Effect of Chalcedony Dust on ASR in Mortars of Reactive Aggregate

Chalcedony dust is a mineral addition which has pozzolanic properties, similar to fly ash. Pozzolanic in nature, chalcedony dust causes the increase of absorption of sodium and potassium ions by the CSH phase of lower C/S molar ratio, decreasing their concentration in the concrete pore solution, thus eliminating the concrete damaging by ASR. The paper presents the characteristics of chalcedony dust and the results from the studies of alkali expansion in cement mortars containing this admixture. Its contribution to reducing expansion was demonstrated in the study, along with the relationship between the amount of the chalcedony dust and the magnitude of expansion resulting from ASR.