I have just read that Genesis mentioned the Tower of Babel being described as having "tar for mortar". I've never before heard of something as sticky and viscous as tar being used as mortar, but evidently, it was the material of choice for the Sumerians to put together their oven-baked bricks (themselves more durable than regular sun-baked bricks).

On a related note, the Romans invented concrete, which was also used to make mortar. But unlike modern concrete, or Portland cement, Roman concrete used volcanic ash as an aggregate. Using volcanic ash, the concrete gets harder as it gets older and it is even guaranteed to be waterproof. This is how the structures of the Roman Empire stood for the past 2,000 years whereas modern buildings aren't expected to last longer than 150 years in a Life After People.

So imagine that there was an ancient culture who used the following ingredients to make their mortar:

  • Tar
  • Clay
  • Powdered limestone
  • Seashells
  • Water (usually <40%)
  • Sand
  • Volcanic ash
  • Mud
  • Gravel

Would the recipe above make a good mix? Or would the addition of tar make the mixing process too difficult to even bother?

  • $\begingroup$ Chunks of asphalt rose from the dead sea, so it was an available resource. $\endgroup$
    – JDługosz
    Commented Jul 21, 2016 at 6:28
  • $\begingroup$ You really need to see Nova, S47E3, Secret of Noah’s Ark. They go into tar quite a bit, and try to modify modern commercial stuff to match the historic resource of the area. It shows how different minerals added could change its properties. And this is the same region you are interested in. $\endgroup$
    – JDługosz
    Commented Jul 21, 2016 at 6:32
  • $\begingroup$ “Romans invented concrete, which was also used to make mortar” you are mixing up your terms to produce nonsense. Concrete and morter both contain cement. Morter lacks some of the ingrediants of concrete so it's nonsense to say morter was made from concrete. $\endgroup$
    – JDługosz
    Commented Jul 21, 2016 at 6:36

1 Answer 1


No, it is as oil and water

Since tar is not water soluble it sounds like complete madness to add it into something that otherwise uses water as its solvent. You might as well ask "It is all right to mix asphalt into the mortar"?

Tar is highly viscous and sticky. It essentially works as an adhesive here. Tar is heated to make it "runny", applied to surfaces, the surfaces are joined and when the tar cools they hold together.

Mortar is something else entirely. It is cement, which hardens during a chemical process.

You are — almost literally — trying to mix oil and water here. So no, it will not work to mix in tar with other stuff to hold the bricks together. You either use tar, or you use mortar, to hold the bricks together. Not both.

  • $\begingroup$ You do know that the definition of "mortar" is interchangeable? $\endgroup$ Commented Jul 21, 2016 at 1:51
  • 1
    $\begingroup$ @JohnWDailey Was there a comment pertaining to the answer or did you just feel like being snarky? You asked: can these things be mixed. Answer: no, they cannot. How does your comment relate to that answer? $\endgroup$
    – MichaelK
    Commented Jul 21, 2016 at 1:54
  • $\begingroup$ Because you used "mortar" as if it were a separate, specific thing when the question was whether tar would make a good addition to mortar. $\endgroup$ Commented Jul 21, 2016 at 2:10
  • 1
    $\begingroup$ @JohnWDailey It would not. It can work as a watertight adhesive to the bricks on its own $\endgroup$
    – MichaelK
    Commented Jul 21, 2016 at 2:11

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