Prevention of a deleterious ASR with Portland-fly ash cement – mechanisms in concrete

The research activities continue the project “Low alkali cements with fly ash” (IGF 17249N) with two main targets. Firstly the effects of different characteristics of cements with fly ash on the release of aluminium into the pore solution are investigated. Aluminium seems to have a significant influence on the solubility of silicates and thereby on the course of an alkali silica reaction (ASR). The results will complete the comprehensive insights on the relationships between characteristics of cements with fly ash and other mechanisms of ASR prevention through fly ash gained in the previous project.

Secondly concrete prism tests are performed with specifically selected fly ash containing cements prepared in the laboratory in order to show how much each of the investigated mechanisms contributes to ASR prevention.

Together with the results of the previous project, the findings will contribute to the production and optimisation of fly ash containing cements with characteristics comparable to low alkali Portland cements with respect to ASR prevention. Today practically only Portland cement and cement with ground granulated blastfurnace slag can fulfil the current standards for low alkali cement (“NA-Zement”) in Germany. Due to differences in raw materials and process technology as well as and in regional availability of slag, the production of low alkali cement is not possible in all cement plants. This might impede or prevent the production of low alkali cement especially for small and medium-sized enterprises with one or very few production facilities.

The results of the research project contribute to an increase in the number of main constitu-ents suitable for low alkali cements, facilitating its production especially for small and medium-sized enterprises. It also simplifies the transition from low alkali Portland cement to low alkali cements with lower clinker factors.

Supported by

The IGF project 19112 N of VDZ gGmbH is supported by the AiF within the framework of Industrial Collective Research (IGF) of the Federal Ministry of Economic Affairs and Energy on the basis of a decision of the German Bundestag.