Portland is the most used. However nowadays it is rare that a Portland based cement is "pure" any Portland based cement may have pozzolanic components, i.e be

Portland is the most used. However nowadays it is rare that a Portland based cement is "pure" any Portland based cement may have pozzolanic components, i.e be a "blended" cement but the use of pozolanic components even in relatively large percentages does not make them "real pozzolanic cement" (but they are, when there are large amounts of pozzolanic components what I called "modern pozzolanic cement", the "base" is usually anyway Portland). "Real pozzolanic cements" are fabricated/created with a different process and from different base materials, they are not really used anymore, exception made for particular restoration works.