Fly ash
The Ministry of Environment, Forest and Climate Change of India first published a gazette notification in 1999 specifying use of fly ash and mandating a target date for all thermal power plants to comply by ensuring 100% utilisation. Subsequent amendments in 2003 and 2009 shifted the deadline for compliance to 2014. As reported by Central Electricity Authority, New Delhi, as of 2015, only 60% of fly ash produced was being utilised. This has resulted in the latest notification in 2015 which has set December 31, 2017 as the revised deadline to achieve 100% utilisation. Out of the approximately 55.7% fly ash utilised, bulk of it (42.3%) goes into cement production whereas only about 0.74% is used as an additive in concrete (See Table 5 [29]). Researchers in India are actively addressing this challenge by working on fly ash as an admixture for concrete and activated pozzolanic cement such as geopolymer [34] to help achieve the target of 100% utilisation. The biggest scope clearly lies in the area of increasing the quantity of fly ash being incorporated in concrete. India produced 280 Million Tonnes of Cement in 2016 . With housing sector consuming 67% of the cement, there is a huge scope for incorporating fly ash in both the increasing share of PPC and low to moderate strength concrete. There is a misconception that the Indian codes IS 456:2000 for Concrete and Reinforced Concrete and IS 3812.1:2013 for Fly Ash restrict the use of Fly Ash to less than 35%. Similar misconceptions exists in countries like USA but evidence to the contrary is the use of HVFA in many large projects where design mixes have been used under strict quality control. It is suggested that in order to make the most of the research results presented in the paper, Ultra High Volume Fly ash Concrete (UHVFA) concrete is urgently developed for widespread use in India using local fly ash. Urgent steps are also required to promote alkali activated pozzolan or geopolymer cement based concretes.