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Advances in Concrete Construction Volume 10, Number 5, November 2020 , pages 403-416 DOI: https://doi.org/10.12989/acc.2020.10.5.403 |
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Effect of alkaline activators on the fresh properties and strength of silico-manganese fume-slag activated mortar |
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Muhammad Nasir, Megat Azmi Megat Johari, Moruf Olalekan Yusuf, Mohammed Maslehuddin and Mamdouh A. Al-Harthi
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| Abstract | ||
| This study investigated the effect of alkaline activators - NaOHaq (NH) (NH: 0-16 M) and Na2SiO3aq (NS) (NS/NH: 0-3.5) in the synthesis of silico-manganese fume (SMF) and ground blast furnace slag (BFS) blended alkali-activated mortar (AASB). The use of individual activator was ineffective in producing AASB of sufficient fresh and hardened properties, compared to the synergy of both activators. This may be attributed to incomplete dissolution and condensation of oligomers required for gelation of the binder. An inverse relationship was noted among the fresh properties and the NH concentration or NS/NH ratio. This was influenced by the dissolution and condensation of silicate monomers under polymerization process. The maximum 28-day strength of ~45 MPa, setting time of 60 min and flow of 182 mm was obtained with the use of combined activators (10M-NH and NS/NH=2.5). The combined activators at NS/10M-NH=2.5 constituted SiO2/Na2O, H2O/Na2O and H2O/SiO2 molar ratio of 1.61, 17.33 and 10.77, respectively. This facilitated the formation of C-S-H, C/K-A-S-H and C-Mn-S-H in the framework together with an increase in the crystallinity due to more silicate re-organization within the aluminosilicate chain. On comparison of the high concentrated with mild alkali synthesized product, it revealed that the concentration of OHand Si monomers together with alkali metals influenced the dissolution of precursors and embedment of the constituent elements in the polymeric matrix. These factors eventually contributed to the microstructural densification of the mortar prepared with NS/10M-NH=2.5 thereby enhancing the compressive strength. | ||
| Key Words | ||
| alkali concentration; activator dosage; molar composition; silico-manganese fume; blast furnace slag; strength; microstructure | ||
| Address | ||
| Muhammad Nasir: Department of Civil and Construction Engineering, College of Engineering, Imam Abdulrahman Bin Faisal University, Dammam 31451, Saudi Arabia Megat Azmi Megat Johari: School of Civil Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang, Malaysia Moruf Olalekan Yusuf: Department of Civil Engineering, University of Hafr Al Batin, Hafr Al Batin 31991, Saudi Arabia Mohammed Maslehuddin: Center for Engineering Research, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia Mamdouh A. Al-Harthi: Department of Chemical Engineering, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia; Center of Research Excellences in Nanotechnology, Research Institute, King Fahd University of Petroleum and Minerals, Dhahran 31261, Saudi Arabia | ||
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