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How SupaBlok™ can help reduce greenhouse gasses

Cement has been singled out in recent times as one of the major contributors to the increase of carbon dioxide in the atmosphere. Cement manufacturing is a high energy emissions intensive process. The manufacture of cement releases greenhouse gasses both directly and indirectly. The heating of limestone, an ingredient in the production of cement, releases carbon dioxide directly while the burning of fossil fuels to heat the furnace indirectly results in the release of carbon dioxide.

The direct emissions of cement occur through a chemical process called calcination. Calcination occurs when limestone, which is made of calcium carbonate, is heated, breaking it down into calcium oxide and carbon dioxide. This direct process accounts for half of all emissions from cement production.

Indirect emissions are produced by burning fossil fuels to heat the furnace. To make cement, limestone and other materials are heated in a furnace at about 1400°C then ground to form a coarse solid substance called clinker. Clinker is then mixed with gypsum to form cement. The furnaces is typically heated by oil, coal, or natural gas and the combustion of these fuels produces additional carbon dioxide emissions. These indirect emissions represent about 40 percent of all cement emissions. 

Finally, the electricity used to power additional factory machinery, and the final transportation of the cement, represents another source of indirect emissions and about 5 to 10 percent of the industry’s emissions.

Relative to regular concrete blocks or concrete masonry units (CMU), SupaBlok™ can contribute to the reduction in carbon dioxide emissions in two important ways: better thermal insulation and reduced cement usage.

SupaBlok™ is made of cellular lightweight concrete (CLC), an aerated concrete with a high percentage of air filled pores. Because of the presence of air within this lightweight concrete its thermal insulating properties are very good compared to regular concrete. SupaBlok™ having a density of 600 kg/cu m has a thermal conductivity of 0.11W/mK while CMU having a density of 2,000 kg/cu m has a thermal conductivity of 1.2 W/mK. This means that a SupaBlok™ wall is about 11 times better at insulating than a concrete block of similar thickness. For homes built with SupaBlok™ this results in less air conditioning and less electricity usage contributing to fewer ozone depleting and fewer carbon dioxide gasses released to the atmosphere.

SupaBlok™ having a density of 600 kg/cu m uses a little less cement than a CMU block of comparable size. However, there is an opportunity to further reduce the cement content in SupaBlok™ relative to CMU. There are materials available which act like cement but are either naturally occurring or are waste products that need no additional processing before use. The lack of additional processing means that no energy is consumed and no greenhouse gasses emitted in preparing them for use in concrete. These alternative cementitious materials include fly ash, ground granulated blast furnace slag (GGBS), limestone fines and silica fume. Cement is typically processed on a large scale in a very controlled manner. As a result, its properties are very consistent and predictable. Waste products such as fly ash and GGBS are not controlled and have significant property variation. When used in producing CMU consistent cement properties lead to consistent properties in the CMU block itself. As a structural component in a monolithic wall the strength of CMU blocks needs to be consistent. Given that SupaBlok™ is a form (and not a structural component) enclosing a column and beam structure, its strength is much less important and as a result it is much more able to tolerate variation in its properties and its constituents’ properties. Consequently, SupaBlok™ is much more tolerant of the inconsistencies of alternative cementitious materials than CMU. This advantage makes it possible to use even less cement in making SupaBlok™ than you would in making CMU thereby reducing carbon dioxide emissions.