Physico-mechanical properties of lime-silica fume pastes modified with nano-metakaolin

The improvement in the physico-mechanical properties of lime-silica fume (SF) pastes through the incorporation of nano-metakaolin (NMK) was investigated. Lime-SF paste (1 : 1 by weight) was prepared as a reference binder. To examine the influence of NMK on strength development, SF was replaced with 2-10 wt% NMK. The compressive strength, capillary water absorption and pore structure of the designed mixes were determined after 3, 7 and 28 d of curing. X-ray diffraction analysis and differential scanning calorimetry were used to study the phase composition and scanning electron microscopy (SEM) was used for microstructural investigations. The lime-SF binder modified with 6% NMK exhibited the best mechanical performance. Pore structure analysis confirmed that NMK provided significant refinement in the pore structure of the blended pastes and SEM micrographs revealed noticeable microstructural improvements. The capillary water absorption coefficient decreased considerably with an increase in NMK content up to 6% compared with the reference mixture. Use of the developed lime-SF-NMK paste is recommended as a promising innovative binder for specific cement applications such as plastering and renovation of buildings.