Mechanical Properties of Fly Ash and Blast Furnace Slag Based Geopolymer Mortars in Thermal Curing Environment

Öz

As a result of the clinker production of cement, CO2 emission, which harms the nature and causes global warming, occurs. For this reason, studies continue on the production of geopolymer mortar by using mineral additives instead of Portland cement in order to reduce CO2 emissions. In this study, 4M, 8M, 12M NaOH and Na2SiO3 (Sodium Silicate) were used as alkali activators. The ratio of Na2SiO3/NaOH was determined as 2 and kept constant in all experimental series. By producing blast furnace slag, fly ash and 50% hybrid geopolymer mortars from both, curing was carried out in the oven bag at 50 ℃, 75 ℃, 100 ℃ for 12 hours. In order to determine the mechanical properties of the samples after curing, tensile and compressive strength in bending and Scanning Electron Microscope (SEM) tests were carried out for microstructure analysis. According to the results obtained, the compressive strength for all samples provided the best performance at 100 ℃. The average bending tensile strength of the samples produced with 4M NaOH, Na2SiO3 and blast furnace slag was 5.4 MPa and the compressive strength was 60.05 MPa. It has been observed that the compressive and bending tensile strengths of the samples produced with fly ash are quite low compared to the blast furnace slag.

Anahtar Kelimeler

• Geopolymer
• blast furnace slag
• fly ash
• sodium silicate
• sodium hydroxide

Uçucu Kül ve Yüksek Fırın Cüruf Esaslı Geopolimer Harçların Isıl Kür Ortamında Mekanik Özellikleri

Öz

Çimentonun klinkeri üretimi sonucu, doğaya zarar veren ve küresel ısınmaya neden olan CO2 salınımı oluşmaktadır. Bu sebeple CO2 salınımını azaltmak için portland çimentosu yerine mineral katkı malzemeleri kullanılarak geopolimer harç üretimi üzerindeki çalışmalar devam etmektedir. Bu çalışmada alkali aktivatör olarak 4M, 8M, 12M NaOH ve Na2SiO3 (Sodyum Silikat) kullanılmıştır. Na2SiO3/NaOH oranı 2 olarak belirlenip bütün deney serilerinde sabit tutulmuştur. Yüksek fırın cürufu, uçucu kül ve her ikisinden %50 oranında hibrit geopolimer harçlar üretilerek 12 saat süresince fırın torbası içerisinde 50 ℃, 75℃, 100℃ etüvde kür uygulaması yapılmıştır. Kür uygulaması sonucunda mekanik özelliklerini belirlemek için numunelerin eğilmede çekme ve basınç dayanımı, mikroyapı analizleri için ise Taramalı Elektron Mikroskobu (SEM) deneyleri yapılmıştır. Elde edilen sonuçlara göre bütün numuneler için basınç dayanımı 100 ℃’de en iyi performansı sağlamıştır. 4M NaOH, Na2SiO3 ve yüksek fırın cürufu ile üretilen numunelerin ortalama eğilmede çekme dayanımı 5,4 MPa ve basınç dayanımı 60.05 MPa sonuçları elde edilmiştir. Uçucu kül ile üretilen numunelerde basınç ve eğilmede çekme dayanımları yüksek fırın cürufuna göre oldukça düşük olduğu görülmüştür.

Anahtar Kelimeler

• Geopolimer
• Yüksek Fırın Cürufu
• Uçucu Kül

Kaynakça

1. [1] N.B. Singh, B. Middendorf Geopolymers as an alternative to Portland cement: an overview Construct. Build. Mater. 237 (2020), Article 117455.
2. [2] I. Balczr, T. Korim, A. Dobrdi, Correlation of strength to apparent porosity of geopolymers Understanding through variations of setting time, Constr. Build. Mater. 93 (2015) 983–988.
3. [3] C. Un, J. Sanjayan, R. San Nicolas, J. van Deventer, Predictions of long-termdeflection of geopolymer concrete beams, Constr. Build. Mater. 94 (2015) 10–19.
4. [4] P.K. Sarker, R. Haque, K.V. Ramgolam, Fracture behaviour of heat cured fly ash based geopolymer concrete, Mater. Des. 44 (2013) 580–586.
5. [5] F. Okoye, J. Durgaprasad, N. Singh, Mechanical properties of alkali activated fly ash/Kaolin based geopolymer concrete, Constr. Build. Mater. 98 (2015) 685–691.
6. [6] B. Joseph, G. Mathew, Influence of aggregate content on the behavior of fly ash based geopolymer concrete, Sci. Iran. 19 (5) (2012) 1188–1194.
7. [7] L.K. Turner, F.G. Collins, Carbon dioxide equivalent (CO2-e) emissions: A comparison between geopolymer and OPC cement concrete, Constr. Build. Mater. 43 (2013) 125–130.
8. [8] C. Gunasekara, D.W. Law, S. Setunge, J.G. Sanjayan, Zeta potential, gel formation and compressive strength of low calcium fly ash geopolymers, Constr. Build. Mater. 95 (2015) 592–599.

9. [9] P. Nuaklong, K. Janprasit, P. Jongvivatsakul Enhancement of strengths of high-calcium fly ash geopolymer containing borax with rice husk ash J. Build. Eng. (2021), Article 102762.
10. [10] Lam, T. V., & Vu, K. D. Influence of NaOH-concentration and blast-furnace-slag on the properties of geopolymer mortars. Magazine of Civil Engineering, 115(7), (2022) 146–158.
11. [11] Huseien G.F., Mirza J., Ismail M., Hussin M.W. Influence of different curing temperatures and alkali activators on properties of GBFS geopolymer mortars containing fly ash and palm-oil fuel ash Construction and Building Materials, (2016) 125 , pp. 1229-1240.
12. [12] Tole I, Rajczakowska M, Humad A, Kothari A, Cwirzen A. Geopolymer Based on Mechanically Activated Air-cooled Blast Furnace Slag. Materials (Basel, Switzerland), (2020) 13(5).
13. [13] Inti, S., Sharma, M. & Tandon, V. Influence of Curing on the Properties of Geopolymer Mortar Made with Low Molarity Sodium Hydroxide. Transp. in Dev. Econ, (2017) 3, 11.
14. [14] Mohd Salahuddin, M.B.; Norkhairunnisa, M.; Mustapha, F. A review on thermophysical evaluation of alkali-activated geopolymers. Ceram. Int. 41, (2015) 4273–4281.
15. [15] J.L.Provis, Geopolymers and other alkali activated materials:why,how,and what? Mater Struct, 47(1-2)(2014) 11-25.
16. [16] Bakri, A.M.; Kamarudin, H.; Binhussain, M.; Nizar, I.K.; Rafiza, A.R.; Zarina, Y. Comparison of Geopolymer Fly Ash and Ordinary Portland Cement to the Strength of Concrete. Adv. Sci. Lett, 19, (2013) 3592–3595.
17. [17] Duxson, P.; Fernández-Jiménez, A.; Provis, J.L.; Lukey, G.C.; Palomo, A.; Van Deventer, J.S.J. Geopolymer technology: The current state of the art. J. Mater. Sci, 42, (2007) 2917–2933.
18. [18] Andini, S.; Cioffi, R.; Colangelo, F.; Grieco, T.; Montagnaro, F.; Santoro, L. Coal fly ash as raw material for the manufacture of geopolymer-based products. Waste Manag, 28, (2008) 416–423.
19. [19] Palomo, A., Alonso, S., Fernández-Jiménez, A., Sobrados, I., Sanz, J., Alkaline activation of fly ashes: a NMR study of the reaction products, Journal of American Ceramics Society, 87 (2004) 1141-1145.
20. [20] Pacheco-Torgal, F., Labrincha, J.A., Leonelli, C., Palomo, A., Chindaprasirt P., Handbook of Alkali-Activated Cements, Mortars and Concretes, Woodhead Publishing, Cambridge, UK, (2016) 852p.
21. [21] Coppola, L.; Bellezze, T.; Belli, A.; Bignozzi, M.C.; Bolzoni, F.; Brenna, A.; Cabrini, M.; Candamano, S.; Cappai, M.; Caputo, D.; et al. Binders alternative to Portland cement and waste management for sustainable construction—Part 1. J. Appl. Biomater. Funct. Mater 16, (2018) 186–202.
22. [22] Chindaprasirt, P. Challenge of Adopting Relatively Low Strength and Self-cured geopolymer for Road Construction Application: A Review and Primary Laboratory Study. Int. J. Pavement. Eng. (2019) 1–15.
23. [23] Yazıcı, N; Karagöl, F; Examination of Mechanical and Durability Properties of Fly Ash Based and Slag Added Geopolymer Concretes. Journal of the Institute of Science and Technology, 12(3), (2022) 1592 – 1606.
24. [24] Nasr, D., Pakshir, A. H., & Ghayour, H, (2018). The Influence of Curing Conditions and Alkaline Activator Concentration on Elevated Temperature Behavior of Alkali Activated Slag (AAS) Mortars. Construction and Building Materials 190, (2018) 108–119.
25. [25] Türker, P., Erdoğan, B., Katnaş, F. Ve Yeğınobalı, A., Uçucu küllerin sınıflandırılması ve özellikleri, Türkiye Çimento Müstahsilleri Birliği, Ankara, 2003.
26. [26] TS EN 196-7, "Çimento Deney Yöntemleri - Bölüm 7: Çimentodan Numune Alma ve Numune Hazırlama Yöntemleri", TSE, 2010.
27. [27] TS EN 196-1, 2016. Methods of testing cement - Part 1: Determination of strength, TSE-Turkey.
28. [28] Yaprak, H., & Kaplan, G., Farklı Kür Koşullarının Taban Külü Katkılı Geopolimerlerin Termal ve Mekanik Özelliklerine Etkisi. Tübav Bilim Dergisi, 9(3), (2016) 41-51.
29. [29] Ionescu BA, Chira M, Vermesan H, et al. Influence of Fe2O3, MgO and Molarity of NaOH Solution on the Mechanical Properties of Fly Ash-Based Geopolymers. MATERIALS. (2022) 15(19):6965.
30. [30] Yaprak H, Alnkaa A, Memis, et al. Effects of different curing conditions on the properties of geopolymeric mortar. MOJ Civil Eng. 5(1), (2019) 45-50.
31. [31] Yilmazoglu, A, Yildirim, ST, Behçet, ÖF, Yıldız, S. Performance evaluation of fly ash and ground granulated blast furnace slag-based geopolymer concrete: A comparative study. Structural Concrete. (2022) 23: 3898– 3915.
32. [32] Fernandez-Jimenez, A., Palomo, A., Composition and Microstructure of Alkali Activated Fly Ash Binder: Effect of the Activator, Cement and Concrete Research, 35, (2016) 1984-1992.
33. [33] Mo, B. H., Zhu, H., Cui, X. M., He, Y., & Gong, S. Y. Effect of curing temperature on geopolymerization of metakaolin-based geopolymers. Applied clay science, 99, (2014) 144-148.