Cement is an important type of construction material that is necessary for almost all types of civil engineering works. Cement is the main material of concrete technology and constructions. Cement can be defined as the binding material having both cohesive and adhesive properties thereby capable of bonding the mineral fragments into a compact mass. With the growing impact of the construction industry on the environment and ecosystems, new techniques are being developed that are environmentally friendly. One such environment-friendly advancement in the field of construction is Green Cement. About 6 types of green cement are available in the present market in the world.
In general, green cement can be understood as environmentally compatible cement that is developed for minimizing the carbon footprint of cement production. Considering this, various types of green cement have been manufactured. In general practice, the manufacturing process of ordinary cement involves the production of a large amount of heat (energy) that leads to the emission of various harmful gases particularly Carbon Dioxide (burning of limestone and clayey materials at a temperature of about 1200 degree Celsius to produce clinker).
According to the statistical data, about 0.6 to 1.1 tonne of carbon dioxide is emitted for 1 tonne of cement production. The carbon dioxide thus emitted is a chief source of air pollution. Thus, to minimize such emissions and protect the degradation of the environment, the concept of green cement was developed.
Green cement is a suitable alternative to reduce such emission levels during the production by using techniques of manufacturing that significantly emit lesser levels of carbon dioxide and other harmful gases. In this regard, green cement can be defined as the cement produced by a technologically developed process that emits lower levels of harmful gases during the unit production i.e. the clinker production. Hence, green cement is also commonly referred to as the “cement produced with the help of carbon-minimizing process”.
The main benefits offered by green cement can be listed as follows:
1. Lower Emission of Carbon:
The green cement is manufactured by advanced techniques that minimize the emission of carbon levels. Green Cement reduces the emission of carbon dioxide up to 80% thereby reducing air pollution considerably.
2. Energy Efficient:
The production of green cement is energy efficient i.e. consumes lesser energy. Thus, the consumption of non-renewable resources such as coal for the production of cement is greatly reduced.
3. Utilization of Industrial By-Products and Wastes:
Green cement utilizes the various types of industrial wastes and by-products such as fly ash (a product of coal combustion process) and blast furnace slag (a by-product of the iron manufacturing process) thus make the process economical as well as saves the land required for disposal of such products.
4. Benefits to the Contractor:
Green cement has proven to be more beneficial to the Contractors than the traditional types of cement. This is because green cement does not require any additional tools and equipment. Green cement also has faster drying properties and thus the coating can be applied within 72 hours- 96 hours thereby saves the time. Such cement also provides faster curing and setting rate.
5. Longer Life Span:
Green cement has a longer life in comparison to the traditional cement as it has better fire-resistant properties as well as better resistance to deteriorating agents such as acid rain.
TYPES OF GREEN CEMENT
The common types of green cement used in the construction industry can be briefly explained as follows:
1. Magnesium Oxychloride Cement (MOC)
Magnesium Oxychloride Cement is the type of green cement that consists of magnesium oxide (MgO) powder and a concentrated solution of magnesium chloride (MgCl2) as the chief components. It is an environmentally compatible and carbon-neutral cement. These two chief components of Magnesium Oxychloride cement are the byproducts from magnesium mining. This type of green cement has enhanced setting time and also has high compressive strength. By the use of additives such as fly ash, the strength as well as the durability of MOC can be increased significantly. Moreover, the use of additives such as phosphoric acid and soluble phosphates increases the resistance of MOC to warm water.
A major drawback of this green cement is that it results in the corrosion of steel and thus is not suitable for the reinforced concrete works unless additional preventive measures are adopted.
2. Ekkomaxx Cement
Ekkomaxx Cement is the type of green cement that has been developed and manufactured by the Ceratech Company in the United States. This type of green cement comprises of fly ash (about 95%) and other additives particularly renewable liquid additives (about 5%) as the chief constituent.
Ekkomaxx cement is manufactured by the United States Green Building Code and the International Code Council and thus has zero carbon footprint. Ekkomaxx cement offers high resistance to cracking, sulphate attack as well as corrosion. It also has higher strength, resilience and durability.
3. Geopolymer cement
Geopolymer cement is also commonly referred to as the alkali-activated cement. It is the type of green cement that is manufactured using the aluminosilicates. Geopolymer cement emits 95% less carbon dioxide than the Ordinary Portland Cement.
Ferrocrete is the type of green cement that is manufactured by the mixing of two chief industrial by-products of the steel and glass industry respectively i.e. by mixing of silica and iron. When such a mixture is cured in the presence of carbon dioxide, carbon-negative cement can be produced. The Ferrocrete Cement was invented for the first time in the University of Arizona.
5. Sequestrated Carbon Cement
The Sequestrated Carbon Cement was developed by The Calera Corp. Cement in California. This type of green cement is manufactured from seawater or brine that is mixed with carbon dioxide. It may essentially be used as a substitute or alternative for the Portland cement. During the production of such cement, the carbon dioxide containing gases are filtered through seawater.
6. Calcium Sulfoaluminate Cement
Calcium Sulfoaluminate Cement is the type of green cement that reduces energy consumption by 25% and carbon emission by 20%. It has a very high setting rate i.e. 28 days strength can be reached within 24 hours. This type of cement is extensively used for the concrete works for decks of bridges and runways.