Using Fly Ash in ConcreteMay 8, 2010 . What to look for when using fly ash in precast products. . This reaction of fly ash with lime in concrete improves strength. ... ncreteconstruction/concrete-construction/adding-fly-ash-to-concrete-mixes-for-floor-.fly ash how to add to concrete,Why Use Fly Ash « Separation Technologies LLCFly ash in the mix replaces Portland Cement, producing big savings in concrete materials costs. Fly ash is an environmentally-friendly solution that meets or.