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2015FallShotcreteEMag

Fig. 9: From the original design, this rig is the original predampener and mixing rig for the N-gun and has a 50-year field experience based off the original Micon rig design. This rig can mix moist sand and cement or predampen Fig. 7: N-gun or pressure vessel has 105 years prebagged material of field use. It is based off the original gun design from 1907-1910 and is called the double tank or chamber. This gun allows the material to continuously flow because the bottom chamber stays fully pressurized while the top chamber is being filled. With very few wear parts, these guns are built to last forever. The pressure is still used for pushing material 500 ft (150 m) vertically and 1000 ft (300 m) horizontally Fig. 10: From the original design this rig is a shorter version of the original predampener and mixing rig with a rotary barrel-type gun and hydraulic water booster pump designed to fit into low spaces, such as parking garages. This rig can mix moist sand and cement or predampen prebagged material Fig. 8: This auger-feed predampener and rotary moisture) and cement together, it would start the barrel gun combination is used in civil tunnels hydration process, making it easier for the noz- and mining projects. This is an electric feed zleman to regulate the water at the nozzle and machine for consistent material flow, along reducing the potential for building up static elec- with a peristaltic accelerator dosing pump that tricity from material moving through the hose. By injects the metered liquid into the water line to using completely dry material with no moisture, the nozzle for early set times of the in-place dry the hydration process did not start until the dry shotcrete material material reached the nozzle water ring. This author learned the hard way—getting hit by static elec- most specifiers started writing prepackaged com- tricity. I wrapped the nozzle hose with an inner pletely dry bagged materials in their repair tube; grounded the gun, couplings, and the hose specifications. This alone has deviated from the and water valve at the nozzle; and even switched patented bulk moist sand pile and cement mixture water pumps to increase the water pressure at the designs that had worked for over 50 years by the nozzle, which I thought would solve my problems. Cement Gun Company and their licensees. With It never dawned on me the one key element the use of the dry bagged material instead of using missing was the moisture in the mixture before moist sand and cement mixture, it became neces- entering the gun. By taking a mortar mixer and a sary to predampen the material before it entered water spray nozzle to predampen the dry material, the gun. By mixing moist sand (with 3 to 5% we made a crude predampener, which brought the Shotcrete • Fall 2015 13


2015FallShotcreteEMag
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