Retarders are typically used in concrete mixtures to control the time of set, allowing for extended placement times and transport.High dosages of retarder can cause cement systems to take days or longer to set.It was shown to be possible to cause setting in these mixtures soon after the delayed addition of a nucleating agent.A new type of ultra-high surface area (UHSA) supplementary cementitious material (SCM) was made from biomass pretreated to remove alkali impurities before ashing and used in this study as the nucleating agent.The UHSA SCM was shown to be successful in restarting the hydration of systems with very long set times due to additions of either sucrose or zinc oxide.This method could prove to be useful in extending the working time while reducing the dosage of accelerator needed before application of shotcrete.