| 摘要 |
A method for dry spraying alpha or beta calcium sulfate hemi-hydrate (CaSO4.1/2H2O) which comprises blowing a stream of dry calcium sulfate hemi-hydrate particles through a hose to a spray nozzle, and prior to discharging the particles from the nozzle onto the surface to be sealed, introducing water into the stream of dry particles and intermixing the calcium sulfate hemi-hydrate particles and the water in the nozzle mixing chamber. In order to reduce dusting, it may be desirable to add additional water at the nozzle orifice. The amount of water added to the dry calcium sulfate hemihydrate particles is an important factor in achieving a satisfactory composition for adhering to and sealing the surface, and generally the method is practiced by using from about 200 to about 100 parts by weight of water per 100 parts by weight of calcium sulfate hemi-hydrate. The calcium sulfate hemi-hydrate/water admixture sets very rapidly whereby it can be applied in relatively thin coatings and still provide adequate sealing and strength properties. In some applications, it may be advantageous to incorporate cut glass fibers into the calcium sulfate hemi-hydrate which is preferrably accomplished by introducing the cut glass fibers into the wetted hemi-hydrate particles after they are discharged from the end of the nozzle. The method of this invention is particularly useful in sealing roof and wall surface in underground mines and may also be used to form structural members in the mines. |
