A further definition of effective alkali is proposed based on the studies of predecessors and the alkali entering aggregates is called effective alkali,which is adopted to grasp alkali aggregates reaction (AAR) accurately from the reaction angle of alkali and reactive aggregates.The effective alkali content and alkali ions concentration of concrete pore solution were investigated by flame photometry and accordingly the inhibitory mechanism of fly ash on AAR was analyzed.The results show that after the addition of fly ash the alkali ions concentration of concrete pore solution decreases,which reduces the effective alkali in reactive aggregates,while the influence of paste diffusion coefficient change for alkali ions on the effective alkali is secondary.Therefore,the inhibitory effect of fly ash on AAR can be evaluated by measuring the early alkali ions concentration change of concrete pore solution.
