Preparation and Characterization of Some Blended Cement Pastes

Abstract

Cement is commonly used in building and construction practices all over the world. Cement production emits a large amount of CO2 as a result of fuel burning and limestone decarbonation. For every 1000 kg of cement produced, 900 kg of CO2 is liberated. It is also responsible for 5% of greenhouse gas emissions. This investigation aims to prepare blended cement with a large amount of CKD and low OPC percentage by mixing 10% of OPC and 40,50,60% cement kiln dust (CKD) with various amounts of ground granulated blast furnace slag (GBFS), metakaolin (MK), and ground clay brick (GCB). Sulphate resistance was examined for all hardened cement pastes. Hydration characteristics of hardened cement pastes were investigated by determining compressive strength, combined water content, bulk density and porosity. XRD of some selected cement pastes was used to investigate the phase composition of hydrate formed. The result indicated that compressive strength, chemically combined water, and bulk density increase while porosity decrease with increasing hydration time. On the other hand, for pastes immersed in sulphate the compressive strength gradually increases till 90 days and then decreases as a result of gypsum and ettringite formation. CKD activates latent hydraulic properties of some pozzolanic material. Using GGBFS produces more strong hardened cement pastes than MK. This is mainly due to the higher pozzolanic activity of GGBFS. Using GCB gives the lowest compressive strength values because of lower pozzolanic activity of GCB.