Effect of NaOH concentration on properties and microstructure of a novel reactive ultra-fine fly ash geopolymer

Chen, Kailun; Lin, Wei‐Ting; Liu, Weidong

doi:10.1016/j.apt.2021.06.008

Cited by 53 publications

(16 citation statements)

References 40 publications

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“…This mass loss of the metakaolin geopolymer is probably due to the loss of weakly bound water. This is in agreement with the literature that associates this mass loss with the loss of remaining free water and slightly bound water in the geopolymer structure [72,73]. Accordingly, two endothermic peaks are visible in the DSC curve.…”

Section: Thermal Analysis (Tga/dsc)supporting

confidence: 92%

“…Accordingly, two endothermic peaks are visible in the DSC curve. From 200 to 600 °C, a further 3% mass loss is observed and is associated with the loss of bound water generated by the polymerization reaction of silanol and aluminol group (Si-OH and Al-OH) on the surface gels (dehydration of N-A-S-H gel) [59,73].…”

Section: Thermal Analysis (Tga/dsc)mentioning

confidence: 99%

“…It can also be seen that all the metakaolin-based geopolymers present this amorphous hump between 15 to 40° 2θ. The literature [73] relates this broad peak to the formation of N-A-S-H gel, and the size of it depends on the amount of gel produced. It has also been observed that in metakaolin geopolymers those broad peaks are shifted to higher 2θ angles.…”

Section: Xrd Analysismentioning

confidence: 99%

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Influence of sodium-based activators and water content on the fresh and hardened properties of metakaolin geopolymers

et al. 2022

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Several studies explore optimal molar oxide ratios for metakaolin geopolymer production. However, there is not a consensus on the optimal mix, and within similar range large differences in compressive strength are reported, and consequently in the overall performance. Hence, the present work selects a specific molar oxide ratio that leads to strengths above 30 MPa (SiO2/Al2O3 ratio of 3.19, a Na2O/Al2O3 of 1.00, and a water-to-solids ratio of 0.52), and investigates the individual effect of the sodium-based activators (NaOH and Na2SiO3) and the water content on fresh and hardened properties of metakaolin geopolymers. The tested properties include the rheology, setting time, mass loss, shrinkage, density and compressive strength. The test results show that an increase of water content (water-to-solids > 0.52) and increase of NaOH (Na2O/Al2O3 > 1.03) have the largest impact, showing a detrimental effect on both fresh and hardened properties. Moreover, the best results are obtained when using molar ratios of SiO2/Al2O3 at 3.14, Na2O/Al2O3 at 0.97 and a water-to-solids ratio of 0.51, which is within the range of optimum molar ratios from previous studies. The tests are further supplemented by Thermogravimetric analysis/Differential scanning calorimetry (TGA/DSC), scanning electron microscopy (SEM), and X-ray diffraction (XRD).

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Section: Thermal Analysis (Tga/dsc)supporting

confidence: 92%

Section: Thermal Analysis (Tga/dsc)mentioning

confidence: 99%

Section: Xrd Analysismentioning

confidence: 99%

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Influence of sodium-based activators and water content on the fresh and hardened properties of metakaolin geopolymers

et al. 2022

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“…Chen et al [46] reported the FT-IR bands observed in reactive ultrafine (RUFA)-based geopolymer consistent with the literature. The absorption bands cm −1 and 3480 cm −1 are the bending vibrations of H-O-H and -OH, confirming ence of water molecules in the sample, and 460 cm −1 is the in-plane bending vib Si-O-Si ,while the band at 728 cm −1 indicates the presence of Si-O-Al bending v At 1093 cm -1 of fly ash, the band shifted after alkali activation to 1044 cm −1 , 1026 cm cm −1 , and 1002 cm −1 [47].…”

Section: Scanning Electron Microscopy With Energy-dispersive Spectros...supporting

confidence: 71%

Geopolymers as Sustainable Material for Strengthening and Restoring Unreinforced Masonry Structures: A Review

et al. 2021

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Unreinforced masonry (URM) structures are vulnerable to earthquakes; thus, materials and techniques for their strengthening and restoration should be developed. However, the materials used in some of the existing retrofitting technologies for URM and the waste produced at its end-of-life are unsustainable. The production of ordinary Portland cement (OPC) worldwide has enormously contributed to the global carbon footprint, resulting in persistent environmental problems. Replacing OPC with geopolymers, which are more sustainable and environmentally friendly, presents a potential solution to these problems. Geopolymers can replace the OPC component in engineering cementitious composites (ECC), recommended to strengthen and restore URM structures. In the present paper, the state-of-the-art knowledge development on applying geopolymers in URM structures is discussed. The discussion is focused on geopolymers and their components, material characterization, geopolymers as a strengthening and restoration material, and fiber-reinforced geopolymers and their application to URM structures. Based on this review, it was found that the mechanical properties of geopolymers are on par with that of OPC; however, there are few studies on the mentioned applications of geopolymers. The characterization of geopolymers’ mechanical and physical properties as a restoration material for URM structures is still limited. Therefore, other properties such as chemical interaction with the substrate, workability, thixotropic behavior, and aesthetic features of geopolymers need to be investigated for its wide application. The application method of geopolymer-based ECC as a strengthening material for a URM structure is by grouting injection. It is also worth recommending that other application techniques such as deep repointing, jacketing, and cement-plastering be explored.

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“…After adding an alkaline activator, each aggregate sample exhibits an absorption peak at 1400–1450 cm −1 originating from the C-O stretching vibration. This indicates that free ions in the aggregate react with CO 2 and the sample becomes carbonized [ 45 ], probably during the experimental testing or in the dryer. The stretching vibration of -OH in the range of 3250–3750 cm −1 [ 46 ] originates from the presence of structural water and free water.…”

Section: Microstructural Characterizationmentioning

confidence: 99%

Preparation and Characterization of the Functional Properties of Synthetic Aggregates from Silico-Manganese Slag

et al. 2021

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A large number of natural aggregates are used in the field of construction materials, resulting in the exhaustion of natural aggregates. Therefore, looking for an alternative will slow down the consumption of natural aggregates. The sintering method not only consumes a lot of energy to prepare aggregates but also produces a lot of pollutants. In this study, silico-manganese (SM) slag was dried, ground into powder, and used as raw material. Solid and liquid alkaline activator methods were used to prepare SM slag non-burning aggregate (SMNA) by the cold bonding method. The effects of grinding time, amounts of solid and liquid alkaline activators, curing temperature, and the amount of added fly ash on aggregate properties were investigated. The aggregate microstructure was characterized by XRD, SEM, and FTIR methods, and the toxic leaching analysis of aggregate was performed. The results showed that with a fixed amount of liquid activator (16.2% wt.) and solid activator (15% wt.) and fly ash (20% wt.), respectively, and curing was performed at room temperature, the aggregate properties were optimal: the bulk density of 1236.6–1476.9 kg/m3 and the water absorption lower than 4.9–5.5%. The apparent density was 1973.1–2281.6 kg/m3, and the bulk crushing strength was 24.7–27.9 MPa. The XRD, SEM, and FTIR results indicated that amorphous gel could be formed from SM under an alkaline activator, improving the aggregate strength. The results of toxic leaching showed that the aggregate prepared from SM exhibited environmentally friendly characteristics. The SMNA was obtained via the simple and low-energy consumption production process, paving the new way toward large-scale utilization of SM.

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Effect of NaOH concentration on properties and microstructure of a novel reactive ultra-fine fly ash geopolymer

Cited by 53 publications

References 40 publications

Influence of sodium-based activators and water content on the fresh and hardened properties of metakaolin geopolymers

Influence of sodium-based activators and water content on the fresh and hardened properties of metakaolin geopolymers

Geopolymers as Sustainable Material for Strengthening and Restoring Unreinforced Masonry Structures: A Review

Preparation and Characterization of the Functional Properties of Synthetic Aggregates from Silico-Manganese Slag

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