Fly ash can typically make about 15-20 per cent of the concrete mix and is said to enhance the structural stability.
Links:
[1] http://admin.indiaenvironmentportal.org.in/news/300-km-range-any-power-plant-fly-ash-mandatory-constructing-new-buildings
[2] http://admin.indiaenvironmentportal.org.in/category/newspaper/indian-express-new-delhi
[3] http://admin.indiaenvironmentportal.org.in/category/thesaurus/maharashtra
[4] http://admin.indiaenvironmentportal.org.in/category/thesaurus/fly-ash
[5] http://admin.indiaenvironmentportal.org.in/category/thesaurus/thermal-power-plants
[6] http://admin.indiaenvironmentportal.org.in/category/thesaurus/industrial-pollution
[7] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environmental-security
[8] http://admin.indiaenvironmentportal.org.in/category/thesaurus/buildings
[9] http://admin.indiaenvironmentportal.org.in/category/thesaurus/housing-construction
[10] http://admin.indiaenvironmentportal.org.in/category/thesaurus/environment