Seawater as Alkali Activator in Fly Ash Based Geopolymer


  • Andrie Harmaji Institut Teknologi Sains Bandung



Seawater, Geopolymer, Alkali Activator, Anorthite


Indonesia as a maritime country in the world with 66% of its territory consists of maritime territory. A lot of potential that can be exploited, such as sea water. XRD characterization results indicate that the sea water from Tanjung Priok, North Jakarta, Indonesia has a compound Halite (NaCl) and Bassanite (CaSO4.5H2O) in the salt form. These compounds are alkaline thereby can influence the compressive strength of the geopolymer. Geopolymer is made up of aluminosilicate precursors which are activated by the alkaline activator solution, which usually combines sodium silicate and sodium hydroxide. The precursor material is waste from the coal based power plant called fly ash that produce 219.000 tonne per year and still underutilized but potentially as an alternative to cement. In this study, seawater was used to substitute the sodium hydroxide in alkali activator as an effort to reduce the manufacturing cost of Geopolymer. Geopolymer prepared by mixing fly ash as a precursor, silica sand as aggregates, with activator, then casted and cured by immersion. After 28 days compression test was conducted to measure the strength of resulting geopolymer. The sample consisted of a mixture of fly ash, silica sand, waterglass, and seawater produces strength of 16.60 MPa. X-Ray Diffraction characterization was conducted to study the compound formed from precursors activated with seawater alkali activator. Resulting diffractogram indicate the formation of anorthite compound as proof of Geopolymerization has been successfully occured.


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Author Biography

Andrie Harmaji, Institut Teknologi Sains Bandung

Department of Metallurgical Engineering


Alzaza, A., Ohenoja, K., Illikainen, M. (2022). Improved strength development and frost resistance of Portland cement ground-granulated blast furnace slag binary binder cured at 0 °C with the addition of calcium silicate hydrate seeds. Journal of Building Engineering, 48, 103904.

Bumanis G, Vitola L, Pundiene I, Sinka M, Bajare D. (2020). Gypsum, Geopolymers, and Starch—Alternative Binders for Bio-Based Building Materials: A Review and Life-Cycle Assessment. Sustainability, 12(14), 5666

Camerini, R., Poggi, G., Ridi, F., Baglioni, P. (2022). The kinetic of calcium silicate hydrate formation from silica and calcium hydroxide nanoparticles. Journal of Colloid and Interface Science, 605, 33-43.

Do, Q. M., Bui, T. H., & Nguyen, H. T. (2019). Effects of Seawater Content in Alkaline Activators to Engineering Properties of Fly Ash-Based Geopolymer Concrete. Solid State Phenomena, 296, 105–111.

Harmaji, A., dan Sunendar, B., (2016). Utilization of Fly Ash, Red Mud and Electric Arc Furnace Dust Slag for Geopolymer. Materials Science Forum, 841, 157-161.

He, W., Liu, C., Zhang, L. (2019). Effects of sodium chloride on the mechanical properties of slag composite matrix geopolymer. Advances in Cement Research, 31(9), 389-398.

Hernández-Bautista, E., S.Sandoval-Torresa, P.F. de J.Cano-Barritaa, Bentz, D.P. (2017). Modeling heat and moisture transport in steam-cured mortar: Application to AASHTO Type VI beams. Construction and Building Materials, 151, 186-195.

Huseien, G.F., Ismail, M., Khalid, N.H.A., Hussin, M.W., Mirza, J. (2018). Compressive strength and microstructure of assorted wastes incorporated geopolymer mortars: Effect of solution molarity. Alexandria Engineering Journal, 57(4), 3375-3386.

Jamil, N.H.; Abdullah, M..M.A.B.; Pa, F.C.; Mohamad, H.; Ibrahim,W.M.A.W.; Amonpattaratkit, P.; Gondro, J.; Sochacki,W.; Ibrahim, N. (2021). Self-Fluxing Mechanism in Geopolymerization for Low-Sintering Temperature of Ceramic. Materials, 14, 1325.

Jang, I., Son, D., Son, Y., Min, J., & Yi, C. (2021). Use of Methylcellulose-Based Pellet to Enhance the Bacterial Self-Healing of Cement Composite. Materials (Basel, Switzerland), 14(20), 6113.

Kirchheim, A. P., Rodríguez, E. D., Myers, R. J., A Gobbo, L., M Monteiro, P. J., C C Dal Molin, D., de Souza, R. B., & Cincotto, M. A. (2018). Effect of Gypsum on the Early Hydration of Cubic and Na-Doped Orthorhombic Tricalcium Aluminate. Materials (Basel, Switzerland), 11(4), 568.

Kunther, W., Ferreiro, S., Skibsted, J. (2017). Influence of the Ca/Si ratio on the compressive strength of cementitious calcium–silicate–hydrate binders. J. Mater. Chem. A, 5, 17401-17412.

Li, M., Lan, M., Chen, Z., Wang, J., Cui, S., & Wang, Y. (2020). Research on the Hydration Properties of C4A3S-CSH2 Cement System at Different Temperatures. Materials (Basel, Switzerland), 13(18), 4000.

Payá Bernabeu, J., Monzó, J., Borrachero, M. V., Soriano, L., & Tashima, M. M. (2022). Alternative activators in alkali activated cements. Revista ALCONPAT, 12(1), 16 - 31.

Pyatina, T., Sugama, T. (2020). Cements with supplementary cementitious materials for high-temperature geothermal wells. Geothermics. 86, 101840.

Rintala, A.; Havukainen, J.; Abdulkareem, M. (2021). Estimating the Cost-Competitiveness of Recycling-Based Geopolymer Concretes. Recycling, 6, 46.

Tavares, L.R.C., Junior, J.F.T., Costa, L.M. et al. (2020). Influence of quartz powder and silica fume on the performance of Portland cement. Sci Rep 10, 21461.

Torres-Carrasco, M., Puertas, F. (2017). Alkaline activation of different aluminosilicates as an alternative to Portland cement: Alkali activated cements or geopolymers. Revista Ingenieria de Construccion, 32(2), 5-12

Van Tran, M., Chau, V.N. (2021). Mass Concrete Placement of the Offshore Wind Turbine Foundation: A Statistical Approach to Optimize the Use of Fly Ash and Silica Fume. Int J Concr Struct Mater 15, 50.

Wong, B.Y.F., Wong, K.S., Phang, I.R.K. (2019). IOP Conf. Ser.: Mater. Sci. Eng, 495, 012070.

Zhu, S., Fang, Y., Guo, Y., Ma, X. (2019). Preparation of nano-calcium silicate hydrate and its application in concrete. IOP Conf. Ser.: Mater. Sci. Eng, 631, 022052.

Zunino, F., Scrinever, K. (2020). Factors influencing the sulfate balance in pure phase C3S/C3A systems. Cement and Concrete Research, 133, 106085.






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