3:1:1:1

[stonecutter]

Re: 3:1:1:1

Most architects and nearly all engineers specify mortar too strong for the units being laid...

Most of the ones I have met do. One reason you see severe degradation in new and 'restored' stonework.

[stonecutter]

Re: 3:1:1:1

Exactly - no cement, no lime = very lean to me, because I don't see clay as a permanent binder unless you can get it hot enough to "fire". Until then its a reversible thing that must be protected from moisture, etc.

Permanence is ambiguous with natural products. The way clay is used effects how it performs...and what the final result is. Understanding how natural products work and the way to use them is the challenge.

But that's fine, see it the way you want.

[david s]

Re: 3:1:1:1

Exactly - no cement, no lime = very lean to me, because I don't see clay as a permanent binder unless you can get it hot enough to "fire". Until then its a reversible thing that must be protected from moisture, etc.

As clay is composed of decomposed rock, millions of years old, it is essentially superfine sand (an aggregate) but because the particles are so fine they attract one another. This is what gives the clay it's strength, but it is still only a mechanical bond. It hasn't changed chemically (like cement or lime) until it gets fired (over 573 C) I think the moisture protection thing is not too much of a problem. Clay with quite a high moisture content is still as strong as fully dried clay. In some cases I think it is actually stronger. Try smashing a block of partially dried clay compared to a fully dried one. Clay is also used to line dams to create a waterproof layer to hold the water in. Pretty versatile stuff.

[Tscarborough]

Re: 3:1:1:1

The strong points of clays are generally when they are wet (sealing reservoirs) or kilned (brick). In between they are unstable, and subject to large swings in volume.

[david s]

Re: 3:1:1:1

The strong points of clays are generally when they are wet (sealing reservoirs) or kilned (brick). In between they are unstable, and subject to large swings in volume.

But it's the in between parts that you can do beautiful things with the stuff. Free and abundant, it's a god given substance.

[stonecutter]

Re: 3:1:1:1

89 Posts later has anybody actualy answered poor Gianluca question????

Gian, I hope you have not hanging by your thumbs waiting!!!!

Did you miss post #3?

[stonecutter]

Re: 3:1:1:1

No I didn't miss post #3

That answers the 1st part of the question!!

Yeah it did go off topic didn't it. The OP probably ran off because a bunch of kooks were talking about clay.

Why don't you enlighten him?

[david s]

Re: 3:1:1:1

Yeah it did go off topic didn't it. The OP probably ran off because a bunch of kooks were talking

Yeah, but what a great discussion!

[stonecutter]

Re: 3:1:1:1

Yeah, but what a great discussion!

I agree..even if the participants don't see eye to eye, it helps broaden the scope of knowledge.

[Tscarborough]

Re: 3:1:1:1

The fireclay has finally started to set, I think it may well work for a barrel vault, if not for a Pompeii. I am burning the test cubes today to see how it hold up, but I am sure it will be fine.

[Tscarborough]

Re: 3:1:1:1

OK, that didn't work. It disintegrated completely and did not even leave a residue on the brick, indicating zero bond strength.

[Tscarborough]

Re: 3:1:1:1

Time to test the homebrews.

[Tscarborough]

Re: 3:1:1:1

I accidentally broke the cubes, they were too big to move easily. Both stayed adhered to one side, I will see how soft they are when they cool down.

[vtsteve]

Re: 3:1:1:1

If you taper the bricks in the critical, near-vertical areas, and rely on the mortar only as 'chinking' to fill the gaps, bond strength is almost irrelevant. Although "disintegrated completely" sound bad for the clay/sand mix... if you have enough residual strength to keep the mortar from trickling out the gaps, almost anything should work (with tapered bricks). I'm a big fan of tapered bricks. Two years ago, I used Heatstop 50 -- next time I won't .

[david s]

Re: 3:1:1:1

Time to test the homebrews.

Did you read thr surface temp of the bricks with an IR. if so I suspect the reading would be quite high as it appears you have them right in the hottest part of the fire, probably hot enough to fire the clay (573 C+)