Orthogonal analysis and mechanism of compressive strength and microstructure of the metakaolin-fly ash geopolymer

Yuan, Long; Ma, Yong; Zhang, Jian; Men, Jiahui; Sun, Tao; Zhao, Hongche; Wu, Hao; Wang, Hongguang; Dai, Shoushuai

doi:10.1016/j.cscm.2022.e01154

Cited by 7 publications

(5 citation statements)

References 51 publications

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“…The RCKC’s higher reactivity enables ample interaction to occur to sufficiently increase the degree of geopolymerization. It was reported [ 42 ] in the pure metakaolin system after the geopolymerization process was completed that the lamellar structure of kaolinite undergoes disintegration and is transformed into dense gel formation. However, the simultaneous mixing of aluminosilicates particles in Mix 2 results in an incomplete reaction and dissolution of kaolinite.…”

Section: Resultsmentioning

confidence: 99%

Influence of Mixing Order on the Synthesis of Geopolymer Concrete

et al. 2022

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Geopolymers are high-performance, cost-effective materials made from industrial waste that ideally fit the needs of 3D printing technology used in construction. The novelty of the present work lies in the investigation of methods to mix geopolymer concrete from fly ash (FA) class F, ground granulated blast furnace slag (GGBS), and raw calcined kaolin clay (RCKC) to determine the mixing procedure which provides the best mechanical strength and structural integrity. The experimental results show that aluminosilicates with different reaction parameters when mixed one after another provide the optimal results while the geopolymer concrete possesses the highest compressive strength and the denser structure. The results demonstrated that the reactivity of GGBS, FA, and RCKC increased for different depolymerization speeds of the selected aluminosilicates. This research will provide results on how to improve the mixing order for geopolymer synthesis for 3D printing demands. The highest compressive strength and denser structure of geopolymer concrete is achieved when each type of aluminosilicate is mixed with an alkaline medium separately.

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Section: Resultsmentioning

confidence: 99%

Influence of Mixing Order on the Synthesis of Geopolymer Concrete

et al. 2022

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“…Then, a portion of Al 3+ replaces Ca 2+ to form a C-A-S-H gel [73][74][75][76]. Na + in alkaline solutions combines with Si (OH)4 monomers and Al (OH) − 4 monomers to form N-A-S-H gel [72]. Three gels were found in all three curing conditions of this study, To summarize, the mechanical properties of geopolymers are closely related to morphology, which is impacted by the formation of various hydration products.…”

Section: Xrd Analysismentioning

confidence: 99%

“…Combined with SEM images, it can be seen that heat curing accelerates the dissolution of ions in raw materials, thereby promoting the formation of gels. As the test raw material FA contains a large amount of Si 4+ and Al 3+ and GGBS contains a large amount of Ca 2+ and Si 4+ , OH − in the alkaline solution destroys Ca 2+ , Al 3+ , and Si 4+ in the raw material and releases a large amount of Si (OH) 4 monomer and Al (OH) − 4 monomer, while Ca 2+ and Si (OH) 4 combine to form C-S-H gel [72]. Then, a portion of Al 3+ replaces Ca 2+ to form a C-A-S-H gel [73][74][75][76].…”

Section: Xrd Analysismentioning

confidence: 99%

Study the Mechanical Properties of Geopolymer under Different Curing Conditions

Liu,

Shi,

Zhang

et al. 2023

Minerals

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The geopolymer is an environmentally friendly and high-performance material. Nowadays, how to improve the degree of the geopolymer’s reaction and enhance its mechanical properties has become a hot topic. This study used orthogonal tests to design the precursor mixing ratio, considering GGBS content (A), water/binder ratio (B), and alkaline activator modulus (C). The fly ash (FA) ground granulated blast furnace slag (GGBS)-based geopolymers were cured under two standard curing conditions: 40 °C under water and 40 °C in the oven. Then, the influence of these factors on the mechanical properties of geopolymers under different curing conditions was summarized. The contribution of each factor was ranked, which was used to find out the most sensitive factors affecting the mechanical properties. Taking the 7 days and 28 days of compressive strength and flexural strength of the geopolymer specimens as the evaluation criteria, the optimum ratio method for preparing geopolymers was obtained. Then, the prediction model of compressive strength under different curing conditions was established. SEM and XRD were used to analyze the microstructure and hydration products of the samples. The test results showed that the optimum ratio of FA-based geopolymers varied under different curing conditions. The GGBS content was the key factor in determining the mechanical properties. The heat curing condition was the best curing condition, the 28-day compressive strength could reach 76.3 MPa, and the 28-day flexural strength could reach 7.4 MPa. The prediction models established for compressive strength under different curing conditions had high accuracy. The specimens under the best curing conditions exhibited a dense internal microstructure and the presence of C-S-H gels, C-A-S-H gels, and N-A-S-H gels.

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“…According to Yuan et al (2022), the compressive strength increases as the concentration of alkali solution increases, but beyond that point, the strength decreases. As a result of high concentrations of OH* in the solution, polycondensation was inhibited and the strength of the solution was reduced.…”

Section: Recommendationsmentioning

confidence: 99%

Evaluating the potential of geopolymer concrete as a sustainable alternative for thin white-topping pavement

S.,

Shakor,

Hasan

et al. 2023

Front. Mater.

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Introduction: The construction industry uses a large quantity of natural materials in the production of concrete. Although attempts to incorporate green materials in concrete began years ago, not every building uses such materials today, and roadways, particularly, still rely on unsustainable materials.Methods: Therefore, this study used alternative materials, including fly ash, manufactured sand aggregates, and different molarities of alkaline activators, to incorporate waste byproducts in a geopolymer concrete white-topping pavement layer. Recent developments have led to the emergence of geopolymers as distinct classes of materials. In the 1990s, fly ash-based geopolymers became more popular than other kinds, as they are more efficient compared to Portland cement concrete.Results: Aluminosilicate gel can be obtained by combining fly ash and alkaline solution. A comprehensive literature review of geopolymer concrete was performed in this study. It examines its critical design parameters, including alkaline solutions, curing temperatures, curing methods, workability, and compressive strength under various environmental conditions. This review provides a unique opportunity for researchers to understand how geopolymer concrete performs.Discussion: A range of conditions were investigated to determine how to enhance and use this material in a variety of ways. The fresh characteristics of different mixes were studied using slump and Vee-Bee tests, and the characteristics of the cured concrete mixes were determined using flexural, compressive, and flexural fatigue tests. The results indicated that the use of manufactured sand and fly ash with high-molarity alkaline activators results in a geopolymer concrete with an excellent maximum resistance of 5.1 N/mm2 workability, strength, and fatigue properties, making it suitable for use in roadway pavement.

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Orthogonal analysis and mechanism of compressive strength and microstructure of the metakaolin-fly ash geopolymer

Cited by 7 publications

References 51 publications

Influence of Mixing Order on the Synthesis of Geopolymer Concrete

Influence of Mixing Order on the Synthesis of Geopolymer Concrete

Study the Mechanical Properties of Geopolymer under Different Curing Conditions

Evaluating the potential of geopolymer concrete as a sustainable alternative for thin white-topping pavement

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