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