Concrete is actually just one of the many applications of cement. Cement is a mix of lime and water that is an excellent binding agent, first discovered by the ancient Macedonians some 3,000 years ago. The discovery ranks with fire, the wheel and sliced bread among the great game changers in human history.
If cement is mixed with gravel, it becomes concrete, billions of tons of which are poured annually into buildings, roads and other infrastructure. In other configurations, it becomes mortar or plaster.
The manufacturing process of cement is highly energy-consuming: to turn the raw material, limestone or chalk, into lime, it has to be heated to temperatures exceeding 2,000º F for about ten hours. The heat is predominantly produced by burning coal. Coal burning produces CO2 and in the case of cement, the ratio is 1:1. For every ton of cement produced, one ton of CO2 goes up into the air. Globally, 4,000,000,000 tons of cement or produced every year, accounting for about 6% of the total global CO2 emissions.
What if we could make cement without all that heat?
David Stone, working on his graduate degree as an environmental scientist at the University of Arizona in the 1990’s, found a way, using iron as the base material instead of lime. The process he invented is so chemically reactive, that no other energy input is required. Then he found also that his compound would readily bond with silicate, a.k.a. glass, creating a cement with as much as 5x the strength of regular ‘Portland’ cement. Moreover, not only does this new type of cement, called ‘Ferrock’, not produce any CO2, it actually absorbs it.
By a serendipitous turn of events, he was invited to the Tohono O’odham Community College to talk to its students about sustainability. And there, he met Richard Pablo.
The degradation and dispossession inflicted upon Native Americans in the 18th and 19th century is still manifest today. One grave consequence is that the rate of alcoholism is extremely high among them. Alcohol is absolutely prohibited on the reservations., but just outside the reservations, along the highway, there are entire fields of empty bottles giving witness to the distressed condition imposed upon them.
In his younger years, Richard Pablo was one of the many who left their empties there. But he turned his life around and started looking for a constructive way to spend his days.
Then he met David Stone, who was looking for glass. Richard knew where to find glass. Moreover, he was able to translate David’s scientific approach into concepts acceptable to the Tohono and draw them in to the endeavor of collecting it.
Now the fields of glass are being cleared by the seventh generation and the debris is ground into the powder that lends David’s iron-based cement its tremendous strength.
The Weekly Green spoke with David Stone about his invention, his collaboration with Richard Pablo, and the meeting of modern science with ancient culture.