Mechanische Hochtemperatureigenschaften von flugaschebasierten Geopolymerbetonen

Mechanical properties of fly ash‐based geopolymer concretes at high temperature At present, concretes based on alkali‐activated binders, so‐called geopolymer concretes, are investigated intensively in the building materials industry and by the research community as environmentally friendly alternative to Portland cement‐based concretes. These inorganic binders, which are based on industrial by‐products such as fly ash and ground granulated blast furnace slag, exhibit high resistance against corrosive acids and salts, if properly designed. The mechanical properties of fly ash‐based geopolymer concretes at high temperatures are subject of systematic investigations at the Bundesanstalt für Materialforschung und ‐prüfung (BAM) to create a basis for the structural design of fire exposed concrete members based on alkali‐activated binders. The concrete specimens, produced with quartz aggregates or lightweight aggregates and heated to a maximum temperature of 750 °C, exhibited a decrease of compressive strength up to temperatures of ca. 300 °C, attributed to formation of microcracks caused by dehydration. At higher temperatures the compressive strength of the investigated geopolymer concretes recovered partly, due to sintering processes starting from ca. 500 °C. Because of this beneficial property when compared to conventional concretes, geopolymer concretes can potentially be applied in infrastructure facilities where fire resistance is critical. From the results of the thermomechanical tests stress‐strain relationships are derived that can be used for the structural design of members made from geopolymer concretes.     

Structural fire design parameters and procedures – analysis of the potential of Eurocode 3

This paper presents an experimental research carried out for testing the simple calculation models presented in EN 1993‐1‐2 for the determination of the fire resistance of steel structures, as well as the models for calculating the development of temperature in the structure. The analysis was carried out for the simple heat transfer models in protected and unprotected steel elements, for the basic parameters of reduction of mechanical properties of steel at high temperatures, and for simple calculation models for determining fire resistance of elements subjected to vertical force in combination with and without the action of the axial force.     

Verification of the fire resistance of clay brick masonry – hints for efficient design

In Germany, structural fire design of masonry is carried out in a simplified way using tabulated minimum wall thicknesses depending on the loading level in fire. Against this background the procedure of structural fire design is shown briefly before two approaches for a more efficient verification of the fire resistance are explained. The first possibility is to determine the reduction factor for the design value of the actions in fire more precisely and thereby reduce the loading level. Secondly, a design methodology is presented which can be applied in case of masonry walls with low vertical load but a large load eccentricity at mid‐height of the wall. Finally, the verification of the fire resistance of masonry according to national technical approval is discussed with an explanation how to obtain the same loading level in fire if the design is based on DIN EN 1996‐3/NA as when it is based on DIN EN 1996‐1‐1/NA.