Concrete: Keyway

So a keyway or a key in concrete construction is basically a lock, a way of locking two separate concrete pores that are, sorry, that are two concrete members that are poured separately. Here we can see this little notch here in this concrete grade beam. This notch here is the keyway. And we can see how it's constructed. They put a 2x4 or a 2xmember or whatever size member they want. And they run the rebar through the formwork. And then they pour this one. They pour this portion. But the rebar is sticking out. And this one will make a key way such as that. So it is essentially to join two separate pores. In this case, maybe there's a two by four that is laying in there. And it is making this groove. So that when a wall comes in, it's going to look something like this. Here's the wall. And there's that additional piece sticking in the foundation, joining the wall to the footing. So in this example, these pockets, these pockets change colors. These pockets are going to, when this half or when this portion is poured, the concrete will go in these pockets and locks it. so that vertically the two pores cannot move one with respect to the other. In retaining walls, it is very popular to have a keyway, and we've seen it in drawings mostly, and it looks something like this. You have like a cantilever retaining wall, and this cantilever retaining wall looks like that. It's got a heel, it's got a toe, it's got a stem, but then they go in there and they pour a little bit of extra in there to lock it in the ground. They might put a French drain, backfill, and there is dirt all the way here. So looking at this image, that hole that we have in the ground is pretty much a key way. So I have here, I have some concrete that's going to be poured here and a stem. And it's going down in the ground a little bit. And then there's a little bit back there. And then they will backfill over here. There is rebar going in. Let me draw the rebar. There is rebar going in, and there is rebar continuing down into the keyway. And there is rebar on the heel. There is a whole video on placing rebar in a cantilever retaining wall. Please take a look at that. But essentially, I was just showing the keyway here, so that if this wall is pushed by the dirt that it's retaining, then the keyway will keep it from sliding. That's the function of a keyway in cantilever retaining wall or any other form of retaining wall versus a keyway in a concrete pore between two separate pores is basically to lock the two together.