5
$\begingroup$

So I just got back from watching an episode of the Science Channel program Unearthed, a show focusing on archaeological discoveries. In the episode in question, the subject was on the Lighthouse of Alexandria, and one of the questions asked in the episode is how the lighthouse stood true in an earthquake hotspot for 1500 years. One theory was that the granite bricks were connected by a kind of mortar made from molten lead. A demonstration had been tested, and it turns out that a wall of granite bricks and molten lead mortar can withstand seismic shock without problem.

Now, obviously, lead is not a metal worth recommending, considering its toxic nature, but are there other metals or alloys that, when still molten, can be used to make mortar? And would it be practical to use them given today's technology?

$\endgroup$
  • 2
    $\begingroup$ I'm not sure I see a worldbuilding question here. $\endgroup$ – user535733 Aug 6 at 2:57
  • 1
    $\begingroup$ I suspect that lead was used because it has a low melting point and because its malleability would allow for some energy absorption between the blocks rather than simply cracking like Iron would. So, I suspect that your answer is gold, but I'm not convinced that's commercially viable. $\endgroup$ – Tim B II Aug 6 at 3:41
  • 1
    $\begingroup$ I'd seriously doubt that molten lead could be used as mortar, since it would almost certainly solidify before you could put another brick on top of it. (And you'd have an awful lot of burned masons...) What might be possible is to use lead strips between the blocks, similar to the way lead is/was used to join pieces of stained glass. $\endgroup$ – jamesqf Aug 6 at 4:25
  • $\begingroup$ Isn't "molten metal mortar" just welding? $\endgroup$ – Psylent Aug 6 at 4:59
  • 1
    $\begingroup$ @Psylent, it's called brazing $\endgroup$ – L.Dutch Aug 6 at 5:23
5
$\begingroup$

Bi58, with a little help.

An alloy of bismuth and tin in the proportion 58:42 known as Bi58. by itself has a melting point of 138 °C (280.4 °F), but doesn't by itself have suitable properties to act as mortar, as it needs to be able to stay where it's troweled to and although denser needs the approximate properties of a well-whipped egg-white.

The builder's mate would need to either use a spot-board and shovel or a powered rotating mixer and add-in a goodly proportion of copper powder and a little flux (to aid wetting), this will give the desired properties. A rotating mixer might just be easier to maintain at the right temperature and small batches would be be ferried to the (brick) layer as needed.

On cooling, the mixture expands by a small percentage (1 or 2%) which gives a good grip on the surfaces of rough materials. It has the virtue of being fine with the day/night cooling cycle, so will stay intact over time.

$\endgroup$
4
$\begingroup$

Using metal as binder between non metallic part is a knowledge we humans are using for quite some time. We still use it today in Kintsugi.

In the case of Kintsugi, however, gold particles are added to the binder, instead of melting the gold itself.

What would be the requirements for such a metal to be used as binder?

  • non brittle, to yield when (dynamic) loads are applied and possibly damp them
  • low melting point, to prevent that the high temperatures alter the other substance
  • resistant to oxidation, to prevent that in few years the binder is turned to dust

The above leave not many alternatives to lead, I am afraid.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.