Effect of acid attack on microstructure and composition of metakaolin-based geopolymers: The role of alkaline activator

Bouguermouh, Karima; Bouzidi, Nedjima; Mahtout, Leila; Pérez‐Villarejo, Luis; Martínez-Cartas, María Lourdes

doi:10.1016/j.jnoncrysol.2017.03.011

Cited by 70 publications

(37 citation statements)

References 33 publications

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“…Very little change upon the acid attack was observed in GPM-60, particularly for HCl acid attack, which is in agreement with results reported by Bouguermouh et al [39] for metakaolin based geopolymers. Following the H2SO4 attack, a small peak corresponding to gypsum was identified at 2θ of 11.7° in the XRD pattern, revealing that calcium in the calcined lithomarge reacted with H2SO4 to form gypsum.…”

Section: Xrdsupporting

confidence: 91%

“…Recently, a promising solution has emerged in the form of geopolymer binders which have been reported to have improved resistance to sulfate [27][28][29][30][31][32][33] and acid attack [21,27,30,31,[34][35][36][37][38][39] due to their ceramic-like microstructure.…”

Section: Introductionmentioning

confidence: 99%

“…Sulfate and acid attack on clay based geopolymer binder systems has previously been investigated using geopolymers formulated with pure metakaolin [27,33,36,38,39]. In order to encourage the use of less expensive kaolin geopolymer binders, this research aimed to assess and directly compare the resistance of lithomarge-based geopolymer and neat…”

Section: Introductionmentioning

confidence: 99%

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Sulfate and acid resistance of lithomarge-based geopolymer mortars

Kwasny

Aiken

Soutsos

et al. 2018

Construction and Building Materials

101

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2018). Sulfate and acid resistance of lithomarge-based geopolymer mortars. Construction and Building Materials, 166,[537][538][539][540][541][542][543][544][545][546][547][548][549][550][551][552][553] ABSTRACTThe resistance of room temperature cured geopolymer mortars (GPM) against chemical attacks, i.e. sodium and magnesium sulfate solutions, and sulfuric and hydrochloric acid solutions, was evaluated. GPMs were formulated using a lithomarge precursor (low-purity kaolin) to achieve 28-day characteristic compressive strengths of 37.5 and 60 MPa. Their performance was compared with those of equivalent Portland cement mortars (PCMs) having the same paste volume and strength grade. GPMs with both strength grades showed superior performance against sulfate attack when compared to PCMs. No visual deterioration was observed in GPMs, the mass and length changes were relatively small, and no changes to the microstructure were detected -in contrast to severely deteriorated PCMs.As confirmed by visual observations and lower mass loss, GPMs showed better resistance to attack by both acids than PCMs. GPMs provided a better quality (lower permeability) of an acid-degraded layer, lowering the degree of further deterioration. The main mechanisms of the matrix deterioration of GPMs in both acids was dealumination of the hardened binder, with a higher degree of changes detected for sulfuric acid.

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Section: Xrdsupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sulfate and acid resistance of lithomarge-based geopolymer mortars

Kwasny

Aiken

Soutsos

et al. 2018

Construction and Building Materials

101

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“…After calcination, the characteristic peaks of kaolinite have disappeared as shown in the CKT spectrum. This disappearance can be explained by transformation of kaolinite phase present in KT to an amorphous phase metakaolinite which prove dehydroxylation of kaolinite [35,36].…”

Section: Raw Materials Xrd and Fx Characterizationmentioning

confidence: 99%

Efficiency of stabilization/solidification of heavy metals contained in hydroxide sludge waste into metakaolin based geopolymers

Chaabane

Moussaceb

Aït‐Mokhtar

2018

Env Prog and Sustain Energy

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In this work, the S/S of heavy metals contained in hydroxide sludge waste was used into geopolymers. Metakaolin, sludge waste, hydroxide, and sodium silicate were mixed. Amount of waste added varied between 10% and 40% in the synthesis of geopolymers. Geopolymers were cured at 40°C for 24 h. After 7 and 28 days of aging, strength of the geopolymers specimen were studied. Mineralogical phases, morphology and FTIR analysis were used to characterize raw materials and geopolymers. TCLP test was used to determine amount of heavy metals released from S/S materials. Amount of heavy metals released are lower than quantities released from raw waste. Heavy metals were identified, by XRD analysis, within mineralogical phases. Results obtained shows that geopolymers can immobilize heavy metals and reduce their release to the environment. Mechanical strengths of all samples are higher than the lower required for the S/S processes. Best mechanical strength was of 9.29 and 10.02 MPa at 7 and 28 days, respectively. A decrease of mechanical strengths recorded is due to increasing amount of waste added that causes structural discontinuity within the gel during geopolymerization. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13137, 2019

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“…Adicionalmente, picos presentes na matéria-prima permaneceram no padrão geopolimérico, tais como a caulinita (2θ = 20,90º,36,54º,50,20º,75,a muscovita (2θ = 36,42º,45,90º,54,80º,60,) e a hematita (2θ = 36,5º, 50º -ICSD -15840) (ZHANG et al, 2012;BOUGUERMOUH et al, 2017;WAN et al, 2017a).…”

Section: Tenacidadeunclassified

Geopolímero à base de metacaulim com adição de fibras de sisal

Alves¹

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In the present context, geopolymer appears as an ecologically viable alternative compared to Portland cement, due to lower CO2 emissions rate, which, the first mentioned is defined as a binder material whose hardening process takes place in alkaline medium. The objective of this work was to produce and characterize geopolymer paste reinforced with long sisal fibers by means of parameters such as flexural strength and toughness. In this work, metakaolin was used as an aluminosilicate source material in addition to a combination of sodium silicate and sodium hydroxide as the activator solution. The brittle behavior, when submitted to flexion, was improved with the incorporation of elongated sisal fibers. In this study, the variables studied were the percentage of fibers in the composite, the ratio between the amount of activator and base material and the cure time. The statistical model of central composite planning was used in order to optimize the results obtained. Subsequently, X-ray diffraction and scanning electron microscopy analyzes were used to analyze the microstructure of the final composite. Optimized values of modulus of rupture equal to 9.20 MPa are found for approximately 2 days of cure in which the activator / metakaolin ratio is 0.59 and the percentage of fiber is 4.34%, by volume. In addition, modulus values of 3.19 GPa are obtained using 5.15% by volume of sisal fiber, an activator / metakaolin ratio of 0.41 and approximately 7 days cure. Finally, the optimization of the tenacity results happens with the use of 5.19% of fiber, in volume, a cure time of 7 days and a ratio between activator and binder of 0.55, reaching a result of 2.09 kJ/m 2. It is concluded, therefore, that the addition of long sisal fibers increases the modulus of rupture, the modulus of elasticity and the toughness of the geopolymer matrix.

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Effect of acid attack on microstructure and composition of metakaolin-based geopolymers: The role of alkaline activator

Cited by 70 publications

References 33 publications

Sulfate and acid resistance of lithomarge-based geopolymer mortars

Sulfate and acid resistance of lithomarge-based geopolymer mortars

Efficiency of stabilization/solidification of heavy metals contained in hydroxide sludge waste into metakaolin based geopolymers

Geopolímero à base de metacaulim com adição de fibras de sisal

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