This paper presents an experimental study on the development of material properties over time (up to around 2 years) and the structural behavior of reinforced beams, for two types of alkali-activated concrete (AAC). Compressive strength, flexural strength, tensile splitting strength, elastic modulus, and flexural behavior of reinforced beams are investigated. Tested material properties of AAC are compared with the properties of conventional concrete, as predicted by Eurocode. For the mixes of AAC and the conventional concretes with the same 28 days compressive strength, flexural and tensile splitting strength at 28 days are found to be similar, whereas the elastic moduli of AAC mixtures is up to 30% lower than those of conventional concrete. Related to the long term behavior, after 28 days moist-curing and subsequently exposing AAC specimens to laboratory conditions (50% RH/20°C), a reduction of flexural strength, tensile splitting strength and elastic modulus, is observed. Structural behavior of the reinforced AAC beams in four-point bending test seems not to be affected significantly by the observed decrease in material properties, and is found to be similar to that of conventional concrete beams. The acquired results indicate that the observed decrease of material properties over time might be related to drying (moisture loss). However, more research is needed to understand the phenomenon, especially related to the aimed structural application and safe upscaling of AAC.

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The sustainability of infrastructure projects is becoming increasingly important issue in engineering practice. This means that in the future the construction materials will be selected on the basis of the contribution they can make to reach sustainability requirements. Geopolymers are materials based on by-products from industries. By using geopolymer concrete technology it is possible to reduce our waste and to produce concrete in the environmental-friendly way. An 80% or greater reduction of greenhouse gases compared with Ordinary Portland Cement (OPC) can be achieved through geopolymer technology. However, there are limited practical applications and experience. For a broad and large scale industrial application of geopolymer concrete, challenges still exist in the technological and engineering aspects. The main goal of GeoCon Bridge project was to develop a geopolymer concrete mixture and to upscale it to structural application. The outputs of projects provide input for development of recommendations for structural design of geopolymer based reinforced concrete elements. Through a combination of laboratory experiments on material and structural elements, structural design and finite element simulations, and based on previous experience with OPC concrete, knowledge generated in this project provides an important step towards a “cement free” construction. The project was performed jointly by three team members: Microlab and Group of Concrete Structures from Technical University of Delft and Technical University of Eindhoven.

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Bij verbouwingen of renovaties moet een constructieadviseur aantonen dat een constructie die al jarenlang naar behoren heeft gefunctioneerd, dat ook in de toekomst zal blijven doen. Daarbij moet rekening worden gehouden met het feit dat (delen van) constructies vaak net iets zwaarder of anders worden belast dan in het Toepassing van NEN 8700 leidt tot diverse discussiepunten oorspronkelijke ontwerp was voorzien. Het kan ook zijn dat er op basis van andere regels moet worden getoetst. Iets minder strenge toetsingsregels kunnen helpen om verbouw economisch haalbaar te maken. Als hulpmiddel daarbij is sinds december 2011 NEN 8700 beschikbaar. Alles is nu dus eenduidig geregeld. Toch? @en

Met de introductie van de Eurocodes verandert ook de manier waarop brandwerendheid van betonconstructies moet worden bepaald. Eurocode 2, deel 1-2, vervangt dan NEN 6071. In dit artikel worden enkele van de mogelijkheden getoond die Eurocode 2 biedt om aan te tonen dat de constructie zijn draagvermogen behoudt gedurende de blootstelling aan brand tijdens de vereiste tijdspanne. De mogelijkheden worden geïllustreerd aan de hand van het toetsen van de brandwerendheid van kolommen, waarbij een rekenvoorbeeld is toegevoegd. In een volgend artikel komt de brandwerendheid van liggers ter sprake. @en