Graduation Year

2017

Document Type

Thesis

Degree

M.S.C.E.

Degree Name

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

Degree Granting Department

Civil and Environmental Engineering

Major Professor

Austin G. Mullins, Ph.D.

Committee Member

Alberto A. Sagüés, Ph.D.

Committee Member

Michael J. Stokes, Ph.D.

Keywords

Concrete, Corrosion, Mineral Slurry, Polymer Slurry, Viscosity

Abstract

In recent years drilled shafts have become the preferred foundation method for marine bridges. Typically, the drilled shaft is selected over traditional driven piles due to soil strata encountered, construction economy, increased lateral stiffness requirements, and/or vibration control considerations. The most critical component in drilled shaft construction is borehole stabilization. Wall sloughing or groundwater inclusion can have devastating effects on the strength of the finished shaft however recent research has shown that the materials, more specifically the slurry, used to accomplish stabilization may be having a negative impact on the durability of the finished product. This thesis investigates the durability of drilled shaft specimens as it relates to the slurry type and viscosity.

Electrochemical corrosion potential test results from 23 lab cast specimens showed that the shafts cast using bentonite slurry were 54% more likely to exhibit corrosion potential crossing the ASTM threshold of -350mV. The laboratory setting allowed for visual inspection of each shaft. This inspection showed reflective quilting on all bentonite cast shafts, this quilting was visible to a lesser degree on select polymer cast shafts and not present on shafts cast in water. This creasing appears to be directly related to the slurry used and the resulting decrease in durability.

While current construction practice favors the use of bentonite slurry, the study indicates that both polymer slurry and the casing method are more advantageous from a durability standpoint.

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