I have just been told that tar alone makes a good enough mortar because of its adhesive capabilities.
This, however, does not change the fact that, since the Roman Empire, concrete has been the mortar of choice. Still, this brings up an interesting scenario.
True to the spirit of Life After People, this scenario focuses on what happens to a building when we vanish rather than how we actually vanished. Even though Roman concrete stood the changes of 2,000 years, most scientists doubt that in a Life After People, skyscrapers built on modern concrete would last longer than 150 years.
So in this alternate scenario, tar was the mortar of choice. For a building in a temperate climate built on bricks baked in an oven rather than by the sun (the former being more durable than the latter) and glued together by tar, how long would this building last in a Life After People? Does tar have what it takes to outdo concrete, or did the Romans make a wiser decision in inventing concrete?