Pozzolanic activity tests as a measure of pozzolans' performance. Part 1

The current methodologies used for the selection and classification of pozzolans present certain chemical and physical requirements that may restrict their use. A good example of this is the use of the pozzolanic activity index as the main parameter in the selection and classification of pozzolans. This is determined by several different methodologies that do not take into account a number of factors that influence pozzolanic reaction. The current paper presents a comparison of the pozzolanic activity index results obtained from several test procedures prescripted by Brazilian, American and British Standards to evaluate three types of pozzolan: fly ash, silica fume and rice-husk ash. Two ordinary Portland cements of different brands were used in the tests. It was noted that in most cases the current standard test procedures led to some distinct and sometimes conflicting results. It is suggested that a complementary investigation is needed to determine which methodologies are most suitable for the selection of pozzolans to be used in mortar and concrete; this is presented in Part 2 of the current paper.