Hydration Characteristics of Blended Cement Containing Metakaolin

Document Type : Original research papers


1 Tabbin Institute for Metallurgical Studies, Helwan, Cairo, Egypt.

2 Central Metallurgical R&D Institute, Helwan, Cairo, Egypt.

3 Faculty of Science, Ain Shams University, Cairo, Egypt.

4 Faculty of Engineering, Al-Azhar University, Cairo, Egypt.


Meta-kaolin as a pozzolanic active material was prepared by firing kaolin ore at different temperatures ranged from 500-1000°C for different soaking times from 1- 5 hours. Optimization of the preparation study was carried out. The optimum conditions were shown to be at 750°C for 5 hours. Mechanical and physico-chemical characterization of blended cement pastes made by partial replacement of Portland cement (PC) with 0, 5, 10 and 15 wt. % of metakaolin were studied. The pastes were hydrated for various time intervals of 1, 3, 7, 14 and 28 days. At each time interval, the hydrated pastes specimens were tested for compressive strengths, hydration kinetics, differential scanning calorimetry, XRD analysis and scanning electron microscopy. Blended pastes made of 90% OPC + 10% MK showed the highest compressive strength values at all hydration ages. DSC thermograms and XRD diffractograms results showed the formation of nearly amorphous calcium silicate hydrates (mainly as CSH. I & II), calcium sulphoaluminate hydrates (ettringite and monosulphate hydrates), calcium aluminate hydrates, calcium hydroxide (CH) and CaCOR3R. Scanning electron microscopy micrographs indicated the formation of denser microstructure for the hardened OPC- MK pastes as compared to neat OPC pastes after 28 days.


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