Eco-Cement is a brand-name for a type of cement which incorporates reactive magnesia (sometimes called caustic calcined magnesia or magnesium oxide, MgO), another hydraulic cement such as Portland cement, and optionally pozzolans and industrial by-products, to reduce the environmental impact relative to conventional cement. One problem with the commercialization of this cement, other than the conservatism of the building industry, is that the feedstock magnesite is rarely mined.
Ordinary Portland cement requires a kiln temperature of around 1450 °C. The reactive magnesia in Eco-Cement requires a lower kiln temperature of 750 °C, which lowers the energy requirements, and hence the use of fossil fuels and emission of carbon dioxide (CO2).
Eco-Cement sets and hardens by sequestering CO2 from the atmosphere and is recyclable. The rate of absorption of CO2 varies with the degree of porosity and the amount of MgO. Carbonation occurs quickly at first and more slowly towards completion. A typical Eco-Cement concrete block would be expected to fully carbonate within a year.
Eco-Cement is able to incorporate a greater number of industrial waste products as aggregate than Portland cement as it is less alkaline. This reduces the incidence of alkali-aggregate reactions which cause damage to hardened concrete. Eco-Cement also has the ability to be almost fully recycled back into cement, should a concrete structure become obsolete.
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