Influence of Carbonation on Mechanical and Transport Properties of Limestone Calcined Clay Blend Mortar Mix

When calcium bearing phases of hydration products react with carbon dioxide, it results in formation of calcium carbonate. The consumption of alkaline compounds leads to reduction in the pH of concrete, thereby affecting the stability of hydration product and increasing the risk of steel corrosion in low alkaline environment. The reaction of pozzolans with calcium hydroxide reduces the reserve alkalinity in the hydrated cement paste which accelerates the rate of carbonation. The main objective is to determine the change in mechanical and transport properties of carbonated and non-carbonated samples. In this investigation, a cement blend mix has been prepared using OPC and limestone calcined clay. Mortar specimens were prepared for using blend to sand ratio as 1:3 to prepare samples for testing compressive strength, sorptivity and porosity using boiling water test. Paste samples were cast to measure reserve alkalinity and carry out thermogravimetric analysis. Some specimens were kept in carbonation chamber for 90 days at 3% CO₂ concentration and 60% relative humidity for carbonation to occur at an accelerated rate while the other samples were sealed to avoid carbonation. The results show that after carbonation, there is slight decrease in the compressive strength and increase in sorptivity after carbonation of LC³.