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  Geopolymer Concrete: from material synthesis mechanism to practical applications

The vast development of infrastructures has occasioned a pronounced increase in the ordinary Portland cement (OPC) consumption worldwide, which causes a heavy burden on the environment. Alkali-activated materials, termed as “geopolymers”, offer an environmentally-friendly toolkit of binders that can replace OPC in specific applications, due to their performance and durability advantages. Our research work is covering both fundamental theories and applied engineering within the context of two types of geopolymers: alkali-aluminosilicate (AAS) geopolymer and silico-aluminophosphate (SAP) geopolymer.

 

The full understanding of the fundamental theories of geopolymer binders is the first step to their commercialization. Our fundamental research is focusing on mixing method, rheology and thixotropy of geopolymer, and engineering properties. The mixing methodology profoundly affects the properties of the geopolymer binders, at which the “one-part” or “two-part” mixing terminologies are currently the primary production methods. On the one hand, understanding the rheological behavior in general and thixotropy in specific is a crucial step for the wide range application of such binders. On the other hand, the engineering properties of geopolymer binders, including mechanical performance and durability, are also of great importance to practical engineering. Thus, we combine experimental investigations and numerical modeling to explain the corresponding mechanisms the govern the behavior of geopolymer binders.    

 

In our group, we also focus on applied research, including the engineered geopolymer composites (EGC), digitalized geopolymer (3D printing), and production of artificial aggregate. The EGCs have great potential to be used as environmentally-friendly repair material due to their remarkable strain and deflection hardening behaviors. The production of a digitalized geopolymer follows the technology of either powder bed or extrusion-based 3D printing. By means of geopolymerization, solid waste can be fabricated as artificial aggregates to relieve the shortage of natural resources sustainably.

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Fig.2.1 Reaction steps and synthesis mechanisms of geopolymer binders
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Fig.2.2 Fundamental and applied research on geopolymer binders

Selected Publications

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  1.  Qian, L.P., Xu, L.Y., Alrefaei, Y.*, Wang, T., Ishida, T. and Dai, J.G*(2022), Artificial alkali-activated aggregates developed from wastes and by-products: A state-of-the-art review, Resources, Conservation and Recycling, 177, 105971. (DOI)

  2. Kumar, S., Chen, B., Xu, Y. and Dai, J.G.* (2022), Axial-flexural behavior of FRP grid-reinforced geopolymer concrete sandwich wall panels enabled with FRP connectors, Journal of Building Engineering, 47, 103907. (DOI)

  3. Huang, J.Q., S., Xu, Y., Huang, H. and Dai, J.G.* (2022), Structural behavior of FRP connector enabled precast geopolymer concrete sandwich panels subjected to one-side fire exposure, Fire Safety Journal, 128, 103524. (DOI)

  4. Xu, L.Y., Huang, B. T.*, Li, Victor C. and Dai, J.G.* (2022), High-strength high-ductility Engineered/Strain-Hardening Cementitious Composites (ECC/SHCC) incorporating geopolymer fine aggregates, Cement and Concrete Composites, 125, 104296.  (DOI)

  5. Kumar, S., Chen, B.Q., Xu, Y.Y. and Dai, J.G.* (2021), Structural Behavior of FRP Grid-Reinforced Geopolymer Concrete Sandwich Wall Panels Subjected to Concentric Axial Loading, Composite Structures, 114117,  (DOI)

  6. Wang, Y.S., Alrefaei, Y. and Dai, J.G.* (2021), Roles of hybrid activators in improving the early-age properties of one-part geopolymer pastes, Construction and Building Materials, 306, 124880. (DOI)

  7. Xu, L. Y., Huang, B.T.* and Dai, J.G.* (2021), Development of Engineered Cementitious Composites (ECC) Using Artificial Fine Aggregates, Construction and Building Materials, 305, 124742. (DOI)

  8. Kai, M.F. and Dai, J.G.*(2021), Understanding Geopolymer Binder-Aggregate Interfacial Characteristics at Molecular Level, Cement and Concrete Research, 149, 106582. (DOI)

  9. Xu, L.Y., Qian, L.P., Huang, B.T. and Dai, J.G.* (2021), Development of Artificial One-Part Geopolymer Lightweight Aggregates by Crushing Technique, Journal of Cleaner Production, 315, 128200. (DOI)

  10. Wang, Y.S., Peng, K.D., Alrefaei, Y. and Dai, J.G.* (2021), The Bond between Geopolymer Repair Mortars and OPC Concrete Substrate: Strength and Microscopic Interactions, Cement and Concrete Composites, 119, 103991. (DOI)

  11. Alrefaei, Y., Wang, Y.-S., Dai, J.-G*(2021), Effect of Mixing Method on the Performance of Alkali-activated Fly Ash/Slag Pastes along with Polycarboxylate Admixture, Cement and Concrete Composites, 117, 103917.  (DOI)

  12. Xu, L.Y., Alrefaei, Y., Wang, Y.-S., Dai, J.-G*(2021), Recent Advances in Molecular Dynamics Simulation of the N-A-S-H Geopolymer System: modeling, structural analysis and dynamics, Construction and Building Materials, 276: 122196. (DOI)

  13. Huang, J.-Q., Dai, J.G.* (2020). Flexural Performance of Precast Geopolymer Concrete Sandwich Panel Enabled by FRP Connector. Composite Structures. 248, 112563. (DOI)

  14. Qian, L.-P., Wang, Y.-S., Alrefaei, Y., Dai, J.-G*. (2020). Experimental study on full-volume fly ash geopolymer mortars: Sintered fly ash versus sand as fine aggregates.  Journal of Cleaner Production. 263, 121445. (DOI)

  15. Tang, N., Yang, K.-K., Alrefaei, Y., Dai, J.-G*., Wu, L.-M., Wang, Q. (2020). Reduce VOCs and PM emissions of warm-mix asphalt using geopolymer additives. Construction and Building Materials, 244, 118338. (DOI)

  16. Wang, Y.-S., Alrefaei, Y., Dai, J.-G*. (2020). Influence of coal fly ash on the early performance enhancement and formation mechanisms of silico-aluminophosphate geopolymer. Cement and Concrete Research, 127,105932. (DOI)

  17. Alrefaei, Y., Wang, Y. S., and Dai, J. G.* (2019). The effectiveness of different superplasticizers in ambient cured one-part alkali activated pastes. Cement and Concrete Composites, 97, 166-174. (DOI)

  18. Wang, Y. S., Alrefaei, Y., and Dai, J. G.* (2019). Silico-aluminophosphate and Alkali-aluminosilicate Geopolymers: A comparative review. Frontiers in Materials, 6, 106. (DOI)

  19. Wang, Y.S., Provis, John L.* and Dai, J.G.* (2018), Role of Soluble Aluminum Species in the Activating Solution for Synthesis of Silico-aluminophosphate Geopolymers, Cement and Concrete Composites, 93:186-195. (DOI)

  20. Xue, X., Liu, Y.L., Dai, J.G.*, Poon, C.S., Zhang, W.D. and Zhang, P. (2018), Inhibiting Efflorescence Formation on Fly Ash-based Geopolymer via Silane Surface Modification, Cement and Concrete Composites, 94: 42-52. (DOI)

  21. Alrefaei, Y. and Dai, J.G.*(2018), Tensile Behavior and Microstructure of Hybrid Fiber Ambient Cured One-part Engineered Geopolymer Composites, Construction and Building Materials, 184: 419-431. (DOI) 

  22. Ding Y., Dai, J.G.* and Shi, C.J. (2018), Fracture Property of Alkali-activated Slag and Ordinary Portland Cement Concrete, Construction and Building Materials, 165: 310-320. (DOI)

  23. Ding, Y., Dai, J.G.* and Shi, C.J. (2018), Mechanical Properties of Alkali-activated Concrete Subjected to Impact Load, ASCE, Journal of Materials in Civil Engineering, 30(5), 04018068. (DOI)

  24. Tang, N.*., Deng, Z., Dai, J.G., Yang, K., Chen, C., and Wang, Q. (2018), Geopolymer as an Additive of Warm Mix Asphalt: Preparation and properties, Journal of Cleaner Production, 192: 906-915. (DOI)

  25.  Shang, J., Dai, J.G., Zhao, T.J., Guo, S.Y.*, Zhang, P. and Mu, B. (2018), Alternation of Traditional Cement Mortars Using Fly Ash-Based Geopolymer Mortars Modified by Slag, Journal of Cleaner Production, 203: 745-756. (DOI)

  26.  Li, T., Zhang Y.M.* and Dai, J.G.* (2017), Flexural Behavior and Microstructure of Hybrid Basalt Textile and Steel Fiber Reinforced Alkali-activated Slag Panels Exposed to Elevated Temperatures, Construction and Building Materials, 152: 651-660. (DOI)

  27. Wang, Y.S., Dai, J.G.*, Ding, Z. and Xu, W.T. (2017), Phosphate-based Geopolymer: Formation mechanism and thermal stability, Materials Letters, 190: 209-212. (DOI)

  28. Ding, Y., Dai, J.G.* and Shi, C.J. (2016), Mechanical Properties of Alkali-Activated Concrete: A State-of-the-Art Review, Construction and Building Materials, 127(2016): 68-79. (DOI)

  29. Yang, L.Y., Jia, Z.J., Zhang, Y.M.* and Dai, J.G. (2015), Effects of Nano-TiO2 on Strength, Shrinkage and Microstructure of Alkali Activated Slag Paste, Cement & Concrete Composites, 57: 1-7. (DOI)

 

Selected Projects

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  • 2020/2021 Round, PI, Research and Development on Waste Ash/Slag-based Artificial Aggregates for Applications in Concrete, HK$1,154,954, Project Code: N_PolyU542/20.

  • NSFC 2016/2017 Round, Key Project, Co-PI, Fundamental Research on Materials and Structural Design of Green Low-Carbon Geopolymer Concrete, Allocated with CNY600,000 out of the total CNY3.0 million for five years, Project code: 51638008, PI: Prof Shi. C.J. (Hunan University).

  • ITF-Tier 3, 2017 Round, PI, Research and Development on Geopolymer Cement-based 3D Printing Technology for Modern Building Industry, HK$1,473,000, Project code: ITS/009/17.

  • ITF-Tier 3, 2012 Round, PI, Development of Thin Wall Panels Based on Basalt Textile Reinforced Geopolymer for Sustainable Building Construction, HK$986,700, Project code: ITS/064/12, Co-I: Prof. J.L. Hu (PolyU).

Dai Group on Sustainable
           Concrete Infrastructure
                         -Emerging Materials and Structural Systems

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