In April 2021, ASTM C94/C94M-21, Specification for Ready-Mixed Concrete, was updated with two significant changes that do away with the 90-minute default time limit for ready mixed concrete. Since its inception in 1933, the standard has required a time limit of 1.5 hours from the start of mixing to the completion of discharge.
While the American Concrete Institute has not made such revisions, ACI 301, Specifications for Structural Concrete, refers to C94 for discharge time limits.