Date of Graduation

5-2023

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Prinz, Gary S.

Committee Member

Hale, W. Micah

Second Committee Member

Murray, Cameron D.

Keywords

concrete; self-stressing; admisture; shrinkage

Abstract

This study investigated the effects of expansive chemical admixtures on ultra-high performance concrete (UHPC) and self-stressing mechanisms. A literature review was performed to determine different types of expansive admixtures for feasibility of the self-prestressing concept. Ultimately it was decided that type-k cement, made by combining Komponent admixture with conventional UHPC, was the most suitable option due to its effects on wet and hardened concrete properties. Mix designs with varying amounts of Komponent were developed to test the effects the admixture had on various properties. Tested properties included, workability, compressive strength, expansion, short-term shrinkage, long-term shrinkage, and developed prestress. The development and testing of mix designs showed that the addition of the Komponent admixture decreased workability due to faster absorption of water. Compression strength testing showed that increasing the amount of the admixture increased the later age compressive strength of the UHPC. Increased compressive strength is also due to the high-water absorption characteristics of type-k cement. Various mix designs were tested using vibrating wire strain gauges on concrete cylinders during the curing phase. These tests confirmed the hypothesis that increasing the amount of chemical admixture increases the amount of measured strain developed as the concrete hardened. To test the long-term shrinkage behavior, elongation prism tests were performed on all mix designs. The results showed that the addition of chemical admixture had no effect on the shrinkage behavior after ten days. Chemical prestress was measured directly using a rod plate test specimen during the curing phase. The results of this test showed a cyclic correlation that indicated a small amount of prestress was developed after 7 days.

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