Activación térmica de bentonitas para su utilización como puzolanas

Tironi, Alejandra; Trezza, Mónica Adriana; Irassar, Edgardo F.; Scian, Alberto N.

doi:10.4067/s0718-915x2012000100005

Cited by 8 publications

(10 citation statements)

References 6 publications

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“…Figure 1 shows the X-ray diffraction pattern obtained for the natural pozzolan (NP), where several common minerals can be identified, such as quartz (SiO 2 ), anorthite (Ca(Al 2 Si 2 O 8 )), cordierite (Mg 2 (Al 4 Si 5 O 18 )) and montmorillonite (Na,Ca) 0,3 (Al,Mg) 2 (Si 4 O 10 (OH) 2X H 2 O) plagioclases. The latter, part of the smectite family of the phyllosilicate mineral group, exhibited the highest water adsorption among the clay minerals due to its laminar structure and the charge distribution patterns inside its structure (20). To reduce the demand of water in the geopolymer material, it was necessary to calcine the material at 700 °C, which was performed at a heating rate of 14 °C/min and maintained for 15 minutes.…”

Section: Methodsmentioning

confidence: 99%

Natural pozzolan-and granulated blast furnace slag-based binary geopolymers

Robayo¹,

Gutiérrez²,

Gordillo³

2016

Mater. construcc.

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This study describes the synthesis at ambient temperature (25±3 °C) of binary geopolymer systems based on natural volcanic pozzolan and granulated blast furnace slag. Na 2 SiO 3 and NaOH were used as alkaline activators. The effects of the SiO 2 /Al 2 O 3 , Na 2 O/Al 2 O 3 ratio and the amount of slag added (from 0 to 30%) on the reaction kinetics, compressive strength and microstructure of the final product were studied. To characterise the geopolymer pastes, techniques such as X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used. The results indicate the possibility of obtaining a geopolymer cement with a compressive strength of up to 48.11 MPa after 28 days of curing at ambient temperature whose characteristics are comparable to those of commercial portland cement. RESUMEN: Geopolímeros de tipo binario basados en una puzolana natural y escoria siderúrgica de alto horno.Este trabajo describe la síntesis a temperatura ambiente (25±3 °C) de sistemas geopoliméricos de tipo binario basados en una puzolana natural de origen volcánico y escoria siderúrgica de alto horno usando activadores alcalinos basados en la combinación de Na 2 SiO 3 y NaOH. Se estudió el efecto de la relación SiO 2 /Al 2 O 3 , Na 2 O/ Al 2 O 3 y la cantidad de escoria adicionada en niveles entre el 0 y 30% sobre la cinética de reacción, la resistencia a la compresión y la microestructura del producto final. Para la caracterización de las pastas geopoliméricas se utilizaron técnicas como difracción de rayos X (DRX), espectroscopia infrarroja (FTIR) y microscopia electró-nica de barrido (MEB). Los resultados conseguidos revelan la posibilidad de obtener un cementante geopolimérico con una resistencia a la compresión de hasta 48,11 MPa a los 28 días de curado a temperatura ambiente cuyas características son comparables a las de un cemento portland comercial.

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Section: Methodsmentioning

confidence: 99%

Natural pozzolan-and granulated blast furnace slag-based binary geopolymers

Robayo¹,

Gutiérrez²,

Gordillo³

2016

Mater. construcc.

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“…The results in Table 6 indicate that the treated clay has a higher surface area, therefore it is expected to be more re- active and, in addition, to have a higher average pore size. As some authors have shown, the reactivity of calcined samples is related to their specific surface: the larger the surface, the greater the reactivity (22). Figure 4 shows the radius of the pores against their accumulated volume for clays.…”

Section: Porosimetry and Surface Areamentioning

confidence: 96%

“…The increase in porosity (average size and volume) and in the specific surface area occurs due to the fact that the thermal treatment produces a deterioration of the montmorillonite sheets and that when the interlaminar water is released in the form of vapor, the structure widens and this in turn causes disorder in the structure (22).…”

Section: Porosimetry and Surface Areamentioning

confidence: 99%

“…The behavior of compressive strengths for the WFST aggregate was probably affected by the porosity of the aggregates because after heat treatment, the distribution and pore sizes for the clay were increased (Figure 4). Authors such as (22) mention that after their thermal treatment their clays increased in volume and when they were used in pastes, they caused capillary pores greater than 20 nm in radius, causing detriment to compressive strength and impermeability. The adhesion between the aggregate and the paste could also have been negatively affected contributing to the drop in resistance since, as seen in Figure 11, the water demand of the mortars with WFST is higher, which could allow a larger water film to be generated around the aggregate, increasing the thickness of the interfacial transition zone (ITZ) and therefore decreasing its resistance to compression, as other authors have pointed out (36).…”

Section: Compressive Strengthmentioning

confidence: 99%

“…They have a high percentage of calcium or sodium aluminosilicate and may have non-clay minerals such as anorthite and quartz (21). Authors have reported that it is possible to activate montmorillonite (bentonite) clays for use as supplemental cementitious materials with promising results (22)(23)(24)(25).…”

Section: Introductionmentioning

confidence: 99%

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Substitution of aggregates by waste foundry sand: effects on physical properties of mortars

2021

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The substitution of the normalized aggregate by residual foundry sand (WFS) was studied on the physical properties of mortars by means of resistance to compression and capillary absorption tests. The aggregate was replaced by WFS in its natural state (WFS), washed residual foundry sand (WFSW) and heat treated residual foundry sand (WFST). The WFS had a percentage of bentonite, which was sought to be thermally activated. It was found that the physical behavior of the mortars containing WFS and WFSW was similar to that of the control sample. The clay recovered from the sand washing was evaluated for its pozzolanic potential, it was found that, with the thermal treatment, the montmorillonite acquires pozzolanic behavior. Mortars with WFST presented a drop in compressive strength. The pozzolanic effect achieved in the clay was not reflected in the compressive strength of the mortars with WFST.

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Thermal analysis to assess pozzolanic activity of calcined kaolinitic clays

Tironi

Trezza

Scian

et al. 2014

J Therm Anal Calorim

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The use of calcined clays as partial replacement of cement is encouraged since it promotes the reduction of the green-house gas emission and the energy requirement of cement-based material, maintaining or enhancing the mechanical properties and the durable performance of these materials. In this paper, the use of thermal methods-DTA/TG and calorimetry-to select and to evaluate two kaolinitic clays for their use as pozzolanic materials was explored. The content and crystallinity of kaolinite in clays can be determined by DTA/TG analysis, and this technique is also suitable to select the calcination temperature for complete kaolinite dehydroxylation. Calorimetric analysis on blended cements (30 % by mass of replacement) can differentiate the reactivity of calcined kaolinitic clays. Results show that more reactive calcined kaolinitic clay develops the second and third peaks earlier than those of PC with great intensity and high acceleration. The reactivity of calcined clays is associated to raw materials containing kaolinite with high structural disorder that determines calcined clays with large specific surface area, high grindability, and small mean particles size (d 50 ) for the same grinding objective. Finally, the DTA/TG analysis can determine the type and the amount of hydrated phases obtained at different ages to evaluate the pozzolanic reaction of calcined clay in accordance with the standardized pozzolanic activity index.

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Activación térmica de bentonitas para su utilización como puzolanas

Cited by 8 publications

References 6 publications

Natural pozzolan-and granulated blast furnace slag-based binary geopolymers

Natural pozzolan-and granulated blast furnace slag-based binary geopolymers

Substitution of aggregates by waste foundry sand: effects on physical properties of mortars

Thermal analysis to assess pozzolanic activity of calcined kaolinitic clays

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