Toughness and Volume Stability of Alkali-activated Fly Ash/Slag Geopolymers Modified with Isocyanate

Abstract

The effects of isocyanate (IA) incorporation on the toughness and volume stability of AAFS were systematically investigated. Various IA dosages were introduced into AAFS, and their influence on mechanical properties, microstructure, and shrinkage behavior was evaluated. The experimental results indicate that, with the incorporation of 5% IA, the 28-day compressive strength reaches 48.6 MPa, the 56-day drying shrinkage decreases by 35.91%, and minimal cracking is observed in the ring test. Microstructural analyses using SEM, XRD, and FTIR reveal that IA reacts with water to form urethane and biuret, which crosslinks into a durable network structure. This network fills pores, reducing internal stresses and improving both toughness and volume stability. These findings offer new insights into optimizing alkali-activated materials for construction applications and provide a potential pathway for the development of more durable and stable geopolymers.

Keywords

isocyanate / alkali-activated fly ash/slag / volume stability / toughness / microstructure

References

[1] Juenger MCG, Winnefeld F, Provis JL, et al. . Advances in Alternative Cementitious Binders. Cem. Concr. Res.. 2011, 41(12): 1 232-1 243 J]

[2] Shi C, Qu B, Provis JL. Recent Progress in Low-Carbon Binders. Cem. Concr. Res.. 2019, 122: 227-250 J]

[3] Alves BIA, Marvila MT, Linhares Júnior JAT, et al. . Alkaline Activation of Binders: A Comparative Study. Materials. 2024, 17(3): 667 J]

[4] Liu C, Wang X, Li Y, et al. . Evaluation on Preparation and Performance of a Low-Carbon Alkali-Activated Recycled Concrete under Different Cementitious Material Systems. Materials. 2024, 17(19): 4 869 J]

[5] Neupane K. Fly Ash and GGBFS Based Powder-Activated Geopolymer Binders: A Viable Sustainable Alternative of Portland Cement in Concrete Industry. Mech. Mater.. 2016, 103: 110-122 J]

[6] Wardhono A, Gunasekara C, Law DW, et al. . Comparison of Long Term Performance between Alkali Activated Slag and Fly Ash Geopolymer Concretes. Constr. Build. Mater.. 2017, 143: 272-279 J]

[7] Wang X, Kong L, Zhao W, et al. . Chloride Transport Resistance of Alkali-Activated Concrete Exposed to Combined Chloride, Sulfate and Carbonation Environment. Constr. Build. Mater.. 2023, 367: 130 353 J]

[8] Chi M, Huang R. Binding Mechanism and Properties of Alkali-Activated Fly Ash/Slag Mortars. Constr. Build. Mater.. 2013, 40: 291-298 J]

[9] Hu X, Shi C, Shi Z, et al. . Compressive Strength, Pore Structure and Chloride Transport Properties of Alkali-Activated Slag/Fly Ash Mortars. Cem. Concr. Compos.. 2019, 104: 103 392 J]

[10] Shah SFA, Chen B, Oderji SY, et al. . Improvement of Early Strength of Fly Ash-Slag Based One-Part Alkali Activated Mortar. Constr. Build. Mater.. 2020, 246: 118 533 J]

[11] Ye H, Radlińska A. Shrinkage Mechanisms of Alkali-Activated Slag. Cem. Concr. Res.. 2016, 88: 126-135 J]

[12] Huang D, Chen P, Peng H, et al. . A Review and Comparison Study on Drying Shrinkage Prediction Between Alkali-Activated Fly Ash/Slag and Ordinary Portland Cement. Constr. Build. Mater.. 2021, 305: 124 760 J]

[13] Fang G, Zhang M. Multiscale Micromechanical Analysis of Alkali-Activated Fly Ash-Slag Paste. Cem. Concr. Res.. 2020, 135: 106 141 J]

[14] Archez J, Farges R, Gharbi A, et al. . Influence of the Geopolymer Formulation on the Endogeneous Shrinkage. Constr. Build. Mater.. 2021, 298: 123 813 J]

[15] Amran M, Onaizi AM, Makul N, et al. . Shrinkage Mitigation in Alkali-Activated Composites: A Comprehensive Insight into the Potential Applications for Sustainable Construction. Results Eng.. 2023, 20: 101 452 J]

[16] Feng H, Bilal I, Sun Z, et al. . Mechanical and Shrinkage Properties of Cellulose Nanocrystal Modified Alkali-Activated Fly Ash/Slag Pastes. Cem. Concr. Compos.. 2024, 154: 105 753 J]

[17] Wang S, Ma X, He L, et al. . High Strength Inorganic-Organic Polymer Composites (IOPC) Manufactured by Mold Pressing of Geopolymers. Constr. Build. Mater.. 2019, 198: 501-511 J]

[18] Ferone C, Roviello G, Colangelo F, et al. . Novel Hybrid Organic-Geopolymer Materials. Appl. Clay Sci.. 2013, 73: 42-50 J]

[19] Mi J, Luo Z, Liu X, et al. . For the Improvement of Toughness and Volume Stability of Alkali-Activated Slag with Styrene-Acrylic Emulsion. J. Build. Eng.. 2022, 58: 105 040 J]

[20] Li F, Chen Q, Lu Y, et al. . Dry Shrinkage and Micro-Structure of Alkali-Activated Fly Ash/Slag Pastes Incorporated with Silane Coupling Agent Modified MWCNTs. Cem. Concr. Res.. 2024, 175: 107 382 J]

[21] Zhang A. Effect of Epoxy Resin on Mechanical Properties of Metakaolin Based Geopolymer and Microscopic Analysis. J. Wuhan Univ. Technol.-Mater. Sci. Ed.. 2020, 35(2): 431-434 J]

[22] Xing X, Xu W, Zhang G, et al. . The Mechanical Performance and Reaction Mechanism of Slag-Based Organic-Inorganic Composite Geopolymers. Materials. 2024, 17(3): 734 J]

[23] Chen X, Zhu G, Zhou M, et al. . Effect of Organic Polymers on the Properties of Slag-Based Geopolymers. Constr. Build. Mater.. 2018, 167: 216-224 J]

[24] Lu C, Wang Q, Liu Y, et al. . Influence of New Organic Alkali Activators on Microstructure and Strength of Fly Ash Geopolymer. Ceram. Int.. 2022, 48(9): 12 442-12 449 J]

[25] Wang M, Wang R, Zheng S, et al. . Research on the Chemical Mechanism in the Polyacrylate Latex Modified Cement System. Cem. Concr. Res.. 2015, 76: 62-69 J]

[26] Bizet B, Grau É, Carmail H, et al. . Water-Based Non-Isocyanate Polyurethane-Ureas (NIPUUs). Polym. Chem.. 2020, 11(23): 3 786-3 799 J]

[27] Delebecq E, Pascault JP, Boutevin B, et al. . On the Versatility of Urethane/Urea Bonds: Reversibility, Blocked Isocyanate, and Non-Isocyanate Polyurethane. Chem. Rev.. 2013, 113(1): 80-118 J]

[28] Arnold RG, Nelson JA, Verbanc JJ. Recent Advances in Isocyanate Chemistry. Chem. Rev.. 1957, 57(1): 47-76 J]

[29] Wang SD, Scrivener KL, Pratt PL. Factors Affecting the Strength of Alkali-Activated Slag. Cem. Concr. Res.. 1994, 24(6): 1 033-1 043 J]

[30] Duxson P, Fernández-Jiménez A, Provis JL, et al. . Geopolymer Technology: The Current State of the Art. J. Mater. Sci.. 2007, 42(9): 2 917-2 933 J]

[31] Criado M, Fernández-Jiménez A, Palomo A, et al. . Effect of the Na₂O Ratio on the Alkali Activation of Fly Ash. Part II: ²Si MAS-NMR Survey. Microporous Mesoporous Mater.. 2008, 109(1): 525-534 J]

[32] Luukkonen T, Sreenivasan H, Abdollahnejad Z, et al. . Influence of Sodium Silicate Powder Silica Modulus for Mechanical and Chemical Properties of Dry-Mix Alkali-Activated Slag Mortar. Constr. Build. Mater.. 2020, 233: 117 354 J]

[33] Chi M, Liu YC, Huang R. Effect of Alkali-Activators on the Setting Time and Compressive Strength for Alkali-Activated Fly Ash Mortars. Proc. 3rd Int. Conf. Microstruct. Prop. Cem. Based Mater.. 2013809-812[C]

[34] Sun Z, Vollpracht A. Isothermal Calorimetry and in-situ XRD Study of the NaOH Activated Fly Ash, Metakaolin and Slag. Cem. Concr. Res.. 2018, 103: 110-122 J]

[35] Taghvayi H, Behfarnia K, Khalili M. The Effect of Alkali Concentration and Sodium Silicate Modulus on the Properties of Alkali-Activated Slag Concrete. J. Adv. Concr. Technol.. 2018, 16(7): 293-305 J]

[36] Xu Z, Yue J, Pang G, et al. . Influence of the Activator Concentration and Solid/Liquid Ratio on the Strength and Shrinkage Characteristics of Alkali-Activated Slag Geopolymer Pastes. Adv. Civ. Eng.. 2021, 2021: 6 631 316 J]

[37] Alnahhal MF, Kim T, Hajimohammadi A. Distinctive Rheological and Temporal Viscoelastic Behaviour of Alkali-Activated Fly Ash/Slag Pastes: A Comparative Study with Cement Paste. Cem. Concr. Res.. 2021, 144: 106 441 J]

[38] Meador MAB, Capadona LA, McCorkle L, et al. . Structure-Property Relationships in Porous 3D Nanostructures as a Function of Preparation Conditions: Isocyanate Cross-Linked Silica Aerogels. Chem. Mater.. 2007, 19(9): 2 247-2 260 J]

[39] Chen Q, Zhu L, Huang L, et al. . Fracture of the Physically Cross-Linked First Network in Hybrid Double Network Hydrogels. Macromolecules. 2014, 47(6): 2 140-2 148 J]

[40] Hojati M, Radlińska A. Shrinkage and Strength Development of Alkali-Activated Fly Ash-Slag Binary Cements. Constr. Build. Mater.. 2017, 150: 808-816 J]

[41] Fang G, Bahrami H, Zhang M. Mechanisms of Autogenous Shrinkage of Alkali-Activated Fly Ash-Slag Pastes Cured at Ambient Temperature Within 24 h. Constr. Build. Mater.. 2018, 171: 377-387 J]

[42] Studer M, Peters K, Botsis J. Method for Determination of Crack Bridging Parameters Using Long Optical Fiber Bragg Grating Sensors. Compos. Part B-Eng.. 2003, 34(4): 347-359 J]

[43] Wang YR, Cao YB, Zhang ZH, et al. . Intrinsic Sulfuric Acid Resistance of C-(N)-A-S-H and N-A-S-H Gels Produced by Alkali-Activation of Synthetic Calcium Aluminosilicate Precursors. Cem. Concr. Res.. 2023, 165: 107 068 J]

[44] Leventis N, Sotiriou-Leventis C, Chandrasekaran N, et al. . Multifunctional Polyurea Aerogels from Isocyanates and Water. A Structure-Property Case Study. Chem. Mater.. 2010, 22(24): 6 692-6 710 J]

[45] Song QF, Guo MZ, Ling TC. A Review of Elevated-Temperature Properties of Alternative Binders: Supplementary Cementitious Materials and Alkali-Activated Materials. Constr. Build. Mater.. 2022, 341: 127 894 J]

[46] Xing X, Wei J, Xu W, et al. . Effect of Organic Polymers on Mechanical Property and Toughening Mechanism of Slag Geopolymer Matrix. Polymers. 2022, 14(19): 4 214 J]

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