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Advances in Concrete Construction Volume 13, Number 1, January 2022 , pages 71-81 DOI: https://doi.org/10.12989/acc.2022.13.1.071 |
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Reactivity of aluminosilicate materials and synthesis of geopolymer mortar under ambient and hot curing condition |
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Idrees Zafar, Muhammad Akram Tahir, Rizwan Hameed, Khuram Rashid and Minkwan Ju
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| Abstract | ||
| Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100oC. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20oC, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions. | ||
| Key Words | ||
| characterization; fresh and hardened properties; geopolymer synthesis; parameters influencing reactivity | ||
| Address | ||
| Idrees Zafar: Department of Civil Engineering, College of Engineering, Imam Mohammad Ibn Saud Islamic University, P. O. Box 5701, Riyadh 11432, Saudi Arabia Muhammad Akram Tahir: Faculty of Engineering, University of Central Punjab, Lahore, Pakistan Rizwan Hameed: Department of Architectural Engineering and Design, University of Engineering and Technology, Main GT Road, 54890-Lahore, Pakistan Khuram Rashid: Department of Architectural Engineering and Design, University of Engineering and Technology, Main GT Road, 54890-Lahore, Pakistan Minkwan Ju: Department of Civil and Environmental Engineering, Yonsei University, 03722 Seoul, Republic of Korea | ||
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