The petrification of clay by lime is an old story; even its mechanism remains unknown. The petrification of sand (clean) by Portland cement begun in the 17nd century. The product was named concrete, an artificial stone. The petrification of clay by Portland cement was and still is impossible, because the concrete remains too soft
The mechanism is known as a crystallization that give birth to three calcium silicates. The reaction calls for a good quantity of water for the crystallization: it is a petrification under water
...detail