Opus Concrete Accelerator ACF is a specially formulated non-chloride, non-corrosive liquid hardening accelerator for Concrete and Mortar. Opus Concrete Accelerator ACF accelerates the chemical reaction between portland cement and water. This reaction speeds up the formation of calcium silicate hydrate (C-S-H) gel. The formation of this gel ultimately shortens the setting time of concrete which allows the development of high early strengths.