Could Roman concrete have clues on how Pyramid of Giza was built – and saved?

The enduring mystery of how the ancient Egyptians built the Great Pyramid of Giza – with its 2.3 million multi-tonne stone blocks – has puzzled researchers for centuries. Mainstream archaeology holds that the pyramids were constructed from natural limestone or granite blocks precisely cut and hauled into place. An alternative scientific theory suggests the blocks might have been cast from an early