Pouring Concrete with a Pressure Chamber

WHEN pouring concrete it frequently happens that space prohibits the placing of a mixer at the point, or points, where the concrete is to be used. Usually in such cases recourse is had to some form of pressure chamber, or concrete gun, to blow the mix by compressed air from the mixer to the point of pouring. Recently such a case arose at one of the western mines. The experience obtained there may be of benefit to others, not expert in the means of transporting mixed concrete, when they run up against similar situations. The first stage in pouring in this instance was a vertical drop of 100 ft. from the mixer on one level to the point where horizontal travel began on a lower level. Standard 6-in. pipe with flange joints was used, hung in the shaft space available. A standard 45" bend near the bottom directed the mix, with free discharge, into an air chamber for the horizontal stage of travel. With an air chamber at the mixer and pressure applied to the falling mix in the vertical section, jamming frequently occurred at the turn and the pipe would have to be taken apart for freeing. To obviate this difficulty the mix was poured slowly without the addition of air pressure, when it was found that the mix got through much better.