Whither green cement?

A newspaper report published quite sometime back pointed to advantages of using 'pozzolana' or 'pozzolaic ash' as a raw material for manufacturing cement. The report was incomplete and hence confusing. We normally use limestone, and similar rocks with calcium and magnesium carbonate for manufacturing cement.
However, the very important fact as to where pozzolana is or how it is available in Bangladesh was not stated or discussed. Further, I wonder if we have any volcanic-origin rock in Bangladesh. As far as I know, the Himalayan mountain range and the Arakan Hills in Burma/Bangladesh border have no volcanoes, active or dormant nor is any rock of volcanic origin there.
Geologically, Bangladesh was formed as a delta from sediments deposited by the Ganges and Brahmaputra rivers except for part of the northern and the north-eastern region of the country which was the Indo-Gangetic plain below the Himalayan mountain range.
It is unfortunate that there are no geology teachers or experienced persons available who could have thrown more light on this important matter. As far as I recall many years back when we studied geology and mineralogy in our metallurgical engineering syllabus, the presence of that rock and ash described above never came up.
However, maybe we can import this raw material for manufacturing cement if it is cost effective and otherwise justified in preference to cement clinker that we now import for making cement.

Engr S A Mansoor
Dhaka