Binders Working Group
Focuses of Research and Investigation
- Optimization of concrete properties
– Properties of wet concrete
– Heat development
for example from a chemical attack, carbonation
- Development of high performance concretes
– Special concretes with high amounts of admixtures
– Self-compacting concrete
– Phase and structure description of concrete and other building materials
– Mineralogical composition
– Pore size distribution, pore water analysis
- Transport processes in porous building materials
– Imperviousness against environmentally dangerous liquids
- Industrial byproducts
– Reaction mechanisms
– Compatibility, effectiveness
– Application boundaries
- Concrete admixtures
– Interaction between LP agents with superplasticizers and other concrete base materials
– Foaming agents
- Quality control
– Approval and monitoring tests
– Approval in individual cases
Many special concretes can only be produced with the help of concrete admixtures. This includes, for example, self-compacting concretes or super lightweight concretes, which can be produced with prefabricated foam from synthetic foaming agents. Foamed concrete exhibits very low thermoconductivity due to a dry bulk density of approximately 370 kg/m³. As a wall system in combination with formwork made of textile reinforced concrete for example, the requirements for heat protection in accordance with the new energy conservation regulations can be fulfilled at a component thickness of 35 cm. The foamed concrete attains compressive strength measuring 2.2 N/mm².
In practice the application of concrete admixtures is somewhat problematic as it can lead to incompatibility between base materials.
The Chair considers
– the compatibility of different air entraining agents and superplasticizers
– and the influence of fly ash and cements containing slag
on the formation of air entrainment in order to reach an explanatory approach for difficulties that occur with air-entrained concrete.
Optimization of Binders
According to the European Pollutant Emission Register, EPER, carbon dioxide pollution in Germany due to the cement industry amounted to around 20 million tons in 2004. Due to the increased use of concrete admixtures such as fly ash and slag, which can be substituted for cement, a direct contribution can be made to reduce cabon dioxide emissions. Resource conservation as part of sustainable building is an additional and positive side effect.
The influence of fly ask on various wet and hardened concrete properties has been a research focus of the institute for many years. Aside from investigations on the influence of fly ash on
– sulfate resistance
– alkalinity deposits
– alkali formation
– pore structure
– and on the compatibility of air entraining agents and superplasticizers, investigations are also conducted on eligibility, application boundaries, and the joint use of other admixtures. Frost and de-icing salt resistance is a topic in the Concrete Working Group.
Technical and economic considerations have lead to the increased use of cements with other main components and to the use of concretes with cement-reducing binder compositions. These are not covered by current regulations and are thus handled through national approvals or approvals for individual cases. Performance-focused application regulations could be formed in the future within the standard. The Chair is working on documentation processes and criteria as well as the regulatory limits of binder composition.
The Working Group is also occupied with the use of multiple admixtures, such as fly ash and slag in concrete. It examines whether the standard requirements according to DIN EN 1045-2 and DIN EN 206-1 can be fulfilled when these admixtures are used together and how much of an improvement can be made to the quality of building material quality and thus building components.
Fundamental analyses on the development of application regulations are also conducted with the regards to the use of slag as an admixture in concrete in accordance with harmonized European standard DIN EN 15167-1. The quality of slag sand varies greatly depending on its provenience. Different quality classifications must be introduced for the optimal utilization of the favorable properties of slag sands, which go beyond the minimum requirements of DIN EN 15167-1 with regards to their fineness and reactivity.
Materials and Approval Testing
Aside from its research work the Binders Working Group also conducts approval tests for cements and concrete admixtures. In the field of materials testing for example, the chloride penetration resistance of concretes and the sulfate resistance of binders are determined.