»About the Cement Industry
Why is the industry concerned about sustainability?
The industry produces 1.5 billion tons of cement annually-a 'glue' which holds together much of our modern global infrastructure; from roads to houses, from dams to water treatment systems, from schools to hospitals. It is hard to envision a society without cement. However, the industry must deal with a number of concerns:
- restoring exhausted limestone quarries,
- minimizing wastes and
- releasing or producing carbon dioxide in its manufacturing processes.
- local impacts from cement dust, noise and traffic.
There are also opportunities, such as recycling the waste of other industries in an environmentally responsible way.
For example:
In manufacturing 1500M tonnes of Portland cement each year worldwide, an equivalent amount of CO2 is released into the atmosphere. A considerable degree of mitigation can be achieved by adopting principles of sustainable waste management, not only by reducing emission of CO2 at source, but also by reusing or recycling it where possible. Significant reduction might be achieved by:
- Burning alternative fuels;
- Extending cement with supplementary materials;
- Using low grade, low energy cements;
- CO2 stripping from gas stacks;
- Developing CO2 neutral and geo-polymer type cement systems;
- Promoting carbonation of cementitious materials.
From: Center for Contaminated Land Remediation
How is cement produced?
Cement is made by crushing and blending limestone (calcium carbonate) and other materials containing silicon, aluminum and iron oxides. The blended material is heated at extremely high temperatures in a kiln where the compounds react. Products leave the kiln as a nodular material called clinker, which is then cooled and ground with small portions of gypsum and other additives to produce cement. Finally, cement is combined with sand, gravel and water to form concrete-the product most of us see in our daily lives.
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