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Turner S.,IECA
IEEE Internet Computing | Year: 2014

Transport Layer Security is the standard, widely deployed protocol for securing client-server communications over the Internet. TLS is designed to prevent eavesdropping, tampering, and message forgery for client-server applications. Here, the author looks at the collection of standards that make up TLS, including its history, protocol, and future. © 2014 IEEE. Source


Andrade C.,IETCC CSIC | D'Andrea R.,IECA
2nd International Conference on Sustainable Construction Materials and Technologies | Year: 2010

Current codes have requirements for the durability design of concrete based on compressive strength and provisions related to cement content and water - cement ratio. However, such requirements do not take into account important parameters related to the behaviour of concrete against to aggressive attack. The electrical resistivity of the hardened concrete is related to connectivity of pores network under saturated condition. This paper proposes a methodology of design based on the Archie law, which is originated from the concept of diffusion and provides properties such as electrical resistivity, porosity, and tortuosity, for estimating the ideal mix of concrete (maximum water cement, the minimum content of cement and cement type) for a specific environmental class and service life. It also considers the chemical reaction of chloride and carbonation with the phases of cement, so called factor of reaction (r) which depends on the type of cement and indicates the delay on the agressive penetration. Source


Galan I.,CSIC - Eduardo Torroja Institute for Construction Science | Andrade C.,CSIC - Eduardo Torroja Institute for Construction Science | Mora P.,Oficemen | Sanjuan M.A.,IECA
Environmental Science and Technology | Year: 2010

Carbonation of reinforced concrete is one of the causes of corrosion, but it is also a way to sequester CO2. The characteristics of the concrete cover should ensure alkaline protection for the steel bars but should also be able to combine CO2 to a certain depth. This work attempts to advance the knowledge of the carbon footprint of cement. As it is one of the most commonly used materials worldwide, it is very important to assess its impact on the environment. In order to quantify the capacity of cement based materials to combine CO2 by means of the reaction with hydrated phases to produce calcium carbonate, Thermogravimetry and the phenolphthalein indicator have been used to characterize several cement pastes and concretes exposed to different environments. The combined effect of the main variables involved in this process is discussed. The moisture content of the concrete seems to be the most influential parameter. © 2010 American Chemical Society. Source


Argiz C.,CSIC - Eduardo Torroja Institute for Construction Science | Menendez E.,CSIC - Eduardo Torroja Institute for Construction Science | Moragues A.,Technical University of Madrid | SanjuAn M.A.,IECA
Structural Engineering International: Journal of the International Association for Bridge and Structural Engineering (IABSE) | Year: 2014

New additions to cement will help to obtain sustainable and durable construction materials. One of these new Portland cement constituents could be coal bottom ash. Currently, it is dumped as waste, provoking an environmental problem. However, shows how this material can be used as the main constituent of Portland cement when it is mixed in an optimized proportion with fly ash. Therefore, this study may also be considered as a pre-standardization work to meet, partially, an environmental demand of society. The compressive strength and durable characteristics of standardized mortars made of coal combustion bottom and fly ash are to mortars made of CEM I 42,5 N according to the European standard EN 197-1:2011, which is used as reference. The mortars made up of bottom ash, fly ash and ordinary Portland cement mixes have similar proportions to the standardized ones for CEM II/A-V, CEM II/B-V and CEM IV/A (V) cements. It was concluded that the utilization of bottom ash mixed with fly ash does not modify the compressive strength or durable characteristics of the mortars studied in this research program. Source


Galan I.,CSIC - Eduardo Torroja Institute for Construction Science | Andrade C.,CSIC - Eduardo Torroja Institute for Construction Science | Mora P.,Oficemen | Sanjuan M.A.,IECA | And 2 more authors.
2nd International Conference on Sustainable Construction Materials and Technologies | Year: 2010

Although carbonation of cement phases is well known, the amount of carbon dioxide combined during the process has been much less investigated. Related to the greenhouse effect much more attention is being paid to the sinks for CO 2 in order to correctly compute the gases emission during production of materials. In the case of cement a strict calculation should discount the CO 2emitted from that fixed by the concrete. This is the aim of present work which is a study of the cement based materials ability to combine CO 2. Using Thermogravimetry and Differential Thermal Analysis as well as phenolphthalein indicator, quantities of CO 2 combined and carbonation depth in several cement pastes and concretes exposed to different environments have been measured. A calculation to estimate the contribution of cement based materials carbonation to the partial re-absorption of the CO2 emitted in cement production is proposed. Source

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