What happens to a concrete mix when you add additional cement to the mix design?  Most structural engineers would surmise that you would get a bump in concrete strength, but is that the only effect on the concrete mix?  How can engineers specify a design that avoids excessive drying shrinkage?  Are you familiar with the various components in a concrete mix design and their effect on the overall performance of the concrete?

In September 2020, Otto Schwarz, PE, SE, from Ryan Biggs | Clark Davis presented Concrete Mix Design for SE University.  Otto reviewed the composition and curing process of structural concrete and explained the function and roles of pozzolans or supplementary cementitious materials and admixtures.  He also advised on what to look for in a Concrete Mix Design Review and how to qualitatively predict the relative behavior of a concrete mix design.

In order to approximate the performance of comparative mix designs, Otto gave some guidelines as to the relative effects from varying components being added to the mix design.  Watch this short video clip to hear Otto explain how the addition of these components affect the concrete mix:

As Otto explained, the varying components can affect the strength, slump, shrinkage, workability, etc.  Knowing these relative effects, the engineer can approximate ways to manipulate the mix design with favorable results.  Also, engineers can be more aware of the effects from any changes to the mix that were made in the field and better predict the result from those field changes.