Realistic Ways to Drastically Reduce the CO2 Emission of

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