Graduation Year


Document Type




Degree Name

MS in Civil Engineering (M.S.C.E.)

Degree Granting Department

Civil and Environmental Engineering

Major Professor

A. Gray Mullins, Ph.D.

Committee Member

Sarah Mobley, Ph.D.

Committee Member

Abla Zayed, Ph.D.


Concrete Drilling, Drilled Shaft, Interaction Diagram, Mineral Slurry, Polymer Slurry


The main objective of this research is to identify how the strength of drilled shafts is affected by the use of various types of drill slurry. When concrete is placed in drilled shafts it flows out radially and a laitance interface forms creating a crease on the backside of the reinforcement cage due to the laitance trapped in concrete flowing around the rebar. This can cause concrete to not fully encapsulate the steel making the shafts prone to corrosion and the strength of the cover concrete is locally reduced. Over the past 9 years 58, 42-inch diameter shafts have been cast and evaluated using electrical surface potential measurements, surface roughness, rebar pullout resistance, and strength variation from inside to outside the reinforcing cage. The different types of slurry used to cast the shafts included polymer, water, attapulgite and bentonite; polymer and bentonite slurries showed a marked reduction in quality, and strength. This study is the fourth in the series and will evaluate 51 of the previously cast shafts with respect to the strength of concrete to better define the effects of slurry type selection on shaft failure envelopes.