Volcanic materials (sometimes called "Natural Pozzolans") have been used as a cement material ever since Roman times
In a low energy, two step mechanical process, supplemental cementitious materials, e.g. fly ash/volcanic ash, steel slag, or combinations thereof, are processed in specially-configured rotating and vibrating ball mills where:
NOTE: The first step is about particle size, the second step is about mechanical surface activation, thus these are two completely different forms of processing.
The result is significantly increased amorphization and thus chemical reactivity of the powder particles. Over 70% Portland cement (OPC) replacement is achieved.
There are around 70 trillion tonnes of volcanic ash deposited from large eruptions, distributed globally.
Volcanic ash is easy to quarry, with a soft, easy-to-grind structure.
The use of natural pozzolans as an alterntive to cement in U.S. critical infrastructure is beyond doubt. The difference is replacement rates have typically been no more than 20% (PDF here). And unlike the Romans, modern builders do not have the months required for natural pozzolanic cement to set.
But for EMC Volcanics at 70% replacement? No problem! Time-pressure and modern methods such as slip-forming require modern concrete mixes to develop high strength in days, not months. EMC Volcanics can meet that need even at 70% repelacement!
Workmen casting concrete made from Energetically Modified Cement