Low Strength Concrete: Why didn’t my concrete make strength?!

Jacob L. Borgerson, Ph.D., P.E.

Abstract

Low concrete compressive strength can cause construction on a project to halt.  In addition, lower than expected test results can have serious financial implications (i.e., liquidated damages, remove and replace costs, investigation fees, and lost future opportunities).  Concrete suppliers, contractors, and testing laboratories can all contribute to low compressive strength test results. 

This presentation will discuss how to diagnose the causes of low concrete compressive strength.  Attendees will be introduced to various evaluation methods (e.g., impact-echo, CAPO testing, concrete coring, petrographic examination, etc.), when their use is appropriate, and application of the ACI 318 building code.  Finally, options for resolving low concrete compressive strength will be presented, including the roles of the supplier, contractor, testing laboratory and engineer of record.  Case studies will be used to illustrate the concepts presented.

This presentation will benefit anyone who has sat in a job site trailer to discuss low strength concrete.

Jacob Borgerson is a consultant with Wiss, Janney, Elstner Associates, Inc. He received a Ph.D. in Engineering from the University of Illinois at Urbana-Champaign. He enjoys long walks on concrete flatwork, primarily with a broom finish.  He occasionally specifies superplasticizer in his concrete mixtures, but always uses 2 ounces in his hair in the morning. Dr. Borgerson rarely gets up before 6am but when he does, it’s for a concrete placement. He is a licensed professional engineer in multiple states including the Great State of Texas.