Ancient Walls of our Ancestors

For many years, as an Engineer, I have puzzled about how our ancestors constructed massive structures such as the Pyramids, Angkor Wat, the Coliseum at Ephesus, Giant walls of Butrint, Machu Piccu and so on.  My photos below are just one example, showing part of the Greek walls of the Coliseum of Ephesus.

"Features" shared by the blocks that form many ancient structures are:

- More than 2 cubic meters in volume

- More than 5 tonnes in weight

- Perfect fit with no gap between blocks

- Irregular polygonal shapes

- Occasional surface defects with bulges on the surface of the blocks

Most archaeologists have asked questions like "where did they quarry them", "how did they lift them", "why did they carve random bulges on the surface", "how did they machine them to get such a good fit"

The questions themselves are wrong. Our ancestors did none of those things.  Instead, our ancestors made aggregates into liquid concrete, and poured it into a mould ... which was a growing pile of clay that they added to the face of the wall that was under construction.  The concrete was poured directly against at least two adjacent "blocks" that had already set, forming perfect joins.

As you can see e.g. in the photos from Ephesus, there are occasional surface defects called "drops".  This is where the clay false wall had not set perfectly and the concrete was able to protrude into the clay before the concrete set.

In Egypt, the builders took time and trouble to "face" the blocks and remove imperfections while the blocks were still slightly damp.  This could be done with wooden tools, and the surface of the blocks could also be easily decorated with writing and pictures before each block was fully set.

In Ephesus, the ancient Greeks pushed iron rods into the top of one block while it was wet, and then cast the next block on top.  Over the last 2700 years the iron has rusted and "exploded" causing many of the blocks to split.  This is a common problem when iron is used to reinforce concrete, in conditions where water seeps in later.

For a vertical wall higher than 8 meters, the pile of clay used to form the "mould" for the next layer of blocks starts to collapse under its own weight.  Therefore, many ancient structures have stepped walls.  Each layer is a more convenient height of between 1 and 3 meters.  The clay mould forms the side of a pyramid while structural integrity is provided by concrete, poured one block at a time, carried in buckets.

Some walls were built by our ancestors with (small) quarried blocks and bricks ... sometimes interspersed with mortar.  These walls tended to be vertical and short lived.

Other walls, often the oldest and most resilient ones, were similar to the examples in the pictures. These walls tend to slope at an angle of between 20 and 40 degrees ... because this was the best angle to support the growing mound of earth and clay that formed the temporary retaining mould until the concrete blocks set.

The famous "Unfinished obelisk" is cited by many as an example of use of unknown technology in a quarry by the ancients. But if it is carved out, it would be formed from the same material as the surrounding sandstone.  However, the base of the obelisk is uniform in color with no stratification.  The sandstone above and below it is stratified with different color to each strata.  The obelisk is  therefore made of a completely different material than the soft sandstone around it.

In fact, the "quarry" was a massive sandstone and clay mould and the obelisk was made of a concrete mixture, cast into the mould but which cracked during drying.