4 results
Now showing1 - 4 of 4
- Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Moisture storage and transport in concrete: experimental investigations and computational modelingComprehensive insight on moisture transport in cement-based materials by means of experimental investigations and computer simulations Moisture Storage and Transport in Concrete explores how moisture moves through cementitious materials, focusing on its absorption, storage, and distribution with the help of experimental investigations and computer simulations. The text discusses the different ways moisture moves, such as through vapor or capillary action, as well as how it affects the properties of cement-based materials, offering new insights and models to help understand and predict moisture behavior in these materials, which can be important for construction and maintenance. After a short introduction to the topic, the text is split into five chapters. Chapter 1 covers surface energetic principles for moisture storage in porous materials. Chapter 2 explores real pore structure and calculation methods for composition parameters. Chapter 3 explains basic equations for the description of moisture transport. Chapter 4 discusses experimental investigation results with regard to the modeling of moisture transport in concrete materials. Chapter 5 showcases modeling of moisture transport, taking into account sorption hysteresis and time-dependent material changes. Written by a highly qualified author, Moisture Storage and Transport in Concrete also includes discussion on: • Dependence of surface energy of water on temperature, on relative humidity of air, and for aqueous salt solutions • Calculation of the pore size dependent distribution of inner surfaces using the moisture storage function • Temperature influence on the capillary transport coefficients and differences between capillary pressure and hydraulic external pressure • Adsorption and desorption isotherms of the CEMI reference material and causes of differences between adsorption and desorption isotherms • Sorption isotherms and scanning isotherms of hardened cement paste and concrete • Modeling of vapor transport and drying by evaporation of concrete Moisture Storage and Transport in Concrete is an essential reference to help researchers and professionals to make informed decisions for the construction of concrete-based infrastructure, enabling them to avoid common issues such as corrosion of reinforcement steel, deterioration of concrete strength, and the growth of mold and mildew.Publicationtype: Book32 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Limiting concentrations for ultra high strength concrete in contact with aggressive solutionsBased on the scientific literature and the results of the priority program “Sustainable Building with Ultra-High Performance Concrete” of the Deutsche Forschungsgemeinschaft (German Science Foundation) the German Committee for Structural Concrete is developing a guideline for Ultra High Strength Concrete (UHSC). One aspect is the durability in contact with aggressive solutions. The development of the guideline is an ongoing process. But some results can be presented, that will probably be accepted by the committee. Although it is widely accepted that UHSC has an increased durability, quantitative data usable within a concept of equivalent performance according to EN 206 are very rare, beginning with the simple question of acceptable damage depths. The contribution presents time dependent damage depths of several UHPC mixtures in contact with different acids and ammonium nitrate solution and other information about chemical attack. In addition the influences of non-static boundary conditions, curing and steel fibres are discussed. Allowed damage depths, measured with a normal strength reference mortar are shown. The results lead to the suggestion that UHSC in contact with aggressive solutions can be used up to the following limiting concentrations without additional protection. Ammonium solutions: 1000 mg/l NH4+, strong dissociated acids: pH 3.5, solutions with aggressive carbon dioxide: until saturation. A prerequisite of this limiting concentrations is that the high strength of the concrete is based on a very low water-cement-ratio and a particle packing optimization. To our opinion the limiting values for sulphate and magnesium solutions can not expanded at the moment, because the data base is too small. Additional research is needed in these cases.Publicationtype: Conference Paper249 299 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Evaluation of calcium hydroxide contents in pozzolanic cement pastes by a chemical extraction methodThe aim of the study is to investigate the calcium hydroxide (Ca(OH) 2) contents in pozzolanic cement pastes analyzed by the chemical extraction method and thermal analysis (DTA/TG). The second part of the study involves the carbonation of pozzolanic cement pastes and its influence on Ca(OH)2 reduction. The Ca(OH)2 contents in cement pastes after being subjected to accelerated carbonation were investigated by a chemical extraction method and compared to those values from DTA/TG analysis. The experimental results show that the chemical method reveals overall results comparable to those from DTA/TG analysis. However, in case of pastes containing high amounts of mineral admixtures or pastes subjected to carbonation which contain very low Ca(OH)2, only the chemical method yields precise reliable results by showing the pseudo-negative contents.Publicationtype: Journal Article6 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Zum Nachweis der Zugkraftdeckung biegebeanspruchter Stahlbetonbauteile mit nachträglich aufgeklebter Bewehrung(2004); ; Deutsches Institut für BautechnikDie neuen Verfahren zur Bemessung des Tragverhaltens von klebeverstärkten biegebeanspruchten Stahlbetonbauteilen ermöglichen eine genauere Beurteilung des wirklichen Verhaltens. Da das derzeitige Verfahren auf einen Endverankerungsnachweis mit zusätzlicher empirischer Dehnungsbegrenzung beschränkt ist und nicht in allen Fällen die für den Tragfähigkeitsnachweis maßgebende Querschnittslage erfasst und damit nicht in allen Fällen auf der sicheren Seite liegt, sollte zukünftig das "neue" Verfahren eingeführt werden. Auf die bisher übliche Begrenzung der Bruchdehnung und der sich daraus ergebenden beschränkten Ausnutzung der aufgeklebten Bewehrung sollte dann konsequenterweise verzichtet werden.Publicationtype: Technical Report604 259