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2013FallShotcreteEMag

you will drive the operator crazy by having to shut tures and water are both based on the rate of down the machine too often. Setting the correct cement delivery. So if belt speed is changed, the belt speed is something you will learn over time water and admixtures need to be changed to with some trial and error. I find that we shoot most maintain the same final concrete mixture design. walls and thin surfaces slower than we shoot floors Once calibration is complete per the guidelines, and thick walls, so I adjust the belt speed slightly you should be ready to start mixing and pumping. to meet the production rate the application requires. It makes it easier for the operator if he Loading Operations doesn’t have to stop and start the batch plant to There are two main ways to use a volumetric keep the pump hopper from overflowing. Never batch plant. One way is by filling the truck with adjust conveyor speed mid-job unless you are all the materials at a facility and transporting the ready to do some recalibration too. Since the unit to the job site, where it is emptied and then cement is delivered at a fixed speed, the admix- run back to refill. The other way, which is the way we do it, is to set up the volumetric batch plant at a job site, park a portable cement silo and excavator next to it, and continuously batch throughout the job (refer to Fig. 2 and 3). Our batch plant is a stand-alone unit mounted on a trailer with a motor to supply hydraulic power. We only use this unit on larger jobs that will take at least 3 days or require over 130 yd3 (100 m3) of material because mobilization is a little costly. Regarding manpower, we have one crew member who oversees the volumetric batch plant and the shotcrete pump. However, the nozzleman still has ultimate control over the shotcrete pump via a remote control. The batch plant operator also has support from the excavator operator, who keeps the batch plant properly fed with cement, sand, stone, admixtures, and water. Using volu- metric batch plants would work incredibly well for big projects that are far away from a ready- mix plant. Advantages of On-site Volumetric Batching versus ready-mix Fig. 2: Batch setup There are many advantages of volumetric batching on site over plant-produced ready-mix. I understand a lot of shotcrete contractors in many parts of the country have no problem dealing with their local ready-mix companies. Unfortunately, that does not seem to be the case in our part of the country. I often find it difficult to deal with the ready-mix companies, especially on a job where you want to shoot 60 to 80 yd3 (45 to 60 m3) a day and are often requesting short loads with less-than-maximum truck capacity. Some ready-mix trucks may take a little longer than others. On site, when shooting shotcrete, if there is a small issue that delays the shooting, one can find that several concrete trucks are very quickly waiting in line. With the volumetric batch plant, our crew leader doesn’t even have to think about the mixture and can concentrate on his job, which is to shoot and finish a good project. The batch plant can produce material as fast or as slow as you want it, so you never have to worry about Fig. 3: Alternate view of equipment setup shooting speed and backing up trucks. Hot loads 20 Shotcrete • Fall 2013


2013FallShotcreteEMag
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