Ana Fernández-Jiménez

Ana Fernández-Jiménez
Spanish National Research Council | CSIC · Eduardo Torroja Institute for Construction Science (IETcc)

Ph.D

About

198
Publications
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22,399
Citations
Citations since 2017
48 Research Items
14187 Citations
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201720182019202020212022202305001,0001,5002,0002,5003,000
201720182019202020212022202305001,0001,5002,0002,5003,000
201720182019202020212022202305001,0001,5002,0002,5003,000

Publications

Publications (198)
Article
Full-text available
This work aims to assess the potential reactivity of a mechanically activated kaolin for its use as an alternative cement precursor. The mechanical activation was successfully achieved by grinding at different rotation speeds (250, 300, and 350 rpm) and times (60, 90, and 120 min), obtaining a highly amorphous and reactive material. The amorphizati...
Article
Full-text available
This paper aimed to study the physical and chemical changes taking places in a hybrid alkaline-belite cement (HYP, with a high level of fly ash, 47.5%) paste at high temperature. To investigate the influence of chemical and mineralogical differences on the behavior of cementitious materials when exposed to high temperature, an alkaline-activated fl...
Article
Landfilling of mine and industrial waste streams leads to environmental and economic issues. Sustainable management methods through valorization in manufacturing green construction materials are a current research interest. Here, a promising process for recycling mine tailings, such as phosphate sludge, is proposed. A mixture of phosphate sludge, k...
Preprint
Early-age hydration with neutral or alkaline (0 M to 8 M) solutions was studied in calcium sulfoaluminate clinker (CSA) using isothermal conduction calorimetry, X-ray diffraction (both continuous and discontinuous, i.e., after detaining hydration with isopropanol) and infrared spectroscopy. Hydration in 0.1 M NaOH was observed to be similar to hydr...
Article
Full-text available
This review undertakes rigorous analysis of much of the copious literature available to the scientific community on the use of alkali-activated binders (AABs) in construction. The authors’ main intention is to categorically refute arguments of that part of the scientific community underestimating or even dismissing the actual potential of AABs as a...
Article
Full-text available
The sustainability of resources is becoming a worldwide concern, including construction and building materials, especially with the alarming increase rate in global population. Alternative solutions to ordinary Portland cement (OPC) as a concrete binder are being studied, namely the so-called alkali-activated cements (AAC). These are less harmful t...
Article
The feasibility of transforming the residues of cultivation of two rocks into secondary raw materials through the alkali activation process has been assessed. Mixtures of a sulfate-bearing kaolinitic clay (L02-K) and a sludge derived by the sewing of Pietra Serena stone (sPS) have been investigated. These materials were preliminarily treated at hig...
Article
An innovative hybrid cement, based on type F fly ash (FA), iron and steel slag (ISS) and Portland cement (OPC), is proposed in the present paper. The precursors were activated by powder-form elements – sodium sulphate or sodium chloride – forming what is known as a ‘one part geopolymer’ cement, which was then evaluated considering both mechanical a...
Article
Initial hydration and setting were continuously monitored in calcium sulfoaluminate clinker (KCSA) mixed with water or 2 M NaOH with isothermal conduction calorimetry, ultrasonic pulse velocity (UPV) measurement, the Vicat apparatus, and (in- and ex-situ) X-ray diffraction. P-wave acceleration (ap) proved highly useful to detect very rapid initial...
Article
Full-text available
Facing the beginning of the third decade of the twenty-first century, humanity faces an environmental threat that can pose some serious concerns regarding the life on the planet as we know it. The industrial sector is probably the most significant contributor to this concerning scenario, with the construction industry (CI) playing a leading role. M...
Conference Paper
Study about the effect of chloride ion on ye’elimite (C4A3$) hydration shows formation of chloroaluminates as Friedel’s salt or modifying the morphology of ettringite, however investigations of this salt in sulfoaluminate cement (CSA) was not yet studied. This paper examines the impact of hydration kinetics of CSA with chloride salts (NaCl and CaCl...
Article
Full-text available
The development of alternative materials for the construction industry, based on different types of waste, is gaining significant importance in recent years. This is mostly due to the need to increase sustainability of this heavily polluting activity, thus mitigating the dependence on, for instance, Portland cement. The present paper is related to...
Article
Full-text available
This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na2SO4, Na2CO3, and Na2SiO3) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The...
Article
This paper discusses the effect of alkalis on strength development and hydration products in a commercial calcium sulfoaluminate clinker (KCSA). KCSA pastes were hydrated with water and 0.1 M, 1 M, 2 M, 4 M and 8 M NaOH. The hydration products were characterised at 3d, 28d and 90d, by XRD, SEM, DTA/TG and ²⁷Al MAS-NMR. With 0.1 M, 1 M and 2 M, the...
Article
This study aimed primarily to broaden the limited knowledge presently at hand about ternesite, 5CaO·2SiO2·SO3 (shorthand C5S2S¯,ter), reactivity in calcium sulfoaluminate-calcium aluminate (CSA-CAC) blended cements by exploring the hydration of the constituents of simplified CaO·Al2O3 (CA)+5CaO·2SiO2·SO3 (ter)+CaSO4∙2H2O (gypsum, gyp) or 12CaO·7Al2...
Article
Full-text available
This paper reports an Alkali-Activated Materials (AAM) using two different precursors, metakaolin and a metallurgical slag with photocatalytic zinc oxide nanoparticles, as novel photocatalytic composites. The photodegradation performance of the composites using methylene blue (MB) dye as a wastewater model was investigated by ultraviolet radiations...
Article
Full-text available
Due to the increase of water consumption, water treatment systems become more actual and innovative materials for water treatment are welcomed. Traditionally, alkalizing agents, such as lime or caustic soda, have been employed to increase the pH levels, which induce chemical clarification of wastewater. Some innovative ideas of using low-calcium, a...
Article
This study was designed to determine the mineralogical and microstructural changes taking place in a hybrid alkaline cement (HYC = 30% Portland cement clinker + 70% (slag + fly ash + alkaline activator)) exposed to high temperatures. The cement pastes were heated for 2 h at 400 °C, 600 °C, 800 °C or 1000 °C and subsequently air- or water-cooled. Th...
Article
Alkaline (or geopolymer) cements have proven to be a sustainable alternative to the ordinary portland cement material. The laboratory reagents normally used as alkaline activators constitute the most costly and on occasion polluting constituents of such cementitious systems. This study aimed to explore the use of a disposed cleaning solution (CS),...
Article
Steel-making slags, resulting from basic oxygen furnaces or electric arc furnaces are heavily applied in the construction industry, as an aggregate for pavements or concrete. Although possessing a significant crystalline content, it is expected that, if properly milled, the reactivity of these slags can increase up to a point when they are viable t...
Article
This study explored the effect of adding 10% of finely ground limestone dust to alkaline hybrid cements. A series of binders was prepared with 20–30% OPC (CEM I 52.5R) and fly ash in the presence or absence of a chemical activator (5% Na2SO4). The rate of heat release was determined by isothermal conduction calorimetry. Setting times and 3 d, 28 d...
Article
Full-text available
The present study explores the effect of activating solution concentration (4, 6 and 8 M NaOH) on mechanically and thermally pre-treated carbonate-high illite clay (LCR). Pastes were prepared with an alkaline solution/clay (S/B) ratio of 0.55, which were cured at room temperature and relative humidity > 90% in a climatic chamber. At two and 28 days...
Article
Full-text available
Mine tailings (MT) could represent a step forward in terms of the quality of the aggregates usually used in civil engineering applications, mostly due to its high density. The Portuguese Neves Corvo copper mine, owned by the Lundin Mining Corporation, produces approximately 3 million tonnes per year. Nevertheless, it cannot be used in its original...
Article
Full-text available
The high-temperature mechanical behaviour of a pre-industrial hybrid alkaline cement (HYC) was studied. The HYC in question contained 30 % Portland clinker and 70 % of a blend of slag, fly ash and a solid activator (mix of alkaline salts with a predominance of Na2SO4). The material was tested during exposure to high temperatures to establish its co...
Article
The behavior of sulfoaluminate (CSA) cements hydrated in neutral or alkaline solutions (0 M, 0.1 M, 1 M, 4 M and 8 M NaOH) was studied. 2-d, 28-d and 90-d mechanical strengths were determined, as well as the reaction rate by isothermal conduction calorimetry. The reaction products were characterised with XRD, DTA and SEM. The findings revealed diff...
Conference Paper
This study aimed to determine the physical, mechanical, mineral and microstructural properties of a industrially manufactured hybrid cement (HYP), consisting 47,5 % Belite clinker + 47,5 % FA + 5 % solid alkaline activator. The effect of the curing temperature (25ºC, or 85 ºC) on hydration kinetics and on compressive strength development (in paste...
Article
An increasing interest in the development of alternative solutions based on the use of wastes and residues in the context of soft soils improvement has been observed in the last few years. Most of such research is related to the laboratory characterization of the soil-binder or soil-reinforcement mixtures. However, the viability and impact of the c...
Article
During the present work, different binders were synthetized by alkaline activation of fly ash (FA) and a mixture of 75% fly ash and 25% metallurgical slag (FASLG). Two different curing periods, of 7 and 28 days, were considered. A Variance Analysis (ANOVA), conducted to assess the effectiveness of the Response Surface Methodology that was used to s...
Article
Full-text available
The mechanical performance of a hybrid cement containing 48% fly ash, 48% mineralized belite clinker, 1. 5% gypsum and 2.5% Na2SO4 was analyzed and the hydration products were identified. The findings showed that the newly designed cement met European standard EN 197-1 compositional, mechanical and setting time requirements (cement type IVB). The h...
Article
Full-text available
This paper is wholly committed to resource efficiency through the valorization of waste from other industries, and more specifically fly ash as a raw material to produce concrete-like geopolymers. In particular, this study aimed to determine the effect of the physical and chemical characteristics of recycled coal fly ash used to manufacture alkalin...
Article
The present paper addresses the feasibility of using an iron and steel slag aggregate (ISS), resulting from electric arc furnace, as a recycled raw material in the production of a new concept of mortar composite, based on alkaline activation, designated as ‘alkali activated composite’ (AACO). The original ISS aggregate was used both as a precursor...
Article
Introduction of new residues and wastes in the development of alkaline activated materials is a majorconcern regarding the spreading and dissemination of this technique. Such increase in the spectrum ofavailable raw materials will decrease the need for long-distance transportation of the more traditionalprecursors that have been tirelessly used in...
Article
Full-text available
Mine tailings could represent a step forward in terms of the quality of the aggregates that usually accepted in civil engineering applications, due to their specific weight and compressive strength. The Neves-Corvo copper mine produces approximately 3 million tons of tailings every year, which could supply several construction works, at least in th...
Article
The present study aimed to determine the rheological behavior of activated phosphorus slag (AAPS) with a combination of Ca(OH)2 and Na2CO3 (CNC activator) or Na2SO4 (CNS activator) compared to OPC paste. The findings showed that the rheology of AAPS pastes fit with the Herschel-Bulkley model and behaved like a shear-thinning fluid. The AAPS pastes...
Article
‘Portland-alkaline’ hybrid cements (HYC), the latest generation of alkaline cements, are multi-component systems consisting in blends with high mineral addition and low portland cement contents. In the presence of alkaline activators, these systems set and harden into materials with excellent cementitious properties. This study explored the 2 and 2...
Article
In this study fly ash contents of up to 50 % were used to produce binders with mechanical strength greater than or equal to type CEM I 42.5R cement (reference). The specific aim pursued in this research was to determine whether the procedure used to add the chemical activator (in solid or liquid form) can affect strength development in the cement o...
Article
This work aims at investigating the possibility of reusing sludge from sandstone sawing in alkaline cements. In particular, the behaviour towards alkali activation process of Pietra Serena sludge (sPS), either alone or in binary mixtures with class F fly ashes and metakaolin, was evaluated. The binders were synthesised with 8 M and 12 M NaOH soluti...
Article
This paper deals with the stabilisation of the fines portion of Construction and Demolition Waste (CDW) produced by a Portuguese recycling company. The recycled aggregate was analysed with and without the addition of a well-known precursor – fly ash (FA), considering different CDW/FA weight ratios. The resulting mixtures were activated with a solut...
Article
Full-text available
Moderately alkaline activators can be used to formulate cementitious binders with a high Supplemetary Cementitious Materials (SCMs) and a low portland cement content (hybrid alkaline cements). This study aimed to prepare hybrid alkaline cements containing large percentages of dehydroxylated bentonite (BT) and small Portland cement (OPC) fractions,...
Article
The use of industrial by-products to produce new types of cement-substitute binders is gaining significant momentum, especially through the alkaline activation technique. However, the exact curing conditions that should be considered with each binder variation have not yet been fully understood. The aim of the present work is thus the statistical a...
Article
The primary object of the present research was to investigate the porous low calcium alkali activated material (AAM). Traditionally Na+ ions for alkali activation solution ensure highly alkaline media which enhances the dissolution of amorphous phase in the raw materials forming solid cementitious material with sodium aluminosilicate hydrate (N-A-S...
Article
Full-text available
This paper proposes an alternative use for waste such as the ash generated by coal-fired power plants and municipal incineration facilities, specifically as a raw material in alkali-activated hybrid cements. The proposal was tested by preparing a series of hybrid cements with blends of fly ash (FA) and clinker (CK) or municipal solid waste incinera...
Article
Full-text available
The aim of the present paper is to analyse the potential application of a solution used to wash moulds from the aluminium casting industry as an alkali activator, for inclusion in the production of alkaline cement. To evaluate the effectiveness of this cleaning solution (CS), two different by-products / wastes were considered as a precursor: fly as...
Article
Full-text available
This study analyses the behavior of calcium silicates C3S and C2S hydrated in two alkaline media, Na2CO3 and Na2SO4. The silicates were synthesized with laboratory reagents and hydrated in water, to which solid-state alkaline activators with 4 wt% Na2CO3 or 4 wt% Na2SO4 were added. Two- and 28-day mechanical strength values were determined and the...
Article
Full-text available
In hybrid alkaline fly ash cements, a new generation of binders, hydration, is characterized by features found in both ordinary portland cement (OPC) hydration and the alkali activation of fly ash (AAFA). Hybrid alkaline fly ash cements typically have a high fly ash (70 wt % to 80 wt %) and low clinker (20 wt % to 30 wt %) content. The clinker comp...
Article
This study aimed to determine the physical-mechanical, mineralogical and microstructural properties of a pre-industrially manufactured hybrid cement (HYC) containing 5% alkaline activator and less than 30% clinker. The effect of the initial curing temperature (25 ± 1 or 85 °C for 20 h) on hydration kinetics and the development of compressive streng...
Article
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 Na2O (8 wt. %) as a fluxing oxide. The effect of including small amounts of...
Article
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 uni...
Article
Full-text available
This paper focus on evaluating the ability to use Mexican fly ash (FA) and copper slag (CS) to produce alkali cements (0% OPC) or hybrid cements (20% OPC + 80% fly ash). The alkali activators used were two: 8 M NaOH solution for alkali cements and NaCl with sodium silicate for hybrid cement (HYC). Results of mechanical testing and characterization...
Article
Coal fly ash can be subject to large variations in characteristics as a function of the type of coal burned, the operation status of the coal power plant and the ash separation technology employed. Good quality fly ash is in demand in the cement industry (and in the concrete plants) due to its ability to partially substitute some Portland cement (t...
Chapter
Alkaline cements consist essentially of two components: a cementitious material and an alkaline activator. Natural materials (metakaolin) or industrial by-products (such as slag and fly ash) with amorphous or vitreous structures are used as cementitious components, while the liquid or solid alkaline activators applied are generally alkaline salts o...
Chapter
Full-text available
This chapter reviews the physical-chemical principles governing alkali-activation processes in both high- and low-CaO aluminosilicate materials. It addresses factors such as starting material composition, reaction mechanisms, and the nature, composition and structure of the reaction products. Models describing the microstructure of the materials an...
Article
Full-text available
The alkaline activation of aluminosiliceous industrial by-products such as blast furnace slag and fly ash is widely known to yield binders whose properties make them comparable to or even stronger and more durable than ordinary Portland cement. The present paper discusses activation fundamentals (such as the type and concentration of alkaline activ...
Article
Full-text available
Hybrid alkaline cements are multi-component systems containing a high percentage of mineral additions (fly ash, blast furnace slag), low proportions (<30%) of Portland clinker and scarce amounts of alkaline activators. The substantially lower amount of clinker needed to manufacture these binders in comparison to ordinary Portland cement is both eco...
Conference Paper
The present study aimed primarily to determine the effect of particle size distribution and the chemical and mineralogical composition of different types of Chinese fly ash on the nature of the reaction products resulting from the alkaline activation of those materials and on mechanical strength development in the hardened pastes. Three type F (AST...
Conference Paper
This paper reports on a comparative study of the mechanical performance at high temperatures of a commercial Portland cement (CEM I 42.5 (OPC)), a hybrid cement (CEM HYC = 30% clinker + 32.5 % BFS + 32.55 % FA + 5 % alkaline activator) and a geopolymer (fly ash-activated with waterglass solution). Two types of mechanical tests were conducted on sam...
Article
This study analyzed the behavior of two laboratory-synthesized calcium silicates, C 3 S and C 2 S, after hydration in 8-M NaOH and in water as a control. Two-and 28-d mechanical strength values were determined and the products were characterized with XRD, TEM, and 29 Si and 23 Na MAS NMR. The results showed that hydrating C 3 S in a highly alkaline...
Article
Full-text available
A model for alkaline activation has recently been designed to develop new cementitious systems known as hybrid alkaline cements. These multi-component systems contain a high percentage of mineral additions (fly ashes, slags (BFS), metakaolin (MK), bentonites (BT) …), low proportions (29Si and 27Al NMR. Both systems developed high mechanical strengt...
Article
Full-text available
The environmental problems posed by Portland cement manufacture have prompted the scientific committee to seek more eco-efficient binders with the same technological features as OPC; hybrid cements are among such alternative materials. Hybrid alkaline cements are multi-component systems containing a high mineral addition (fly ash (FA), metakaolin (...
Chapter
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 co...
Article
Full-text available
For many years now the idea of including alkalis in a Portland cement matrix has been regarded as a daft or inexcusably erroneous proposition: despite its absurdity, that opinion has been widely accepted as a basic premise by the scientific and technical community working in the area of the chemistry of cement. In 1957 Glukhovsky proposed a working...
Conference Paper
Full-text available
This paper discusses a study conducted on reactivity in ordinary blast furnace (BFS) and ferronickel (Fe-Ni-S) slag to appraise their possible use as cement. Both materials were alkali-activated in the traditional manner (alkaline cements, AC) and in the presence of 45 % clinker (hybrid cements, HYC). The ACs were prepared with an alkaline solution...
Article
This study aims to advance in the understanding of how alkaline concentration and temperature affect metakaolin dissolution and hydrolysis and the characteristics of the reaction products formed. Two working temperatures, 25 and 85 °C, and two alkaline concentrations, 5- and 8-M NaOH, were studied. The findings showed that metakaolin dissolution is...
Article
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 reactivit...
Article
Full-text available
Hybrid alkaline cements are obtained by alkali-activating cementitious blends in the Na2O-CaO-SiO2-Al2O3-H2O system. The present paper discusses the results of activating different cementitious blends containing a low OPC clinker content (<30%) and a high content of supplementary cementitious materials (such as Fly ash). To obtain useful early mech...