Page 29

2016WinterShotcreteEMag

Fig. 4: Nozzling in good form with a great view Logistics and the Dry-Mix Process There was a beautiful home with construction well underway in between the staging area for our batch trucks and the pool. Although the hardwood floors, interior paint, and trim work were all complete in the house, we needed to run our lines through the middle of the house. Overall, we needed approximately 300 ft (90 m) of delivery lines to get our shotcrete to the pool. Using the dry-mix process, our hoses don’t surge like a hose from the wet-mix process, so there was less risk of damaging the floors; that said, we still protected the floors with thin plywood and plastic. Also, the dry-mix hoses run much less pressure than a wet-mix pump, so the risk of a hose bursting and spraying the interior ceilings with the shotcrete materials were minimized. Being such a technical project, we decided to shoot the floor first, followed by the walls and other details on Days 2 and 3. Dry-mix shotcrete was the perfect application method (Fig. 4 and 5). We are able to start and stop as needed to focus on the details and not worry with scheduling concrete trucks because the shotcrete material isn’t hydrated until exiting the nozzle. It is mixed with water on demand as needed. To continue over multiple days, our crew members benched off material at ideal stopping points and maintained clean reinforcing bar through the use of a blow pipe both during the shoot as well as between shoots to aid in cleanup. All surfaces were maintained in a saturated surface-dry (SSD) state while shooting onto previously shot areas. In addition, the crew members are versed in removing laitance from the hardened surface and providing the optimum surface for shooting a subsequent layer the following day. The large volume of air in a dry-mix rig, along with the water at the nozzle, can provide a strong air-water blast that’s great for cleanup and also for wetting the surface to provide an SSD condition when not sending material through the lines. The downside of the dry-mix method is that more care is needed in material handling. With wet-mix shotcrete, it doesn’t matter if the aggregate is wet before it is mixed because water is being added to the mixture anyway. With the dry-mix method, too much moisture in the sand can be problematic or even shut down the job. In our case, we typically stockpile large quantities of dry sand (3 to 5% moisture content) at our yard and reload at our own facility or a satellite yard. On this job, being in a remote location in the mountains of North Carolina, that was not an Shotcrete • Winter 2016 27


2016WinterShotcreteEMag
To see the actual publication please follow the link above