Preliminary Results on Corrosion Rate in Carbonated LC³ Concrete

The new blended cement, LC³, can reduce by up to a 30% of the CO₂ emissions per ton of cement, including calcined clay and limestone as main components. However, the low level of clinker content concern about carbonation-induced corrosion of the reinforcing steel. The aim of this project is to measure the corrosion rate and understand the corrosion mechanism of reinforcing steel in concrete made with LC³ cement. The samples were cast in molds specifically designs in order to minimize the carbonation time and the moisture equilibration time. There is a finer porosity for LC³ cement and the porosity decrease when the carbonation takes place due to the transformation of the portlandite into calcite. However, when the clinker substitution is higher, the total porosity increase, but there is a coarsening porosity for blended systems after carbonation because the C-S-H are converted into calcite with a smaller volume. In all LC³ samples, the corrosion rate is higher compared with OPC cement, but there are differences regarding the induced carbonation and natural carbonation especially for LC³ samples with a more tortuous pore system than OPC assuring the high resistance to the carbonation.