Ordinary Portland Cement (OPC) is by mass the largest manufactured
product on Earth, responsible for approximately 6% - 8% of global anthropogenic
carbon dioxide emissions (CO2) and 35% of industrial CO2 emissions. On average 0.8 to 0.9 ton of CO2 is emitted to produce
one ton of OPC. In this paper, partial substitution of clinker (30% - 35%) by
the calcined clay-limestone
mixture was investigated in order to produce an eco-cement (LC3). Analyzes by XRF, XRD and ATG/ATD have characterized
different components, determined the
calcination temperature and selected the right clay which can act as effective Supplementary Cementitious
Material (SCM). Mechanical tests on mortar carried out over a period of
90 days. The WBCSD/WRI “Greenhouse
Gas Protocol” methodology then allowed the calculation of CO2 emissions into the
atmosphere. Three types of clay are available in the Songololo Region. The
kaolinite is the principal clay mineral and its content varies from 27% to 34%.
The sum of kaolinite and amorphous phase which enable clay to react with
cementitious material ranges from 57% to 60%. The SiO2 content ranges from 33% to 76%, the
Alumina content from 12% to 20% so that the ratio Al2O3/SiO2 is on the higher side (0.17 - 0.53). The calcination window is between 750°C
and 850°C and the best clay which can act as SCM identified. The clinker’s
substitution reduced CO2 emissions from 0.824 ton of CO2 for one ton of OPC to 0.640 ton of CO2 for one ton of LC3, means 22%
less emissions. The compressive strengths
developed by LC3 vary from 8.91 to 57.6 MPa (Day 1 to Day 90), exceed
those of references 32.5 cement and are close to 42.5 cement. In view of the
results, LC3 cement can be considered for industrial trials.
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