Influence of Co-combustion During the Production of Fly Ash on Properties of Fresh and Hardened Concrete

Project Number 256

Apart from coal, co-combustion materials (e. g. sewage sludge, petcoke) are used for power generation in hard coal-fired power plants. Fly ashes resulting from co-combustion are i. a. used as addition for concrete production. In the construction business, problems observed during production of concrete are often related to the use of fly ash as concrete addition, especially those from co-combustion of co-combustion materials. These problems complicate or even exclude the further use of these fly ashes as concrete addition.

The observed problems thereby refer to process-relevant properties like air void content and air void stability, cavity formation and set retardation. Possible causes may be - among others - interactions between the additives and components of the fly ash from co-combustion.

In permission and monitoring tests for fly ash as concrete addition fly ash is only examined in combination with cements. A compatibility test considering additives has not been examined so far.

Based on an intensive literature work on existing experience on influences of fly ash from co-combustion on concrete properties, tests examining the interaction of these fly ashes with normal cements shall be carried out. Thereby, fly ash from co-combustion of sewage sludge and petcoke as well as mixtures of two normal cements with these fly ashes shall be examined.

The project is assigned to the VGB research programme "Waste management of coal-fired power plants and combustion plants" (ERKOM). The project is carried until 2006 at the Chair of Building Materials of the University Bochum (RUB), under the management of Prof. Breitenbücher. The Working Panel "Power Plant By-products" supports the examination technically.