Welcome to the MedHawk Minute. Today we're talking about shotcrete.

So, shotcrete starts with the concrete truck. Now we can use a normal barrel mix concrete truck, but in this case, we're using a volumetric mixer truck. This is like a mobile batch plant, and on this truck there's water, cement, sand, and aggregate, or a rock, pea gravel, and those all get mixed together and then pumped into the shotcrete pump. What this does, they're mixing it right now, instead of having a truck that's driving from an hour away and that concrete's getting harder, we're going to mix it on demand and get just the right precision. We were to pump normal concrete into a pool, it would be too wet and it would just fall off the walls. So, this is a very special low slump concrete. It's very dry as you can see in the mix, but if it were just a hair drier, it actually get packed in the line.

These lines are being pushed under several thousand pounds of pressure, that can result in a very dangerous situation. So, we want to make sure that that mix is just exactly right. They're able to fine tune it on demand and add water or take water away in order to get it just the right slump. Okay, so the concrete gets delivered into the hopper, and then there's two large pistons down here that actually pull the concrete back up inside, just like a syringe. It pulls the concrete in and then pushes it back out the hose while the other one's pulling in more concrete. So, there's a constant action going back and forth. Then it pushes it through the S tube and back down the feeder line out to the crew. The output of the concrete pump is six inches. We neck that down to three inches, and then down here we step it down to two inch hose, and this hose goes into the pool.

So, this is the actual shotcrete nozzle. We've got the two-inch concrete coming in, and then we've got an airline coming in the top and the nozzle man is able to adjust how much air is coming out at any given time. So, that concrete comes down the line to the nozzle man, and he's actually spraying the concrete directly on the wall. After the nozzle man shoots the shotcrete onto the wall, then the guys start shaving, the top beam finishers will shave the top and start carving the walls, and then the floor finishers will do the bottom at the end. Depending on what kind of plaster we're going to put in the pool determines if we're going to float this surface smooth or leave it rough. A traditional plaster needs a rough surface to adhere all the nooks and crannies. In this case, we're putting the newest generation of finish on here. It's called skin, and it needs a perfectly smooth surface. So, that's what we're doing on this pool. This is a big job, so I'm going to help them float out this pool. We'll see you next time on the MedHawk Minute.