Ratio for concrete
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Speaker: OK, we're here today to make padstones for steels to sit on in our new buildings.
The basic ingredients for that would be 1 cement, 2 sand and 4 aggregate.
The ratio always stays the same.
It doesn't matter how big you want the batch. You just multiply it.
If you was making 4 times the amount we'd use 4 cement, 8 sand and 16 aggregate.
Work out the amounts
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Setting the concrete
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Speaker 1:(TO AUDIENCE) We put that into our mixer with water and pour it back out into our mould ready to set for our plots for steels to go on.
Speaker 2: (TO OTHER PEOPLE) How are you getting on then, Wayne?
Speaker 1: Yeah not too bad, Joe.
Speaker 2: It looks really good.
Did you encounter any problems when you made the concrete?
Speaker 1: Yeah, it was slightly wet so we basically, keeping to the ratio, we've added a quarter of cement, half sand and one full bucket of aggregate.
Speaker 2: Brilliant, and what's that done to the mix?
Speaker 1: That's basically stiffened the mix up ready for us to use into these moulds.
Speaker 2: So just tell me what you're going to do now then, Wayne.
Speaker 1: We're just going to level it off now, Joe.
And then use the vibrator to vibrate it down.
Speaker 2: OK, brilliant.
(SPEAKER 1 USES MACHINE)
Speaker 1: That's not too bad.
Find the weights
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Using a slump test
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Speaker 1: So Wayne, to check the consistency of our concrete to make sure it's strong enough we'll use a slump test.
To perform a slump test we use a slump cone.
Speaker 2: OK.
Speaker 1: So Wayne, what we're going to do now, we're going to lift the slump cone now it's filled up and we should see what kind of consistency the concrete has.
What we're looking for is a true slump just a natural slump in the concrete.
That gives us a nice consistency. So let's give it a go.
So what we've got there then Wayne is a nice consistency concrete.
As you can see, you've got a true slump as opposed to the concrete shearing or the concrete collapsing.
So what we can do now to test the slump of this concrete is to actually measure how far it's gone down.
Speaker 2: OK.
Speaker 1: What I should find, I should have no more than 75mm.
And what I have there is 60mm.
So we know we've got a nice strong mix to our concrete.
Speaker 2: Ok, brilliant.
Which slump test?
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