Tag Archives: CO2 emission

The Importance of Cement and its Future

Concrete is the most used material in the world because of its cheap price and large quantity. It is needless to say concrete is made of cement. However, cement is also a criticized material by the public, for its intensive CO2 emission from production process. The production of cement accounts for about 5-8% of the non-natural CO2 worldwide.

Importance of Cement

Importance of Cement

Importance of Cement

People may ask, can we find an alternative construction material instead of cement? such as wood, steel. The annual usage of wood is much above the replanting level, and it is not possible to get wood in some places such as Africa and China. As for steel, it is costly and again the production of steel also gives CO2 emission. Furthermore, the production of cement is not that energy intensive compared with other materials.

Importance of Cement

Actually, it is not possible to find an alternative construction material. 98% of the earth’s crust is made of eight elements: O, Si, Al, Fe, Ca, Na, K, Mg, which are the main elements of cement as well. From the long term run, the world will still need a large amount of cement. The demand of cement mainly comes from developing countries, such as India and China because of the urbanization and its population growth.

Importance of Cement

Importance of Cement

Importance of Cement

Since we have to use cement in the future, how can we do to reduce the CO2 emission and what is the future of cement? Efforts have been doing ever since decades ago in the cement industry and research community.

On the one hand, cement plants nowadays burn (hazardous) waste, say, car tyres, as fuel to make cement. The wood floating on the water of Three Gorges Dam is even collected to make fuel for cement plants. On the other hand, the production process of cement has always been optimizing. Some cement plants can even reach 80% efficiency, which is a great achievement even from a theoretical standpoint.

Importance of Cement

Importance of Cement

Researchers of cement try to use less cement clinkers. One viable method is Supplementary Cementitious Materials (SCMs). SCMs are commonly industry by-products or raw materials, such as Slag, limestone, Fly ash, silica fume, natural pozzolan. Whether binary blended or even ternary blended, SCMs can replace part of cement without sacrificing equivalent engineering properties.

Importance of Cement

Considering the limited quantity and access of SCMs, SCMs are not a permanent sustainable way from a long term run. Some researchers are trying to utilize the unlimited amount of calcined clay, for the kaolinite content of clay has similar cementitious property. Work done replacing 30% of cement by calcined clay in Cuba shows the potential future of clay if well used.

Importance of Cement

Generally speaking, cement is a significantly important construction material, and it is not necessary to worry that much as for the CO2 emission in the future.

The worldwide cement output is decreasing in 2012

As reported by China Daily, the official Chinese newspaper in English, China’s cement output growth drops sharply in the first five months. The output grew 5 percent from a year earlier to 793.98 million tons; however, the growth rate represented a sharp decrease of 14.3 percentage points from the same period of last year, showed by the National Development and Research Commission.

The reason accounting for the dropped output of cement is the economic slumps both at home and abroad, which dampened market demands. The strict regulation and control on domestic real estate by the government further reduced the demand of building materials as well. The latest news of Sany company (Sany Group loses 30% of workforce: report) also confirmed the harsh situation of construction industry in China.

construction-china
Construction everywhere in China.

Since China is a fast growing market of construction industry, the cement output decrease in China may also indicates the cement drop of the whole world. Because of the struggling economy worldwide and the increasing demand of less CO2 emission of cement, scientists of cement industry should spare no effort to focus on the research of cementitious materials, such as slag, fly ash and limestone blended cements, which have economic and environment benefits.