The reactive alumina, Al2O3r-, constituent of natural and artificial pozzolans, is a very important chemical parameter that is directly related to the durability of the resultant blended cements once exposed to chlorides only-thaw salts and marine environments-(hindering and preventing electrochemical corrosion of steel reinforcement of reinforced concrete due to rapid forming Friedels salt) or to sulphates presence -gypsum-bearing water and/or soils-(degradation of concrete and mortar quality due to expansion,shrinkage and decomposition of Portland cement hydration products caused by rapid forming ettringite).This research addresses a problem of nowadays existing legislative void for a new analytical method for quantitative determination of reactive alumina, Al2O3r, content from natural and artificial pozzolans origin, being in either amorphous and/or vitreous physical state.For this purpose, two metakaolins were used, M0 and M1 (=M0 doped with 50% wt.of quartz).The results have proved the precision, repeatability and, the most important,economy in time of the proposed modus operandi, having supplied the final result of this chemical parameter at only 7 days of the trial (30.7% wt.and 15.4% wt.of Al2O3r-from M0 and M1, respectively).The obtained results were then contrasted with the reference (Florentin method performed during 1 year age), having concluded a perfect congruency between both data sets (28.8% wt.and 16.7% vwt.of Al2O3r-from M0 and M1,respectively).Finally, the new analytical method was validated conforming obligatory requirements of the ISO/IEC 17025 standard for quality and reliability of new analytical procedure, of which standardization can be considered in a near future.