As clinker is the most energy and CO2 intensive component of cement, blended alternatives to Portland Cement with lower clinker-to-cement ratios are an effective way of reducing energy consumption and CO2 emissions. Materials such as granulated blast furnace slag, fly ash, natural pozzolans and limestone show hyrdraulic and/or pozzolanic activity or filler properties and are therefore suitable for use as clinker substitutes. In certain cases they can also contribute positively to cement performance.
The following six factors affect the use of other constituents besides clinker as cement blends:
| Technology or Measure | Energy Savings Potential | CO2 Emission Reduction Potential Based on Literature | Costs | Development Status |
|---|---|---|---|---|
| 粒状高炉矿渣水泥 |
For a cement containing 30 to 70% of GBFS, energy consumption can be reduced by 0.42 to 1.88 GJ/t-cement.
|
For a cement containing 30 to 70% of GBFS, CO2 emissions can be reduced by 100 to 430 kg per every ton of cement. |
Investments necessary for retrofitting existing plants are estimated to be in the range of € 5 to 10 million (US $ 7 to 14 million) | Commercial |
| Cement with Fly Ash |
For every ton of clinker substituted, energy needed for clinker production can be saved (GNR World Average: 3.58 GJ/t-clinker) |
For every ton of clinker substituted, CO2 emissions associated with its production can be avoided (GNR World Average: 855 kg/t-clinker) |
Not available | Demonstration |
| Cement with Pozzolana |
Thermal energy use decreases by 0 - 600 MJ/t cement; electricity use decreases by 0 - 25 KWh/t cement. |
The process-related emission reduction in the range of 0.52 tonne CO2 per every tonne of clinker replaced by pozzolana is possible. |
|
Commercial |
| Limestone Portland Cement |
|
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Capital costs for extra storage capacity for the other main constituents and the new cements as well as the technical equipment for handling and drying of these constituents may be € 8-12 million. |
Commercial |
The report represents the independent research efforts of the European Cement Research Academy (ECRA) to identify, describe and evaluate technologies which may contribute to increase energy efficiency and to reduce greenhouse gas emissions from global cement production today as well as in the medium and long-term future.
In India, reductions in thermal energy demand in the range of 0.85-2.0 GJ/t-cement are reported. 
Investment cost for retrofit is estimated to be € 8 to 12 millions. Capital costs are due to extra storage capacity for the pozzolana and the cements as well as the technical equipment for handling and drying of the pozzolana.