of the liquid material containing latex, cement, and aggregates.

CONSTITUTION: A plurality of supporting beams 6 and a grating 7 having spaces 11 for allowing powdered particles to pass between a number of lattices 8 bridged onto the supporting beams 6 are arranged as a deck for selectively accommodating cars and powdered particles. The part positioned on the supporting beams 6 in the space 11 of the grating 7 is filled with hardened filling material 12. As said filling material, the material having the composition of the liquid material containing rubber and latex in 3W15%, cement, and aggregates is used. Therefore, remaining of powdered particles on the supporting beams 6 is prevented, and the formation of cavity and crack due to the contraction of filling material, and compression, impact, etc. due to the passing of cars is prevented.