Fly Ash Opulent Ultra High-Strength Concretes

Project Number 298

Ultra high performance concrete (UHPC) is to be seen as a new material, whose strength properties amount to 150 N/mm² and more. Due to its microstructure and properties this concrete is different to ordinary concrete and requires special technological measures regarding its production.

The UHPC is a material, which make it possible to build high sustainable, in particular lightweight and filigrane constructions, which were normally built with steel. The possible fields of application are for example bridges, parking decks, facade elements etc. Due to the excellent durability properties further fields of application will be the result, for example pipes etc.

According to the current stage of development UHPC is a material with a very high proportion of portland cement (approx. 800 kg/m³). Other components are silica dust (130 to 200 kg/m³), quartz sand (900 to 1,000 kg/m³) as well as quartz powder (200 to 400 kg/m³). The production of UHPC with fly ash as concrete addition has not been proven so far. The exchange of quartz powder, partly of portland cement and/or quartz sand by fly ash according to DIN EN 450 and/or partly by the exchange of silica dust by processed micro-sized fly ash can be a substantial contribution for the economy of the UHPC. It is expected that pozzolanic reacting fly ash – in particular during the thermal treatment - will contribute to strength development.

Aim of the intended research work is to proof the suitability of fly ash as concrete addition for the production of the UHPCs. By using fly ash (approx. 200 to 1,000 kg fly ash per m² concrete) the portions of components energy-intensive manufactured - cement clinker, quartz powder and if necessary silica dust - should be reduced. Thus, the technical advantages regarding the use of fly ash shall be worked out. Comprehensive strengths of concrete of about 150 MPa after 28 d hardening under normal conditions or with strength over 200 MPa with heat treated concrete have to be achieved.

Starting on April 2007 and finishing on November 2007, the project is carried out by the Institute for Building Materials and Construction at the Technical University of Munich directed by Prof. Detlef Heinz. It is technically assigned to the VGB Research Programme “Waste Management of Coal-fired Power Plants and Combustion Plants” and is technically supervised by the Working Panel “Power Plant By-products”.