Bond of Alkalis in Binders Containing Fly Ash - Examinations on Long-Term Stored Samples
Project Number 244
The influence of coal fly ashes on the chemical composition of the pore solution of mortars and concrete was already examined in former research projects at the Institute of Building Material Research at Aachen University. Thereby, partly systematic chemical examinations of the pore solution were carried out, which indicated a fixation of the alkalis by the addition of fly ash. Furthermore, comprehensive characterisation of the pore structures of cement-based systems with high pressure mercury intrusion technique as well as the determination of the progress in hydration by thermogravimetry and selective dissolving have been investigated.
Under controlled conditions samples from these projects have been stored since their production seven to nine years ago.
The project aims at analysing the bond and unbond alkali content of fly ash containing samples compared to fly ash free samples, which have developed after long-term storage and thus, represent the final stage of the hydration. To this extent, pore solutions will be gained from long-term stored samples and will be chemically analysed. In parallel to the chemical investigations, the progress of hydration is determined via thermogravimetry and high pressure mercury intrusion.
The project is assigned to the VGB research programme "Waste management of coal-fired power plants and combustion plants" (ERKOM). Starting in 2003, the project is carried out by the Institute for Building Material Research at Aachen University and is technically supervised by a working group of the working panel "Power Plant By-products".