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Angel Palomo - One of the best experts on this subject based on the ideXlab platform.
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alternative prime materials for developing new cements Alkaline Activation of alkali aluminosilicate glasses
Ceramics International, 2016Co-Authors: C Ruizsantaquiteria, Ana Fernandezjimenez, Angel PalomoAbstract:Abstract This study explored the use of alkali aluminosilicate glass obtained by melting and quenching common clay, feldspar and fluxing oxides as a possible starting material for Alkaline Activation. The glass was synthesized at two different temperatures (1250 and 1400 °C), using Na 2 O (8 wt%) as a fluxing oxide. The effect of including small amounts of calcium in the starting mix (5.6 wt% of CaO) was likewise studied. The Alkaline Activation of such glasses yielded cements with high compressive strength (65 MPa after 20 h at 85 °C). The presence of calcium in the vitreous network favored the formation of a very compact cementitious matrix. TEM-EDX analyses showed that the gel forming in these systems was compositionally (and presumably structurally) non-uniform, with some local high-calcium, high Si/Al ratio (CASH-type gel) areas co-existing with low calcium and low Si/Al ratio clusters (NASH-type gel).
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effect of calcium on the Alkaline Activation of aluminosilicate glass
Ceramics International, 2016Co-Authors: Ines Garcialodeiro, Ana Fernandezjimenez, E Apariciorebollo, Angel PalomoAbstract:Abstract The present study explored the alkali reactivity of aluminosilicate glass with a variable (from 0 to 40 weight per cent) CaO content. The findings showed that the presence of CaO in the raw mix conditions the formation of vitreous material and post-Activation mechanical strength development. Vitreous matrices with a CaO content of up to 20% are uniform and highly reactive, generating mechanically strong systems after Alkaline Activation. CaO concentrations of 40% or over limit the formation of a vitreous matrix, favouring the synthesis of a very non-uniform system, primarily comprising different types of calcium silicates that are scantly reactive in the presence of Alkaline activators.
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Alkaline Activation of synthetic aluminosilicate glass
Ceramics International, 2014Co-Authors: Ines Garcialodeiro, Ana Fernandezjimenez, P Pena, Angel PalomoAbstract:Abstract The alkali Activation of aluminosilicates is a procedure for obtaining new binders with many of the same properties as traditional portland cement. The type and characteristics of the products formed, however, and consequently their mechanical performance, are conditioned by a number of parameters. The present study explored the potential reactivity of synthetic Alkaline silicoaluminates alkali-activated at high temperatures by analysing parameters such as the chemical composition of the starting material and the vitreous phase content. When alkali-activated, the glass produced in the laboratory developed high mechanical strength, while the performance of the resulting binders was conditioned by the SiO2/Al2O3 ratio in the starting materials. The optimal values were observed to lie between 3 and 4.
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binder chemistry low calcium alkali activated materials
2014Co-Authors: John L Provis, Ana Fernandezjimenez, Elie Kamseu, Cristina Leonelli, Angel PalomoAbstract:Early developments in the developments of low-calcium (including calcium-free) alkali-activated binders were led by the work of Davidovits in France, as noted in Chap. 2. These materials were initially envisaged as a fire-resistant replacement for organic polymeric materials, with identification of potential applications as a possible binder for concrete production following relatively soon afterwards [1]. However, developments in the area of concrete production soon led back to more calcium-rich systems, including the hybrid Pyrament binders, leaving work based on the use of low-calcium systems predominantly aimed at high-temperature applications and other scenarios where the ceramic-like nature of clay-derived alkali-activated pastes was beneficial. Early work in this area was conducted with an almost solely commercial focus, meaning that little scientific information was made available with the exception of a conference proceedings volume [2], several scattered publications in other conferences, and an initial journal publication [3]. Academic research into the Alkaline Activation of metakaolin to form a binder material led to initial publications in the early 1990s [4, 5], and the first description of the formation of a strong and durable binder by Alkaline Activation of fly ash was published by Wastiels et al. [6–8]. With ongoing developments in fly ash Activation, which offers more favourable rheology than is observed in clay-based binders, interest in low-calcium AAM concrete production was reignited, and work since that time in industry and academia has led to the development of a number of different approaches to this problem. A review of the binder chemistry of low-calcium AAM binder systems published in 2007 [9] has since received more than 350 citations in the scientific literature, indicating the high current level of interest in understanding and utilisation of these types of gels.
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variation in hybrid cements over time Alkaline Activation of fly ash portland cement blends
Cement and Concrete Research, 2013Co-Authors: Ines Garcialodeiro, Ana Fernandezjimenez, Angel PalomoAbstract:Abstract The primary aim of the present paper was to determine the variations over time (one year) in the main cementitious gels forming during the Alkaline Activation of hybrid cements (70% FA/30% OPC). The 28 and 365 day hydration products were characterised by different techniques. The findings showed that the C-S-H/N-A-S-H mix of gels precipitating did not precipitate in a pure state, but rather that their composition was affected by the presence of dissolved species. In the presence of aluminium C-S-H gel development was: C-S-H → C–(A)–S–H → C-A-S-H, whilst in the presence of calcium, N-A-S-H gel evolved as follows: N-A-S-H → (N,C)-A-S-H → C-A-S-H. This last conversion is not complete in these systems because the amount of calcium present is thought to be insufficient. On the grounds of the findings, a microstructural model is proposed to describe the development of the reaction products forming in these hybrid cements.
Ana Fernandezjimenez - One of the best experts on this subject based on the ideXlab platform.
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sustainable Alkaline Activation of fly ash aluminium anodising sludge and glass powder blends with a recycled Alkaline cleaning solution
Construction and Building Materials, 2019Co-Authors: Nuno Cristelo, Lisete Fernandes, Ana Fernandezjimenez, F Castro, P B TavaresAbstract:Abstract Introduction of new residues and wastes in the development of Alkaline activated materials is a major concern regarding the spreading and dissemination of this technique. Such increase in the spectrum of available raw materials will decrease the need for long-distance transportation of the more traditional precursors that have been tirelessly used in the past two decades (e.g. fly ash, blast furnace slag). Additionally, the use of commercial activators severely hinders its environmental and financial performance, promoting the need to develop waste-based activators. In this paper, wastes from the aluminium anodising and extrusion processes and from the production of optical lenses were combined with low-calcium fly ash, to produce binders exclusively made from wastes and residues. The performance was assessed through uniaxial compression strength tests, which were accompanied by the monitorisation of several physical properties, including temperature, pH and weight; and by a thorough microscopic analysis, including scanning electron microscopy, coupled with energy dispersive spectroscopy, and x-ray diffraction, for mineralogy characterisation. Results show that the addition of glass powder and aluminium anodising sludge to class-F fly ash optimised the final precursor, which was then successfully activated with a disposed solution, originally used to clean the aluminium extrusion steel dies. The inclusion of soluble silicon and aluminium in the precursor raised the compression strength after short-term curing, compared with pastes prepared only with fly ash.
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alternative prime materials for developing new cements Alkaline Activation of alkali aluminosilicate glasses
Ceramics International, 2016Co-Authors: C Ruizsantaquiteria, Ana Fernandezjimenez, Angel PalomoAbstract:Abstract This study explored the use of alkali aluminosilicate glass obtained by melting and quenching common clay, feldspar and fluxing oxides as a possible starting material for Alkaline Activation. The glass was synthesized at two different temperatures (1250 and 1400 °C), using Na 2 O (8 wt%) as a fluxing oxide. The effect of including small amounts of calcium in the starting mix (5.6 wt% of CaO) was likewise studied. The Alkaline Activation of such glasses yielded cements with high compressive strength (65 MPa after 20 h at 85 °C). The presence of calcium in the vitreous network favored the formation of a very compact cementitious matrix. TEM-EDX analyses showed that the gel forming in these systems was compositionally (and presumably structurally) non-uniform, with some local high-calcium, high Si/Al ratio (CASH-type gel) areas co-existing with low calcium and low Si/Al ratio clusters (NASH-type gel).
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effect of calcium on the Alkaline Activation of aluminosilicate glass
Ceramics International, 2016Co-Authors: Ines Garcialodeiro, Ana Fernandezjimenez, E Apariciorebollo, Angel PalomoAbstract:Abstract The present study explored the alkali reactivity of aluminosilicate glass with a variable (from 0 to 40 weight per cent) CaO content. The findings showed that the presence of CaO in the raw mix conditions the formation of vitreous material and post-Activation mechanical strength development. Vitreous matrices with a CaO content of up to 20% are uniform and highly reactive, generating mechanically strong systems after Alkaline Activation. CaO concentrations of 40% or over limit the formation of a vitreous matrix, favouring the synthesis of a very non-uniform system, primarily comprising different types of calcium silicates that are scantly reactive in the presence of Alkaline activators.
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Alkaline Activation of synthetic aluminosilicate glass
Ceramics International, 2014Co-Authors: Ines Garcialodeiro, Ana Fernandezjimenez, P Pena, Angel PalomoAbstract:Abstract The alkali Activation of aluminosilicates is a procedure for obtaining new binders with many of the same properties as traditional portland cement. The type and characteristics of the products formed, however, and consequently their mechanical performance, are conditioned by a number of parameters. The present study explored the potential reactivity of synthetic Alkaline silicoaluminates alkali-activated at high temperatures by analysing parameters such as the chemical composition of the starting material and the vitreous phase content. When alkali-activated, the glass produced in the laboratory developed high mechanical strength, while the performance of the resulting binders was conditioned by the SiO2/Al2O3 ratio in the starting materials. The optimal values were observed to lie between 3 and 4.
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binder chemistry low calcium alkali activated materials
2014Co-Authors: John L Provis, Ana Fernandezjimenez, Elie Kamseu, Cristina Leonelli, Angel PalomoAbstract:Early developments in the developments of low-calcium (including calcium-free) alkali-activated binders were led by the work of Davidovits in France, as noted in Chap. 2. These materials were initially envisaged as a fire-resistant replacement for organic polymeric materials, with identification of potential applications as a possible binder for concrete production following relatively soon afterwards [1]. However, developments in the area of concrete production soon led back to more calcium-rich systems, including the hybrid Pyrament binders, leaving work based on the use of low-calcium systems predominantly aimed at high-temperature applications and other scenarios where the ceramic-like nature of clay-derived alkali-activated pastes was beneficial. Early work in this area was conducted with an almost solely commercial focus, meaning that little scientific information was made available with the exception of a conference proceedings volume [2], several scattered publications in other conferences, and an initial journal publication [3]. Academic research into the Alkaline Activation of metakaolin to form a binder material led to initial publications in the early 1990s [4, 5], and the first description of the formation of a strong and durable binder by Alkaline Activation of fly ash was published by Wastiels et al. [6–8]. With ongoing developments in fly ash Activation, which offers more favourable rheology than is observed in clay-based binders, interest in low-calcium AAM concrete production was reignited, and work since that time in industry and academia has led to the development of a number of different approaches to this problem. A review of the binder chemistry of low-calcium AAM binder systems published in 2007 [9] has since received more than 350 citations in the scientific literature, indicating the high current level of interest in understanding and utilisation of these types of gels.
Nuno Cristelo - One of the best experts on this subject based on the ideXlab platform.
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sustainable Alkaline Activation of fly ash aluminium anodising sludge and glass powder blends with a recycled Alkaline cleaning solution
Construction and Building Materials, 2019Co-Authors: Nuno Cristelo, Lisete Fernandes, Ana Fernandezjimenez, F Castro, P B TavaresAbstract:Abstract Introduction of new residues and wastes in the development of Alkaline activated materials is a major concern regarding the spreading and dissemination of this technique. Such increase in the spectrum of available raw materials will decrease the need for long-distance transportation of the more traditional precursors that have been tirelessly used in the past two decades (e.g. fly ash, blast furnace slag). Additionally, the use of commercial activators severely hinders its environmental and financial performance, promoting the need to develop waste-based activators. In this paper, wastes from the aluminium anodising and extrusion processes and from the production of optical lenses were combined with low-calcium fly ash, to produce binders exclusively made from wastes and residues. The performance was assessed through uniaxial compression strength tests, which were accompanied by the monitorisation of several physical properties, including temperature, pH and weight; and by a thorough microscopic analysis, including scanning electron microscopy, coupled with energy dispersive spectroscopy, and x-ray diffraction, for mineralogy characterisation. Results show that the addition of glass powder and aluminium anodising sludge to class-F fly ash optimised the final precursor, which was then successfully activated with a disposed solution, originally used to clean the aluminium extrusion steel dies. The inclusion of soluble silicon and aluminium in the precursor raised the compression strength after short-term curing, compared with pastes prepared only with fly ash.
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stiffness behavior of soil stabilized with alkali activated fly ash from small to large strains
International Journal of Geomechanics, 2017Co-Authors: Sara Rios, Nuno Cristelo, Antonio Viana Da Fonseca, Cristiana FerreiraAbstract:AbstractAlkaline Activation of fly ash creates a geopolymeric cement that can replace ordinary portland cement in several applications such as soil improvement, with the advantage of much lower carbon dioxide emissions and reusing an industrial by-product otherwise landfilled, which averts several environmental problems. In this paper, the behavior of a silty sand improved by the Alkaline Activation of fly ash is analyzed from small to large strains by presenting uniaxial and drained triaxial compression test results and seismic wave velocities measured throughout the curing period. The dynamic, cyclic, and static tests showed a significant increase in stiffness with curing time, even beyond the 28-day curing period. On the basis of the nondestructive wave-propagation technique, the increase of the shear and compression wave velocities with time were drawn, giving the evolution of the elastic shear modulus and the Poisson ratio values. The dynamic Young modulus was compared to the correspondent secant You...
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rammed earth construction with granitic residual soils the case study of northern portugal
Construction and Building Materials, 2013Co-Authors: Rui André Martins Silva, Nuno Cristelo, Daniel V. Oliveira, Tiago F. S. Miranda, Maria C Escobar, Edgar SoaresAbstract:Abstract Building in unstabilised rammed earth results in low environmental impact. However, northern Portugal has not historical tradition with this technique, and thus the suitability of the local granitic residual soils is unknown. This paper presents an experimental investigation, where this possibility is assessed. The results showed that these soils are unsuitable, and that rammed earth construction is only feasible if these soils go through a stabilising process. The Alkaline Activation of fly ash was investigated as an environmentally friendly stabilisation technique, and it proved to be capable of improving the performance of rammed earth.
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Conservation and new construction solutions in rammed earth
Structural Rehabilitation of Old Buildings, 2013Co-Authors: Rui André Martins Silva, Paul Jaquin, Daniel V. Oliveira, Tiago F. S. Miranda, Luc Schueremans, Nuno CristeloAbstract:The conservation and rehabilitation of several sites of cultural heritage and of the large housing stock built from rammed earth requires adopting intervention techniques that aim at their repair or strengthening. The present work discusses the main causes of the decay of rammed earth constructions. The intervention techniques used to repair cracks and lost volumes of material are also discussed. Regarding the strengthening of rammed earth walls, the discussion is focused on the techniques that improve the out-of-plane behaviour. Special attention is given to the injection of mud grouts for crack repair in rammed earth walls, including the presentation of the most recent developments on the topic, namely regarding their fresh-state rheology, hardened-state strength and adhesion. Finally, the use of the rammed earth is discussed as a modern building solution. In addition, several typical techniques for improving rammed earth constructions are discussed, aiming at adequate those to modern demands. In addition, the Alkaline Activation of fly ash is presented and discussed as a novel improvement technique.
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soil stabilisation using Alkaline Activation of fly ash for self compacting rammed earth construction
Construction and Building Materials, 2012Co-Authors: Nuno Cristelo, Stephanie Glendinning, Daniel V. Oliveira, Tiago F. S. Miranda, Rui André Martins SilvaAbstract:Abstract This paper studies the effectiveness of Alkaline Activation of low-calcium fly ash on the improvement of residual granitic soils to be used on rammed-earth construction. Different liquid:solid ratios, alkali concentrations and Na 2 O:ash ratios were tested. Effect of calcium hydroxide, sodium chloride and concrete superplasticiser is also reported. Compressive strength up to 7 days at 60 °C was determined. Results show that there is an optimum value for the activator:solids ratio and the alkali concentration, and that a decrease in the Na 2 O:ash ratio results in a strength increase. No improvement was observed with the sodium chloride or the superplasticiser, while the calcium produced only a short term increase in strength. SEM/EDS analysis were used to analyse microstructural development, showing that strength is fairly related to the Si:Al and Na:Si ratios.
F Puertas - One of the best experts on this subject based on the ideXlab platform.
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study of synergy between a natural volcanic pozzolan and a granulated blast furnace slag in the production of geopolymeric pastes and mortars
Construction and Building Materials, 2017Co-Authors: Rafael Andres Robayosalazar, Mejia De Gutierrez, F PuertasAbstract:Abstract The production and characterization of a cement and mortar based on the Alkaline Activation of a high content (≥70%) of natural volcanic pozzolan (NP) and the synergic effect of the addition of granulated blast furnace slag (GBFS) up to 30% were performed. NaOH and a mixture of NaOH + Na 2 SiO 3 were used as activators. The results of this study highlight the possibility of obtaining a binder with a compressive strength of up to 125 MPa at 28 days of curing (25 °C). The optimal Alkaline cement that was obtained can be categorized as GU- and LH-type cement according to the ASTM C1157 standard.
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waste glass as a precursor in Alkaline Activation chemical process and hydration products
Construction and Building Materials, 2017Co-Authors: M Torrescarrasco, F PuertasAbstract:Abstract This paper discusses the results of alkali-activating waste glass in pursuit of a new type of alkali activated materials (AAMs). Waste glass pastes were prepared with different Alkaline activators (NaOH, NaOH/Na 2 CO 3 , sodium silicate hydrate and KOH) with different concentrations and cured for 20 h at 85 °C and at 99% or 6.5% relative humidity to assess the effect of these variables on paste mechanical strength and microstructure. Compressive strength performance was better at the higher Alkaline concentrations and when the pastes were cured at low relative humidity (6.5%), which induced low porosity (MIP) and high specific surface (BET). Irrespective of the type of activator or curing process, the main reaction product was a Si-high, Al-low gel. As a raw material for Alkaline cement manufacture, waste glass delivered compact, high-strength cementitious skeletons.
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rice husk ash as a source of silica in alkali activated fly ash and granulated blast furnace slag systems
Materiales De Construccion, 2013Co-Authors: Johanna M Mejia, Mejía R. De Gutiérrez, F PuertasAbstract:This study assesses the viability of using an agro-industrial by-product, rice husk ash (RHA) from a Colombian rice company’s combustion facility, as a total replacement for the commercial sodium silicate ordinarily used in alkaliactivated binders. Fly ash (FA), granulated blast furnace slag (GBFS) and binary 50FA:50GBFS blended pastes were activated with a mix of sodium hydroxide and either sodium silicate or one of two types of RHA. The pastes were characterised for strength, mineralogy and microstructure. The findings showed that the agro-industrial by-product can be used to yield alkali-activated materials with 7-day mechanical strengths on the order of 42 MPa. The study confirmed that both amorphous silica and part of the crystalline silica present in RHA participate in the Alkaline Activation process, providing the alkalinity is suitably adjusted.
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mineralogical and microstructural characterisation of alkali activated fly ash slag pastes
Cement & Concrete Composites, 2003Co-Authors: F Puertas, Ana FernandezjimenezAbstract:Abstract A mechanical, mineralogical and microstructural characterisation of the cement pastes obtained by Alkaline Activation of fly ash/slag mixtures cured at different temperatures has been carried out. The pastes obtained were characterised by XRD, FTIR, MAS NMR, SEM/EDX, atomic absorption and ion chromatography, also the insoluble residue in HCl was determined. The results obtained have proved the existence of two different reaction products in those activated pastes. The average atomic ratios in the main reaction product were Ca/Si∼0.8, Al/Ca∼0.6, Si/Al∼2–3. Such analysis corresponds to calcium silicate hydrate rich in Al, which includes Na in its structure. Other reaction product which was detected in the pastes as result of fly ash Activation, was an Alkaline aluminosilicate hydrate with a three-dimensional structure.
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determination of kinetic equations of Alkaline Activation of blast furnace slag by means of calorimetric data
Journal of Thermal Analysis and Calorimetry, 1998Co-Authors: Ana Fernandezjimenez, F Puertas, A ArteagaAbstract:The Alkaline Activation of blast furnace slag promotes the formation of new cement materials. These materials have many advantages over ordinary Portland cement, including high strength, low production cost and good durability. However, many aspects of the chemistry of Alkaline activated slags are not yet very well understood. Some authors consider that these processes occur through a heterogeneous reaction, and that they can be governed by three mechanisms: a) nucleation and growth of the hydrated phase; b) phase boundary interactions and c) any diffusion process though the layer of hydration products.
Rui André Martins Silva - One of the best experts on this subject based on the ideXlab platform.
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rammed earth construction with granitic residual soils the case study of northern portugal
Construction and Building Materials, 2013Co-Authors: Rui André Martins Silva, Nuno Cristelo, Daniel V. Oliveira, Tiago F. S. Miranda, Maria C Escobar, Edgar SoaresAbstract:Abstract Building in unstabilised rammed earth results in low environmental impact. However, northern Portugal has not historical tradition with this technique, and thus the suitability of the local granitic residual soils is unknown. This paper presents an experimental investigation, where this possibility is assessed. The results showed that these soils are unsuitable, and that rammed earth construction is only feasible if these soils go through a stabilising process. The Alkaline Activation of fly ash was investigated as an environmentally friendly stabilisation technique, and it proved to be capable of improving the performance of rammed earth.
-
Conservation and new construction solutions in rammed earth
Structural Rehabilitation of Old Buildings, 2013Co-Authors: Rui André Martins Silva, Paul Jaquin, Daniel V. Oliveira, Tiago F. S. Miranda, Luc Schueremans, Nuno CristeloAbstract:The conservation and rehabilitation of several sites of cultural heritage and of the large housing stock built from rammed earth requires adopting intervention techniques that aim at their repair or strengthening. The present work discusses the main causes of the decay of rammed earth constructions. The intervention techniques used to repair cracks and lost volumes of material are also discussed. Regarding the strengthening of rammed earth walls, the discussion is focused on the techniques that improve the out-of-plane behaviour. Special attention is given to the injection of mud grouts for crack repair in rammed earth walls, including the presentation of the most recent developments on the topic, namely regarding their fresh-state rheology, hardened-state strength and adhesion. Finally, the use of the rammed earth is discussed as a modern building solution. In addition, several typical techniques for improving rammed earth constructions are discussed, aiming at adequate those to modern demands. In addition, the Alkaline Activation of fly ash is presented and discussed as a novel improvement technique.
-
soil stabilisation using Alkaline Activation of fly ash for self compacting rammed earth construction
Construction and Building Materials, 2012Co-Authors: Nuno Cristelo, Stephanie Glendinning, Daniel V. Oliveira, Tiago F. S. Miranda, Rui André Martins SilvaAbstract:Abstract This paper studies the effectiveness of Alkaline Activation of low-calcium fly ash on the improvement of residual granitic soils to be used on rammed-earth construction. Different liquid:solid ratios, alkali concentrations and Na 2 O:ash ratios were tested. Effect of calcium hydroxide, sodium chloride and concrete superplasticiser is also reported. Compressive strength up to 7 days at 60 °C was determined. Results show that there is an optimum value for the activator:solids ratio and the alkali concentration, and that a decrease in the Na 2 O:ash ratio results in a strength increase. No improvement was observed with the sodium chloride or the superplasticiser, while the calcium produced only a short term increase in strength. SEM/EDS analysis were used to analyse microstructural development, showing that strength is fairly related to the Si:Al and Na:Si ratios.