To provide a volcanic rock formed by kneading and solidifying volcanic ash together with cement or a hardening agent； and to provide a technology of a novel weed-proof execution method excellent in draining and a weed-proof effect by volcanic ash rocks having various sizes, concerning a weed-proof execution method related thereto.SOLUTION: A volcanic ash rock K formed by kneading and solidifying volcanic ash 1 together with cement 2 or a hardening agent 2A is pulverized into a range of 0.1 Cm to about 10 Cm, in terms of the outer diameter of the volcanic ash rock, and then mixed, and thereafter laid on a place where prevention of growth of weeds is required, such as a flower garden P1, a median strip P2 of an expressway or a green belt P3 in a park.SELECTED DRAWING: Figure 1【課題】火山灰にセメントや硬貨剤を混練して固化させた火山石と、これによる防草施工法に係わり、大小様々な火山灰石により水はけと防草効果に優れた新規な防草施工法の技術に関する。【解決手段】火山灰１にセメント２や硬貨剤２Ａを混練して固化させた火山灰石Ｋは、上記火山灰石の外径を約０．１Ｃｍ～約１０Ｃｍの範囲に粉砕・混在した状態とし、花壇Ｐ１や高速道路の中央分離帯Ｐ２や公園の緑地帯Ｐ３における雑草の生育を防止したい箇所に敷設する。【選択図】図１
