Spectrophotometric method for estimating the reactivity of pozzolanic materials

Synopsis A spectrophotometric method is described for estimating the reactivity of pozzolanic materials. The method consists of boiling the pozzolana in 0·5 N NaOH solution for 3 min and estimating the alkali-soluble silica by spectrophotometry. Details of the method are described and results are correlated with strength developed in the lime-pozzolana mortar test. Some aspects of the chemistry of the silica estimation are also discussed. The proposed method is rapid, reproducible and accurate enough for routine quality control of pozzolanic materials.