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Realistic Ways to Drastically Reduce the CO2 Emission of Cement and Concrete
Farshad Rajabipour
Department of Civil and Environmental Engineering
Concrete is the #1 human-made materialAnnual world production:
~33 billion tons = 4.4 tons/person/year
1cm
(Ashby 2013)
Cement CO2 emissions = 2.3 GT/yr(~6% of total anthropogenic CO2 emissions)
CaCO CaO CO
Limestone, clay
1450oC
Source: PCA
• Cement chemistry uses most abundant elements on earth
• New cement plants operatenear thermodynamic efficiency
Only scalable, impactful, and rapidly implementable solution to curb CO2 emissions: Use less Portland cement
1. Replace cement with supplementary cementitious materials (SCM)
0 2 4 6 8 10 12 14 16
Silica fumeWaste glass
Biomass ashesNatural…
SlagFly ash
Portland cementLimestone
Calcined clay
GT/yr
LC3 reduces CO2 emissions of cement by up to 30% → ~85GT CO2 reduction over 30 years
0
1000
2000
3000
4000
5000
6000
0 10 20 30
Com
pres
sive
stre
ngth
(psi
)
Age (day)
Control LC3 SC3~ 30% carbon
< ~5% carbon
2. Improve (double) the service life of concrete structures (100+ years)
ASR damage Corrosion
Asset Management
New NY Bridge
Conclusions and AcknowledgementsOnly realistic way of drastically reducing the CO2 emission of concrete is to reduce the use of Portland cement:
• Replace 50% of cement with SCMs• Double the service life of concrete structures