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Tomás Vázquez

Bio: Tomás Vázquez is an academic researcher from Spanish National Research Council. The author has contributed to research in topics: Cement & Portland cement. The author has an hindex of 17, co-authored 60 publications receiving 2068 citations.


Papers
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TL;DR: The activation of fly ash/slag pastes with NaOH solutions has been studied in this paper, where the authors established the equations of the models describing the mechanical behaviour of these pastes as a function of the factors and levels considered.

745 citations

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TL;DR: In this article, the results of a research project initiated to study the stability of these materials when exposed to aggressive solutions were presented, where prisms of mortar made of sand and alkali-activated metakaolin were immersed in deionized water, ASTM sea water, sodium sulfate solution (4.4% wt), and sulfuric acid solution (0.001 M).

510 citations

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TL;DR: In this paper, three different matrices were used: (a) granulated blast furnace slag activated with waterglass (Na2SiO3+NaOH) with a concentration of 4% Na2O by mass of slag and cured at room temperature, (b) aluminosilicate fly ash activated with 8M NaOH and cured with 85 °C during the first 24 h and (c) 50% fly ash+50% slag activation with 8m NaOH solution at room-temperature.

289 citations

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TL;DR: In this paper, the behavior of waterglass- or NaOH-activated slag mortars after carbonation was analyzed and the effect of a superplasticizer based on vinyl copolymer and shrinkage reducing polypropylenglycol derivative admixtures on that process was examined.
Abstract: This study analyzes the behaviour of waterglass- or NaOH-activated slag mortars after carbonation. The effect of a superplasticizer based on vinyl copolymer and shrinkage reducing polypropylenglycol derivative admixtures on that process was also examined. The same tests were run on cement mortars for reference purposes. The mortars were carbonated in a chamber ensuring CO2 saturation for four and eight months, after which ages the samples were tested for mechanical strength; mercury porosimetry and mineralogical (XRD, FTIR) and microstructural characterization (SEM/EDX) were also conducted. The results obtained indicate that alkali-activated slag mortars were more intensely and deeply carbonated than Portland cement mortars. Carbonation took place directly on the gel, causing decalcification. When waterglass was the alkaline activator used, carbonation caused a loss of cohesion in the matrix and an important increase in porosity and decrease in mechanical strength. When a NaOH solution was used as the alkali activator, carbonation enhanced mortar compaction and increased mechanical strength. Finally, in waterglass-activated slag mortars, the inclusion of organic admixtures had no effect either on their behaviour after carbonation or the nature of the reaction products.

248 citations

Journal ArticleDOI
TL;DR: In this paper, the alkali-silica reaction in waterglass-alkali-activated slag (waterglass-AAS) and ordinary Portland cement (OPC) mortars was evaluated using three types of (siliceous and calcareous) aggregates.
Abstract: The alkali–silica reaction in waterglass-alkali-activated slag (waterglass-AAS) and ordinary Portland cement (OPC) mortars was evaluated using three types of (siliceous and calcareous) aggregates. The tests were conducted to the ASTM C1260-94 standard test method. The mortars were studied by volume stability, mechanical strength and Hg intrusion porosity. The ASR products were studied with XRD, FTIR and SEM/EDX techniques. According to the results obtained, under the test conditions applied in this study, waterglass-AAS mortars are stronger and more resistant to alkali-aggregate reactions than OPC mortars. When the mortars were made with a reactive siliceous aggregate, expansion was four times greater in the OPC than in the AAS material. When a reactive calcareous (dolomite) aggregate was used, no expansion was detected in any of the mortars after 14 days, although the characterization results showed that the dolomite had reacted and calcareous-alkali products (brucite) had in fact formed in both mortars. These reactive processes were more intense in OPC than in AAS mortars, probably due to the absence of portlandite in the latter. When the calcareous aggregate was non-reactive, no expansions were observed in any of the mortars, although a substantial rise was recorded in the mechanical strength of AAS mortars exposed to the most aggressive conditions (1 M NaOH and 80 °C).

80 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the mechanism of activation of fly ash with highly alkaline solutions is described, and the product of the reaction is an amorphous aluminosilicate gel having a structure similar to that of zeolitic precursors.

1,779 citations

Journal ArticleDOI
TL;DR: In this paper, the potential position of and drivers for inorganic polymers (“geopolymers”) as an element of the push for a sustainable concrete industry are discussed.

1,444 citations

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TL;DR: In this paper, a mechanistic model accounting for reduced structural reorganization and densification in the microstructure of geopolymer gels with high concentrations of soluble silicon in the activating solution has been proposed.

1,309 citations

Journal ArticleDOI
TL;DR: Aluminosilicate-based alkaline cements have been classified into five categories as discussed by the authors, and the key advances made in the understanding of synthetic gels are discussed, which ultimately finds hybrid cements to be technologically viable materials for contemporary construction.

1,104 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization, and demonstrate that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymers.
Abstract: Geopolymerization is a developing field of research for utilizing solid waste and by-products. It provides a mature and cost-effective solution to many problems where hazardous residue has to be treated and stored under critical environmental conditions. Geopolymer involves the silicates and aluminates of by-products to undergo process of geopolymerization. It is environmentally friendly and need moderate energy to produce. This review presents the work carried out on the chemical reaction, the source materials, and the factor affecting geopolymerization. Literature demonstrates that certain mix compositions and reaction conditions such as Al2O3/SiO2, alkali concentration, curing temperature with curing time, water/solid ratio and pH significantly influences the formation and properties of a geopolymer. It is utilized to manufacture precast structures and non-structural elements, concrete pavements, concrete products and immobilization of toxic metal bearing waste that are resistant to heat and aggressive environment. Geopolymers gain 70% of the final strength in first 3–4 h of curing.

1,078 citations