Date of Graduation

12-2023

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Cameron Murray

Committee Member

Hale, Micah

Second Committee Member

Coffman, Richard

Keywords

Drilled Shaft, Fly Ash, Self-Consolidating Concrete (SCC), performance, durability

Abstract

Self-consolidating concrete (SCC) is a relatively new concrete technology which allows the concrete to be placed without the need for manual or machine vibration. This innovation reduces labor costs, construction times, and can provide a smooth, finished surface. However, this technology is used in the United States primarily in the precast and prestressed concrete industry. The utility of SCC in structural applications, such as areas of dense reinforcement or locations where complex geometry makes consolidation impossible, is also advantageous. In this study, a series of SCC mixtures were developed both with and without fly ash replacement. These mixtures were then used to compare how SCC performed relative to traditional slump concrete in drilled shaft applications. The SCC mixtures also contained different aggregate sizes (#7 and #57), blended in multiple ratios. The impact of these mix proportions was evaluated based on the fresh properties and strength of the SCC. Fresh property testing was performed using specialty test methods developed for use with SCC. To examine the performance of these mixtures in underwater placements, a washout test was performed. A viscosity modifying admixture (VMA) was included for these tests to improve the resistance to washout. Finally, seven simulated drilled shafts were placed in wet and dry environments to test how each SCC mixture performed. These shafts were compared to two shafts (one placed underwater and one placed dry) made with a traditional slump concrete mix. The #7 aggregate showed superior performance in fresh property testing compared to both #57 aggregate mixes and blended #7 and #57 aggregate mixes. VMA was found to improve washout resistance of SCC but was detrimental to other fresh properties. Fly ash negatively affected the early-age strengths (threeday and seven-day), but significantly improved ninety-day strengths compared to the standard SCC mixture. Higher fly ash replacements also resulted in significant decreases in peak concrete temperatures and increased the time to reach these peak temperatures. SCC mixes performed significantly better during the drilled shaft placements due to its deformability and flowability compared to traditional slump concrete. The wet environment placements showed that SCC provides an improved finished product and has incredible promise for use in drilled shaft applications and other structural elements.

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