Thermally and mechanically treated Greek palygorskite clay as a pozzolanic material

Georgopoulos, George; Badogiannis, Efstratios; Tsivilis, S.; Perraki, Maria

doi:10.1016/j.clay.2021.106306

Cited by 11 publications

(3 citation statements)

References 68 publications

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“…In view of the analysis of the methods related to the pozzolanic reactivity of supplementary cementitious materials (SCMs), especially in calcined clays, it can be observed that the tests, in general, need to be associated with more reliable results [ 76 ]. Pozzolanic potential analyses involve the creation of a medium that resembles, at least in part, the cement hydration reaction, either in temperature, pH or time, causing the calcium hydroxide (C-H) to react with the pozzolanic material.…”

Section: Discussionmentioning

confidence: 99%

“…The determination of the fixed C-H content, known as modified Chapelle, is a method used to assess the reactivity of pozzolanic materials in aqueous media [ 65 , 75 ], based on the ability of the pozzolanic material in addition to fixed lime for the formation of hydrated compounds. This method can be used in several pozzolanic materials; however, many authors consider it an ideal test for calcined clays and metakaolin because it is a process that resembles the hydration of OPC and the consumption of lime with the silica-rich material (pozzolan) [ 76 , 77 , 78 ]. The modified Chapelle test is standardized and performed in a lime–pozzolan aqueous system for 16 h at 90 °C with continuous stirring.…”

Section: Analysis Of Pozzolanic Activitymentioning

confidence: 99%

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Methods for Evaluating Pozzolanic Reactivity in Calcined Clays: A Review

Pinheiro¹,

Alexandre²,

Xavier³

et al. 2023

Materials

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The search for alternative materials to replace ordinary Portland cement has been the object of work that enhances the investigation of the use of pozzolanic materials and the reduction of the carbon footprint with supplementary cementitious materials. However, not all materials are available to meet the large-scale demand for cement replacement. A relevant exception is the calcined clay, a material found worldwide that, when subjected to appropriate heat treatment, presents pozzolanic reactivity and can be used as a supplementary material to cement. This review presents, through a systematic search, methods for measuring the pozzolanic reactivity of calcined clays, namely, direct, indirect, qualitative, quantitative, chemical and physical methods such as electrical conductivity (Lùxan), the force activity index, the modified Chapelle, R3, Frattini test, thermal analysis, X-ray diffraction and X-ray fluorescence spectrometry. The most usual methods to assess the pozzolanic reactivity of calcined clays were exposed and analyzed. It should be pointed out that there is greater use of the Frattini and modified Chapelle methods as well as the analysis of the mechanical strength behavior of the material in cementitious matrices. X-ray diffraction and thermal analysis were exposed as the most used correlation methods but it was also concluded that different tests are needed to generate accurate results.

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Section: Discussionmentioning

confidence: 99%

Section: Analysis Of Pozzolanic Activitymentioning

confidence: 99%

Methods for Evaluating Pozzolanic Reactivity in Calcined Clays: A Review

Pinheiro¹,

Alexandre²,

Xavier³

et al. 2023

Materials

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“…Already in the natural state, aluminosilicates exhibit a noticeable ion-exchange and sorption capacity, and catalytic and molecular sieve properties [47][48][49]. Furthermore, using various types of chemical [50,51], physical [52][53][54] and mechanical [55,56] modifications, a purposeful transformation of the structure, composition and physicochemical properties of aluminosilicates is carried out, creating new complex materials on their basis [37,47,57].…”

Section: Introductionmentioning

confidence: 99%

ZnFe2O4/Zeolite Nanocomposites for Sorption Extraction of Cu2+ from Aqueous Medium

Tomina,

Novikova,

Kotova

et al. 2023

AppliedChem

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In order to enhance the efficiency of heavy metal ion extraction from aqueous medium, new nanocomposite magnetic sorbents were synthesized on the base of natural zeolite (Zt) and nanoparticles of ZnFe2O4 (F). The composition, structure and physical–chemical properties of new composites with 2% (Zt-2F), 8% (Zt-8F) and 16% (Zt-16F) of zinc ferrite were characterized by XRD, BET adsorption–desorption of nitrogen, SEM with elemental mapping, TEM and magnetometry. The sorption capacity of materials was assessed towards Cu2+ ions in aqueous solutions, for which kinetic and equilibrium features of sorption were established. The maximal sorption capacity (amax, mg/g) of the studied materials increased in the order: Zt (19.4) < Zt-2F (27.3) < Zt-8F (30.2) < Zt-16F (32.8) < ZnFe2O4 (161.3). The kinetics of the sorption process followed a pseudo-second order kinetic model. The sorption equilibrium at zinc ferrite was successfully described by the Langmuir model, while the Freundlich model better fitted the sorption equilibrium on zeolite and composites. The efficiency of Cu2+ ion extraction from 320 mg/dm3 aqueous solution was 63% for composite Zt-16F and 100% for a sample of ZnFe2O4. It was established that the proposed composite sorbents provide the operation of several cycles without regeneration, they can be easily recycled with 0.1 N HCl solution and are capable of magnetic separation. The advantages of new composites and the proposed method of synthesis allow recommending these materials as effective sorbents of heavy metals from wastewater.

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