A real chance to become more by production environmentally friendly Green Cement of and uses
The use of modern day cement contributes to two billion tonnes of CO2 annually into the atmosphere, which makes it the third largest man‐made source of CO2.
The cement releases such large amounts of CO2 because of two main reasons. The first is because to get Portland (normal) cement, calcium carbonate is heated until calcium oxide is formed (which is needed for the cement) producing the bi‐product of CO2. The second reason is that to get calcium oxide from calcium carbonate, excessive amounts of heat is needed, which requires the burning of fossil fuels (Sun et al., 2007).
To tackle this problem, Professor Jannie van Deventer and his team from the University of Melbourne have developed a cement that uses an aluminium‐silicon based system instead the traditional calcium based system that does not result in the release of CO2. This cement, known as Geopolymer cement, or ‘Green cement’, uses waste materials such as fly‐ash from coal fired powered stations, and slag from the production of iron. The fly ash and slag is then mixed with traditional materials such as sand and water to form the basic concrete.
An alkaline solution is then added which dissolves out aluminium and silicon molecules from the fly ash and slag to form geopolymers, the geopolymers then link together to give the concrete its strength.
This makes geopolymer concrete ideal in countries where there are extreme temperatures, of situations where resistance to salt, fire, acid, snow, pH are critical. Professor Jannie van Deventer and his team, has been around since the 1950’s in the Soviet Union where Professor Glukhovsky originally discovered geopolymer cement. This cement used an alkaline solution as a reactor but only slag (no fly‐ash) was used. The cement was used to build the majority of buildings in the Ukraine back then which are still standing and showing no sign of deterioration (Duxson et al., 2007).
In the not‐so‐distant future it is likely that the changing national and global environmental laws in regards to C02 emissions will force the Portland cement and concreting companies to convert to more sustainable and the answer just might be ‘green cement’. As a result, the development of geopolymers to replace some of the Portland cement is a topic of high interest.
Further more studies to evaluate local materials from Yemen and then subject different combinations to a variety of tests to determine the optimum concrete mixture. “Green” construction optimizes the available local materials and seeks methods to perfect the durability of the structures.