This half-baked shades of brown coloured stone with distinct layers was found among the river gravels. Obviously, it had been subjected to high pressure and temperature, such that part of the fragment was fused to form very hard surface. Certainly durable, even after soaking in the water, rubbed against other gravels and rolled in the river bed for thousands of years, it still could survive.
But if you break it apart, you will find the un-fused part of Shale and some stone fragments, which have low strengths.
That is why, if the river gravels are not screened and unsuitable materials removed, there will be localised weak spots in the concrete structure and is especially dangerous in slender columns.
Anyway, it is a beautiful natural product, but why Bergundy colour?
No comments:
Post a Comment