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De Pablo L.,National Autonomous University of Mexico | Doval M.,Complutense University of Madrid | Iglesia A.L.,Complutense University of Madrid | Soriano J.,Laboratorio Central Of Estructuras Y Materiales Cedex
Revista Mexicana de Ciencias Geologicas | Year: 2014

This paper presents the occurrence, mineralogy and process of formation of CaK-clinoptilolite, KNa-chabazite, KNa-heulandite, KNa-erionite and Na-phillipsite in pyroclastic rocks from the Calvillo-Jalpa-Nochixtlán area in the Province of the Mesa Central, Mexico. CaK-clinoptilolite, (Si30.600-30.150Al5.760-5.220)(Ca1.890-1.800K1.080-0.810Mg0.540-0.450) O72, of 5.04-5.86 Si/Al, 0.83-0.86 Si/(Si+Al) and 0.26-0.31 (Na+K)/ (Na+K+Ca+Mg) ratios, free of Na, crystallized from siliceous alkaline pore fluids and glasses of composition (Si0.890-0.825Al0.202-0.102)(K0.072-0.020Ca0.020-0.010Fe0.050-0.010)O2 in tuffaceous rocks northeast of Jalpa. KNaheulandite, (Si28.080Al8.010)(K4.680Na2.250Ca0.270Fe0.180)O72, KNa-chabazite, (Si9.210-9.000Al3.090-2.940)(K0.750-1.180Na0.360-1.260Ca0.150-0.030Fe0.210-0.090Mg0.380-0.210) O24, NaK-erionite, (Si27.990Al7.830)(K2.000)(K4.210Na1.620Ca0.090Fe0.090Mg0.180)O72, and Na-phillipsite, (Si12.080Al3.920)(Na3.160K0.240Ca0.160Fe0.040) O32, of 2.91-3.57 Si/Al, 0.74-0.78 Si/(Si+Al) and 0.72-0.97 (Na+K)/ (Na+K+Ca+Mg) ratios, dominant exchange cations K and Na, formed from siliceous alkaline high-pH fluids and glasses of composition (Si0.910-0.833Al0.170-0.092)(K0.101-0.050Na0-0.033-0.027)O2 in tuffs northwest of Nochixtlán. The zeolites were formed in the Jalpa area by diagenetic alteration of the tuff; in the Nochixtlán area, enrichment of Na and formation of alkali-rich zeolites was attributed to alkaline saline brines in an open hydrologic system. They occur in Oligocene - early Miocene tuffaceous rocks associated to the volcanism of the Sierra Madre Occidental, exposed in the Calvillo-Jalpa-Nochixtlán area in the states of Aguascalientes and Zacatecas, in the Province of the Mesa Central, Mexico. Source


De Pablo Galan L.,National Autonomous University of Mexico | Doval M.,Complutense University of Madrid | La Iglesia A.,Complutense University of Madrid | Soriano J.,Laboratorio Central Of Estructuras Y Materiales Cedex | Chavez L.,National Autonomous University of Mexico
American Mineralogist | Year: 2013

Cristobalite-tridymite blade nanocrystals cemented by SiO2-glass and tridymite nanocrystals fill separately SiO2-glass spherules released by explosive volcanism, in rhyolitic tuffs from the Province of the Mesa Central, Mexico. This paper presents the mineralogy of silica polymorphs, occurrence, and process of formation in the Province of the Mesa Central. The understanding of the origin of these pure SiO2-polymorphs, their association with high-temperature minerals, fractionation of magmas, and role of volatiles contribute to our knowledge on silica minerals, their technological implications and damaging health effects. Results indicate that a precursor magma, from which kyanite crystallized, partitioned into an immiscible Fe-rich magmatic liquid that crystallized Fe-cordierite, Fe-amphiboles, and fayalite and into a siliceous melt that led to low-temperature glasses of 78.22-80.01 wt% SiO2 and Si/Al ratio 4.07-5.65. Presence of amphiboles, sulfur in cristobalite-tridymite crystals and alunite suggest association of volatiles. The crystallization of silica polymorphs is associated with the dissolution of water vapor and volatiles in the precursor magma, establishing a silicate melt-water system of two critical points, one of them at pressure and temperature near the critical point of water and another close to the critical point of SiO2, and defining a critical curve between them and supercriticality at pressures and temperatures lower than the critical point of SiO2. Decreasing the ambient conditions from supercritical to subcritical would have allowed the separation of liquid and gases and the crystallization of cristobalite-tridymite and tridymite nanocrystals from the vapor phase. Cristobalite single crystals were not formed and transformation of cristobalite and trydimite to quartz did not occur. We conclude that glasses did not crystallize cristobalite or tridymite. Components in excess of the pure phases precipitated as nanoparticles of siliceous glass forming agglomerates, some containing iron hydroxides and alunogen. Source


Noval A.M.,Laboratorio Central Of Estructuras Y Materiales Cedex | Blanco M.,Laboratorio Central Of Estructuras Y Materiales Cedex | Castillo F.,Laboratorio Central Of Estructuras Y Materiales Cedex | Leiro A.,Laboratorio Central Of Estructuras Y Materiales Cedex | And 5 more authors.
10th International Conference on Geosynthetics, ICG 2014 | Year: 2014

The Barranco de Benijos reservoir (Canary Islands, northern hemisphere) is waterproofed with a reinforced PVC geomembrane. The paper presents the results of a study of the influence of orientation on the ageing of the geomembrane based on tests conducted on samples from the north slope and the south slope of the reservoir up to 26 years after geomembrane installation. Data on the evolution of the following properties are presented: Plasticizer content, thicknesses, foldability at low temperature, tensile properties, dynamic and static puncture, and seam strength. Furthermore, microanalyses were performed using: reflection optical microscopy, scanning electron microscopy and X-Ray. The results obtained show significant differences between north and south samples. From these results, it is estimated that the PVC geomembrane deterioration was 1.2 to 1.25 times faster on the north slope than on the south slope. The study also shows that the end of the service life of the considered reinforced PVC geomembrane can be expected at a plasticizer content of 15% or less. Source


Noval A.M.,Laboratorio Central Of Estructuras Y Materiales Cedex | Blanco M.,Laboratorio Central Of Estructuras Y Materiales Cedex | Castillo F.,Laboratorio Central Of Estructuras Y Materiales Cedex | Leiro A.,Laboratorio Central Of Estructuras Y Materiales Cedex | And 5 more authors.
10th International Conference on Geosynthetics, ICG 2014 | Year: 2014

The long-term performance of the high density polyethylene geomembrane used as waterproofing system of the "San Isidro" reservoir (Canary Islands, Spain) is described in this paper. The geomembrane characteristics and its behaviour with time are evaluated. This includes interpretation of tests to quantify the geomembrane thicknesses, tensile properties, tear resistance, dynamic and static puncture, foldability at low temperature, and seam strength. In addition, microscopy techniques, X-rays microanalysis, carbon black, crystallinity, density and oxidation induction time tests were carried out. Overall, the long-term test results indicate a very good performance of exposed HDPE geomembrane installed at a subtropical climate location. Source


Thomas C.,University of Cantabria | Setien J.,University of Cantabria | Polanco J.A.,University of Cantabria | Alaejos P.,Laboratorio Central Of Estructuras Y Materiales Cedex | Sanchez De Juan M.,Laboratorio Central Of Estructuras Y Materiales Cedex
Construction and Building Materials | Year: 2013

This paper presents the main results of the research carried out to analyse the physical, mechanical and durability properties of concrete incorporating recycled aggregate. One of the most unknown aspects of recycled aggregate concretes is related to their durability in aggressive environments. Also most of the results found in the literature are not comparable due to the heterogeneity of the recycled aggregates, water/cement ratios and types of cement used. In this research, recycled aggregate concrete with partial and total coarse aggregate replacement and reference concretes with 24 water/cement ratios have been cast to study their physical and mechanical properties, behaviour under accelerated carbonation, water and oxygen permeability. The results show, for the same w/c ratio, the influence of the recycled aggregate on the concretes. The durability of the concretes made with recycled aggregate is worse due to the intrinsic porosity of them. These differences decrease for low w/c ratios, as in this case the most influential factor is the low porosity obtained in the new improved cement paste. Considering the mechanical properties, the influence of the recycled aggregate is worse for the high w/c ratios. On the basis of the results obtained, recommendable mixtures for recycled aggregates in aggressive environments will be suggested. Also, an experimental model from the recycled aggregate concretes compressive strength is proposed. © 2012 Elsevier Ltd. All rights reserved. Source

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