PURPOSE: To improve the adhesivity of a specific organic polymer cloth by treating with actinic energy ray and/or an organic silane compound.
CONSTITUTION: A flat yarn cloth of an organic polymer such as polyolefin, polyester, polycarbonate or polystyrene or a cloth produced by alternately crossing slit yarns of a film at proper spacings and thermally welding the crossing points is used in the present process. The adhesivity of the cloth is improved by subjecting the cloth to e.g. irradiation with actinic energy ray (e.g. corona discharge treatment), coating with an octane solution of an organic silane compound such as allylethoxysilane followed by drying, treatment with organic silane compound after corona discharge treatment or irradiation with electron ray after organic silane treatment. The treated cloth is coated with a hydraulic inorganic paste produced by mixing cement, silica sand, gypsum, light-weight aggregate, thickener, etc., at specific ratios, wound around a core facing the paste inward and cured to obtain the objective hydraulic inorganic material.