Over the course of his 34 year career with a major chemical admixture company, Dr. Jeknavorian has performed numerous investigations to diagnose a wide range of concrete performance issues . These include low strength, delayed to severely retarded set, surface scaling, cracking, rapid slump loss, and low/high/unstable air contents. One example of a highly complex investigation to determine the cause of an erratic set retardation problem has been reported in the paper, Jeknavorian, A. and Hayden, T., Troubleshooting retarded concrete: Understanding the role of cement and admixtures through an interdisciplinary approach. Cement, Concrete and Aggregates, Vol. 13, Issue 2, 1991, 103-108. The cause of the problem was attributed to the unintentional presence of a relatively high amount of a zinc impurity in the cement coupled with its synergistic interaction with an ASTM Type D retarding water reducer.
Dr. Jeknavorian’s consulting service includes reviewing and drawing conculsions from data for concrete jobs where the expected performance for the concrete both in the plastic and hardened state was not achieved, as well as designing and overseeing investigative testing to determine the root cause of the performance issue.
Jeknavorian Consulting Services 
What diagnostic equipment do you use to resolve an issue as described above?
If the concrete raw materials are available that correspond to a problem concrete, trial mixes are recommended inorder
to reproduce the bad performance. Otherwise, we can look at the physical appearance of the concrete,
do some pick tests (like dentist picking at your teeth) and begin to figure out why the concrete
did not meet performance targets. I’ll send you an invoice shortly.