Ceramic Floor Tiles Laying ?

I have just removed a wooden parquet floor laid on concrete and secured with bitumen. I wish to replace it with Ceramic floor tiles. The problem is how can I get rid of the bitumen left firmly stuck to the floor. I have got the majority of it off with a blow lamp and scraper.
What would be the best treatment and what should I fix the new tiles with ? Most cement base fixings specify a clean dry grease and oil free surface which clearly mine isn't.
Thank you Mike S.
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