[EvaH (OP)]

Paul asks:

Why we don't use more rocks to build buildings - as they have in Edinburgh and as they are now with the Sagrada Familia in Barcelona - with stone from Lancashire? They crush test the rock, but could ground penetrating X-rays be used to test for fissures in the rock?

Can you help?

[evan_au]

could ground penetrating X-rays be used to test for fissures in the rock?

It is true that X-Rays do penetrate materials much farther than (say) light.

If you wanted to detect fissures from the surface, you actually want to use something that bounces a signal back to the surface so you can measure it. Unfortunately, X-Rays penetrate so well that they also penetrate fissures and cracks, and keep going on into the Earth until they are absorbed by the bulk of the Earth. You won't get much of a signal bouncing back to the surface.

Perhaps it might be better to use something like ultrasound, which will bounce back to the surface from changes in consistency (like cracks or fissures)?

the Sagrada Familia in Barcelona

I visited it when it was much less complete than it is now. My impression at the time was that it used a lot of concrete.

Apparently, the older parts use sandstone, and the newer towers use granite with steel reinforcing.

I guess when you have been building something for over a century, techniques change during construction...
See: https://www.iom3.org/materials-world-magazine/feature/2017/jul/03/material-marvels-basilica-de-la-sagrada-familia

[alancalverd]

You can x-ray bricks and building blocks in principle but whilst this will reveal large fissures or even small cracks (with a CT scanner) it is slow and doesn't really predict the crush strength. Far better, quicker, cheaper, safer and actually predictive is to load the block in a hydraulic press.  Or use steel and concrete which can be manufactured to a consistent specification. 

[Petrochemicals]

Paul asks:

Why we don't use more rocks to build buildings - as they have in Edinburgh and as they are now with the Sagrada Familia in Barcelona - with stone from Lancashire? They crush test the rock, but could ground penetrating X-rays be used to test for fissures in the rock?

Can you help?

Ultrasonic testing, rebound hammer, destructive testing (crushing) are some of the tests to assertain the quality of concrete and stone. One piece of sandstone in a wall can crumble yet the piece next  to it could survive indefinatley, all pieces being the same age. I am not sure of edinboroughs stone but I guess it is much like the granite aberdeen is famous for. Granite is very hard to work, which is why aberdeen is a marvel from a technical point of view, sandstone limestone is easy to carve, but this is why oxford is in a state of constant disrepair, little point carving it at all as any detail is quickly lost, just see the cathedrals.

Stone is expensive though, thats the reason, bricks these days are too expensive, but not as bad as stone.