Durabilidad del hormigón. I. Resistencia química de los cementos
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Cementos puzolánicos
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Extractos de revistas técnicas
Acción del CO2 sobre un cemento portland. I. Influencia sobre los características químicas y fisicomecánicas
El efecto que el dióxido de carbono produce sobre los compuestos anhidros e hidratados del cemento portland ha sido objeto de estudio por numerosos investigadores, debido a la influencia que ejerce en las propiedades de los conglomerados correspondientes. La reacción de carbonatación del cemento portland lleva consigo…
Determinación electroquímica cuantitativa de la velocidad de corrosión de un acero de construcción. Evaluación de la susceptibilidad al ataque por picaduras. Parte I: Ensayos en disolución saturada de hidróxido cálcico
En un trabajo anterior (1) se analizaron las distintas características de los métodos electroquímicos empleados hasta la actualidad para la detección del ataque localizado en el caso de un acero de construcción sumergido en disolución saturada de hidróxido cálcico, así como el efecto despasivante e inhibidor que sobre…
EFFECT OF pH ON PHOSPHATE ADSORPTION AND ISOTOPIC EXCHANGE IN ACID SOILS AT LOW AND HIGH ADDITIONS OF SOLUBLE PHOSPHATE
Summary Measurements of equilibrium phosphate concentrations, adsorbed phosphate and isotopically exchangeable phosphate (E t ) were made on suspensions of acid soils at initial P concentrations ranging from 1–1000 μM and pH values between 4.2 and 6.8. At low P concentrations (1–100 μM), the affinity of the adsorption…
Tritium Diffusion in A1 2 O 3 and BeO
Tritium diffusion in aluminum and beryllium oxides was studied by recoiling tritium into specimens and measuring the time rate of tritium release during postirradiation heating. Results were consistent with classical diffusion solutions and gave single values for the diffusion activation energy over the temperature ra…
Magnetic anneal anisotropy in amorphous alloys
The uniaxial magnetic anisotropy Kuinduced by a magnetic anneal has been determined, after stress relief, for a series of alloys given by (FeyNi1-y)80B20. For all of these alloys Kudepends on anneal temperature as predicted by directional order theory. The concentration dependence of Kuin these alloys is also consiste…
High‐Temperature Mechanical Properties of Mullite Under Compression
The high strength potential of single‐phase mullite was investigated under compressive stress‐strain and creep testing conditions at 1400° and 1500°C. In single‐crystal experiments, no plastic deformation and, hence, no dislocation glide was observed. Polycrystalline mullite was deformed via the Nabarro‐Herring mechan…
Linear thermal expansion measurements on silicon from 6 to 340 K
Linear thermal expansion measurements have been carried out from 6 to 340 K on a high-purity silicon sample using a linear absolute capacitance dilatometer. The accuracy of the measurements varies from ±0.01×10−8 K−1 at the lowest temperatures to ±0.1×10−8 K−1 or 0.1%, whichever is greater, near room temperature, and…
Physical aging in plastics and other glassy materials
Abstract This paper surveys the basic aspects of physical aging. It shows that aging i s a general and important phenomenon found in all organic and inorganic glasses and in some metals as well. Moreover, the behavior of all these materials is very similar. It further shows that aging cannot be ignored in the testing…
Diffusion in polymer—solvent systems. I. Reexamination of the free‐volume theory
Abstract The free‐volume theory describing diffusion in polymer–solvent systems is reexamined. Calculation of the specific free volume for such systems is discussed, and equations are presented for the determination of the self‐diffusion coefficients of the polymer and the solvent. Conditions under which the mutual di…
Structural Peculiarities of Homo- and Co-polyurethanes
Recent advances in the investigation of polyurethanes are surveyed. Considerable attention is paid to copolyurethanes based on multicomponent initial constituents, which may exhibit thermoplastic or thermoelastoplastic properties depending on the distribution of the components in the chain and the length of the glycol…
Fine Structure of the Luminescence from Excitons and Multiexciton Complexes Bound to Acceptors in Si
My high-resolution studies of the bound-exciton luminescence in Ga-doped Si reveal a triplet structure. Also, I report for the first time bound multiexciton complexes associated with Ga, which are similar to those previously reported for Si doped with P, Li, and and B. In the case of Ga, however, the $m=2$ bound-multi…
On topographically identifiable sources of cathodoluminescence in natural diamonds
Abstract An extensive examination of the cathodoluminescent emissions from natural diamonds has been performed with due regard to their inhomogeneity, correlating cathodoluminescence properties point-by-point with the local crystal lattice texture and imperfection content as revealed by other topographic techniques (i…
Caprolactam based block copolymers using polymeric activators
Abstract Caprolactam has been polymerised by sodium hydride in the presence of isocyanate terminated polymers. The latter participate in the initiation reaction and allow the preparation of materials where the prepolymer can amount to 50% of the product. There is evidence that block copolymers are formed, and the prop…
The ratio of radial diffusion coefficient to mobility for electrons in helium, argon, air, methane and nitric oxide
The ratio of the radial diffusion coefficient to mobility D r / mu exp has been measured for the first time in five gases at high E/N (ratio of electric field to gas number density). The range of E/N was as follows: helium 3<or=E/N<or=847 Td; argon 8<or=E/N<or=1271 Td; air 14<or=E/N<or=1412 Td; methane 14<or=E/N<or=56…
Effects of Chromium, Molybdenum and Vanadium on Spheroidization of Carbides in 0.8% Carbon Steel
Effecls of chro mium, moly'bdenum and vanadium on slJheroidi z alion of carbides in 0.8 0 a carbon sleel b)' slow cooling annealing have been invesligaled.
Effect of Boron on Transformation of Low-carbon Low-alloy Steels
The effect oj boron on the transformation oj 10w-carbon-!-mo!),bdCllum steels has been investigated by means oj dilatomelly and microstructural observations.The steels containing boron below 30 ppm exhibits the largest hardenability in the case oj austenitization at 930°C, but the hal-denability is reduced by austmiti…