Abstract
To reduce CO2 emissions from the building industry, one option is to replace cement in specific applications with alternative binders. The Carbstone technology is based on the reaction of calcium- and magnesium-containing minerals with CO2 to form carbonate binders. Mixes of carbon steel slag and stainless-steel slag, with tailored particle size distributions, were compacted with a vibro-press and subsequently carbonated in an autoclave to produce carbonated steel slag pavers. The carbonated materials sequester 100–150 g CO2/kg slag. Compressive and tensile splitting strength of the resulting pavers were determined, and the ratio was found to be comparable to that of concrete. The environmental performance of the Carbstone pavers, with an average tensile splitting strength of 3.6 MPa, was found to be in compliance with Belgian and Dutch leaching limit values for construction materials. In addition, leaching results for a concrete mix made with aggregates of crushed Carbstone pavers (simulating the so-called “second life” of pavers) demonstrate that the pavers can be recycled as aggregates in cement-bound products after their product lifetime.
Highlights
Cement is the second most consumed material by mankind, after water
Cement typically constitutes 10 to 15% of concrete, and concrete has one of the lowest embodied energy demands per volume among materials [3], cement ends up being responsible for 5–10% of global CO2 emissions due to its massive scale of production [4]
Unlike for other energy-intensive processes, CO2 emissions in cement production are mainly derived from the decarbonation of raw materials, i.e., limestone, and only 40% of the CO2 emissions are related to energy [2,6]
Summary
Cement is the second most consumed material by mankind, after water. About 4.1 Gt of cement is produced each year [1]. Cement typically constitutes 10 to 15% of concrete, and concrete has one of the lowest embodied energy demands per volume among materials [3], cement ends up being responsible for 5–10% of global CO2 emissions due to its massive scale of production [4]. Under a Business as Usual scenario, the cement industry may become responsible for up to a third of anthropogenic CO2 emissions by 2050, as a result of increased demand in developing countries and CO2 mitigating actions taking place in other sectors [5]. Unlike for other energy-intensive processes, CO2 emissions in cement production are mainly derived from the decarbonation of raw materials, i.e., limestone, and only 40% of the CO2 emissions are related to energy [2,6]. The use of green electricity or refuse-derived/biofuels can only partially mitigate the production emissions
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