Effect of calcium oxide on mechanical properties and microstructure of phosphoric acid-activated geopolymers
Source abstract
Abstract
Long curing time under normal temperature conditions and poor flowability are one of the main obstacles affecting the engineering application of phosphate acid-activated geopolymers. To improve the application potential of acid-activated geopolymers and evaluate their feasibility for use in high-level radioactive waste repositories, calcium oxide was used as partial substitute for precursor metakaolin to prepare the phosphoric acid-activated geopolymers (SAP). The workability, physical properties, and mechanical properties of the SAP with calcium oxide contents ranging from 3% to 15 by weight (wt.%) were studied. Moreover, the control SAP sample without calcium oxide was prepared as reference. The results showed that the SAP with calcium oxide exhibited a significant improvement in the workability and mechanical properties. Relative to the control sample (without calcium oxide), the optimal sample demonstrated significantly improved performance: the final setting time was shortened by 15.6 times, while the compressive strength increased by 3.6 times. Due to the introduction of calcium oxide, the water absorption and the apparent porosity of the SAP were decreased by 5.0%～14.6% and 5.1～30.1%, respectively. Additionally, the effect of calcium oxide on the hydration and microstructure of the geopolymers was evaluated using isothermal calorimeter, X-ray diffraction (XRD), thermal analysis (TG-DSC), Fourier infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). As a result, the addition of calcium oxide accelerated the polymerization reaction of the geopolymers and led to the formation of calcium phosphate salt crystals. SEM and EDS analyses revealed that calcium phosphate salt crystals distributed into silicate phosphate (S-P), aluminum phosphate (A-P), and aluminum silicate phosphate (S-A-P) gels, resulting in an increase in the compressive strength of the geopolymers.
Source: openalex_inverted_index · Quality: baseline
Research context
OpenAlex topics: Concrete and Cement Materials Research · Magnesium Oxide Properties and Applications · Microbial Applications in Construction Materials
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (60)
Show source-provided references
1. The Beishan underground research laboratory for geological disposal of high-level radioactive waste in China: Planning, site selection, site haracterization and in situ tests
2. Properties and reaction mechanism of phosphoric acid activated metakaolin geopolymer at varied curing temperatures10.1016/j.cemconres.2021.106425 ↗
3. Mechanochemically activated, durable, corrosion protective, advanced geopolymer material, containing gamma-Al2O3 and zinc phosphate
4. Structural study of the effect of nano additives on the thermal properties of metakaolin phosphate geopolymer by MASNMR, XPS and SEM analysis
5. Fire resistance of phosphoric acid-based geopolymer foams fabricated from metakaolin and hydrogen peroxide10.1016/j.matlet.2019.127228 ↗
6. Structural, thermal and dielectric properties of phosphoric acid-based geopolymers with different amounts of H3PO410.1016/j.matlet.2013.10.075 ↗
7. The phase evolution of phosphoric acid-based geopolymers at elevated temperatures10.1016/j.matlet.2011.08.043 ↗
8. Influence of various metakaolin raw materials on the water and fire resistance of geopolymers prepared in phosphoric acid10.1016/j.jnoncrysol.2018.09.005 ↗
9. Geopolymer local network evolution under time and temperature
10. Chemical deformation of metakaolin based geopolymer10.1016/j.cemconres.2019.03.017 ↗
11. Developing alkali-activated controlled low-strength material (CLSM) using urban waste glass and red mud for sustainable construction
12. Toward waste glass upcycling: Preparation and characterization of high-volume waste glass geopolymer composites
13. Investigation on the behavior of fly ash phosphate-based geopolymer stabilized acidic lead contaminated soil10.1016/j.jece.2024.114739 ↗
14. Influence of coal fly ash on the early performance enhancement and formation mechanisms of silico-aluminophosphate geopolymer10.1016/j.cemconres.2019.105932 ↗
15. A comparative study on geopolymers synthesized by different classes of fly ash after exposure to elevated temperatures
16. Synergistic mechanisms of magnesium slag on the reaction behavior of alkali-activated blast furnace slag10.1016/j.cemconcomp.2025.106434 ↗
17. Workability and mechanical performance of shield muck-slag-based engineered geopolymer composites modified with chemical admixtures
18. Geopolymers as an alternative to Portland cement: an overview10.1016/j.conbuildmat.2019.117455 ↗
19. An overview of geopolymers derived from industrial by-products10.1016/j.conbuildmat.2016.09.136 ↗
20. Mechanism of geopolymerization and factors influencing its development: a review10.1007/s10853-006-0401-4 ↗
21. A comprehensive review on compressive strength and microstructure properties of GGBS-based geopolymer binder systems10.1016/j.conbuildmat.2024.135242 ↗
22. A eco-friendly acid fly ash geopolymer with a higher strenght10.1016/j.conbuildmat.2022.127450 ↗
23. A green phosphate-based geopolymer adsorbent or binder with high specific surface area for environmental applications10.1016/j.conbuildmat.2023.133738 ↗
24. Silico-aluminophosphate and alkali-aluminosilicate geopolymers: a comparative review10.3389/fmats.2019.00106 ↗
25. Wang · 2018
26. Analytical investigation of phase assemblages of alkali-activated materials in CaO-SiO2-Al2O3 systems: The management of reaction products and designing of precursors10.1016/j.matdes.2020.108975 ↗
27. Investigation of phosphate based geopolymers formation mechanism
28. Mechanical and microstructural properties of metakaolin-based geopolymer cements from sodium waterglass and phosphoric acid solution as hardeners: a comparative study10.1016/j.clay.2017.02.002 ↗
29. A novel aluminosilicate geopolymer material with low dielectric loss10.1016/j.matchemphys.2011.06.039 ↗
30. Microstructural evidence of reconstituted limestone blocks in the great pyramids of Egypt
31. Phosphate-based geopolymer: formation mechanism and thermal stability10.1016/j.matlet.2017.01.022 ↗
32. Realization of high-percentage addition of fly ash in the materials for the preparation of geopolymer derived from acid-activated metakaolin10.1016/j.jclepro.2020.125430 ↗
33. Dicalcium phosphate cements: Brushite and monetite10.1016/j.actbio.2011.08.005 ↗
34. Comparative analysis of hydroxyapatite synthesized by sol-gel, ultrasonication and microwave assisted technique10.1016/j.matpr.2015.11.073 ↗
35. Influence of gibbsite and quartz in kaolin on the properties of metakaolin-based geopolymer cements10.1016/j.clay.2015.01.023 ↗
36. Ahin · 2012
37. Interface microstructure and compressive behavior of fly ash/phosphate geopolymer hollow sphere structures10.1016/j.matdes.2014.09.063 ↗
38. Role of soluble aluminum species in the activating solution for synthesis of silico-aluminophosphate geopolymers10.1016/j.cemconcomp.2018.07.011 ↗
39. Structural and dielectric comparative studies of geopolymers prepared with metakaolin and Tunisian natural clay10.1016/j.clay.2017.01.018 ↗
40. Preparation and Structural Characterization of Al2O3-nSiO2-mH3PO4 Phosphoric Acid- based Geopolymer
41. L. Zhang. Preparation of phosphoric acid-based porous geopolymers10.1016/j.clay.2010.10.004 ↗
42. Calcium phosphate cements for bone substitution: chemistry, handling and mechanical properties10.1016/j.actbio.2013.11.001 ↗
43. Improvement of early-age properties of silico-aluminophosphate geopolymer using dead burnt magnesia10.1016/j.conbuildmat.2019.05.050 ↗
44. Quantitative study of the reactivity of fly ash in geopolymerization by FTIR
45. The effects of synthesized calcium phosphate compounds on the mechanical and microstructural properties of metakaolin-based geopolymer cements10.1016/j.conbuildmat.2017.12.162 ↗
46. Surface decoration of polyimide fiber with carbon nanotubes and its application for mechanical enhancement of10.1016/j.apsusc.2017.04.166 ↗
47. Realization of high-percentage addition of fly ash in the materials for the preparation of geopolymer derived from acid-activated metakaolin10.1016/j.jclepro.2020.125430 ↗
48. Novel acid-based geopolymer synthesized from nanosized tubular halloysite: the role of precalcination temperature and phosphoric acid concentration10.1016/j.cemconcomp.2020.103601 ↗
49. Acid-based geopolymers: understanding of the structural evolutions during consolidation and after thermal treatments10.1016/j.jnoncrysol.2019.02.025 ↗
50. Infrared spectroscopy of sol-gel derived silica-based films: a spectra-microstructure overview10.1016/S0022-3093(02)01637-X ↗
51. Hydroxylation and dealumination of a metakaolinite-rich brick under acid conditions, and their influences on metal adsorption: one- and two-dimensional (1H, 27Al, 23Na, 29Si) MAS NMR, and FTIR studies10.1016/j.micromeso.2016.02.028 ↗
52. Geopolymers based on phosphoric acid and illito-Kaolinitic clay10.1155/2016/2359759 ↗
53. Compositional dependence of infrared absorption spectra studies for TeO2-P2O5 and TeO2-P2O5-Bi2O3 glasses10.1007/BF00696292 ↗
54. Quantitative study of the reactivity of fly ash in geopolymerization by FTIR
55. Water resistance and thermal behavior of metakaolin-phosphate-based geopolymer cements10.1080/21870764.2018.1507660 ↗
56. Synthesis and structure characterization of geopolymeric material based on metakaolinite and phosphoric acid
57. Kinetics of the conversion of monetite to calcium pyrophosphate10.1021/j100575a017 ↗
58. Influence of waste glass powder on the physico-mechanical properties and microstructures of fly ash-based geopolymer paste after exposure to high temperatures10.1016/j.conbuildmat.2020.120579 ↗
59. A laboratory investigation of steel to fly ash-based geopolymer paste bonding behavior after exposure to elevated temperatures10.1016/j.conbuildmat.2020.119267 ↗
60. Phosphate-based geopolymers: a critical review10.1007/s00289-021-03829-0 ↗