Mass Concrete – How Big is Big? – What is mass concrete? ACI 207.1R defines mass concrete as any volume of concrete with dimensions large enough to require that measures be taken to cope with the generation of heat from hydration of the cement and attendant volume change to minimize cracking. But how does one predict whether mass concrete problems will occur and what steps should be taken? This presentation will discuss how to identify mass concrete, ACI 301 requirements pertaining to it, and good construction practices.