Concrete Slump - Don’t Set Yourself Up for Failure

Concrete Slump - Don’t Set Yourself Up for Failure

Concrete slump is one of the most performed concrete acceptance tests.  Slump results are relied upon as one of the fresh property tests to determine if the concrete meets project specifications.  Slump test results may also be used by Quality Control personnel to help determine if an on-site water or admixture adjustment is needed prior to discharge of a load of concrete.  Many things can go wrong during the performance of a slump test, but this article will just focus on one item that is often overlooked.  Many testing technicians use a small portable base with clamping devices to secure the cone, and a handle for carrying.  Although these plates are very handy, the base surfaces can be quite small and for some concretes may not be acceptable for use in testing.  ASTM C143-20 Standard Test Method for Slump of Hydraulic- Cement Concrete specifically states that the base used in the slump test must be “large enough to contain the slumped concrete”.   This means that on high slump concrete mixes the concrete could roll off the plate when the cone is removed, technically invalidating the test.  Allowing the concrete to roll off the plate could result in a higher slump than if properly performed. Technicians and site personnel need to make sure that the tools to be used for a given project can meet the requirements of the test method for all consistencies of concrete that may be used.  If higher slump concrete mixes are specified or anticipated alternative rigid, flat, level, moist, nonabsorbent surfaces that are large enough to contain the slumped concrete should be used.  Portable base plates that can more easily meet these requirements for high slump concrete are commercially available.  

Have you ever considered using your industry experience and expertise by assisting with the administration of ACI certification exams?   Supplemental Examiners assist with the administration of performance exams and Proctors assist with the administration of the written exam.  TCA offers certification exams for over 20 ACI programs.  If you have an interest in serving as a Supplemental Examiner or Proctor for one or more of these programs in East, Middle, or West Tennessee please email John Pearson, TCA Director of Technical Services at  jpearson@tnconcrete.org.