Alternative Cement
Materials
Cement, a vital material for infrastructure, generates 5 to 6 percent of annual emissions. The key strategy to reduce them is to change its composition.
Rank and results by 2050 #36
Alternative Cement
| Reduced CO2: | 7 gigatons |
|---|---|
| Net cost (Billions US$): | $-273.90 |
TOTAL CO2-EQ REDUCTION (GT)
Total CO2-equivalent reduction in atmospheric greenhouse gases by 2050 (gigatons)
NET COST (billions US $)
Net cost to implement
SAVINGS (billions US $)
Net savings by 2050
Impact:
Because fly ash is a by-product of burning coal, each ton created is accompanied by 15 tons of carbon dioxide emissions. Using fly ash in cement can offset only 5 percent of those emissions. Even so, if 9 percent of cement produced between 2020 and 2050 is a blended mix of conventional Portland cement and 45 percent fly ash, 6.7 gigatons of carbon dioxide emissions could be avoided by 2050. The production savings of $274 billion are largely a result of longer cement life span.
Alternative Cement
Materials
Cement, a vital material for infrastructure, generates 5 to 6 percent of annual emissions. The key strategy to reduce them is to change its composition.
Cement is a vital source of strength in infrastructure, second only to water as one of the most used substances in the world. It is also a source of emissions, generating 5 to 6 percent annually.
To produce Portland cement, the most common form, a mixture of crushed limestone and aluminosilicate clay is roasted in a kiln. At high heat, limestone’s calcium carbonate splits into calcium oxide (the desired lime content) and carbon dioxide (the waste). Decarbonizing limestone causes roughly 60 percent of cement’s emissions. The rest result from energy use.
To reduce emissions from the decarbonization process, the crucial strategy is to change the composition of cement. Conventional clinker can be partially substituted for alternative materials that include volcanic ash, certain clays, finely ground limestone, ground bottle glass, and industrial waste products—namely blast furnace slag (from manufacturing iron) and fly ash (from burning coal). These materials leapfrog the most carbon-emitting, energy-intensive step in the cement production process.
The average global rate of clinker substitution could realistically reach 40 percent and avoid up to 440 million tons of carbon dioxide emissions annually. Standards and product scales will be key for realizing the opportunity of alternative cements.
