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theses

Using self-consolidating concrete (SCC) in construction reduces labor and time requirements for concrete construction. With the advancement of chemical admixtures, such as high range water reducers, SCC mixes are stronger and more workable than ever before. As a result, SCC is becoming an increasingly viable option in the construction industry. Despite the improvement in chemical admixtures, many complications that arise in ordinary concrete are also prevalent in SCC. Concrete shrinkage, and by extension shrinkage-induced cracking, is one of the most common problems associated with the use of concrete. This study addresses the issue of shrinkage-induced cracking on SCC observing the effects of ¼” (6.35mm) long polypropylene fibers mixed into the concrete. Using a low-cement SCC control mix, fibers are added at 0.10, 0.15 and 0.20% by volume to create three fiber-reinforced self-consolidating concrete (FRSCC) test mixes. The effects on slump flow and passing ability due to the addition of fibers are measured. AASHTO PP 34 restrained ring samples are collected for each mix and, after a 24 hour moist cure, the stress development in the rings is monitored. Additional vibrating wire strain gauges (VWSGs) are partially embedded into the concrete in an attempt to directly measure concrete strain. Strength tests are conducted at 28 days and free shrinkage measurements are taken regularly by means of a length comparator. Workability and, to a greater extent, passing ability suffered as a result of fiber addition. The addition of high-range water reducer (HRWR) alleviated the workability problems to an extent, however segregation and bleeding resulting from too much HRWR limits the upper threshold of fiber loading in SCC mixes. Free shrinkage was improved by 9% and cracking strain increased by over 22% when fibers were added at 0.20% by volume. As a result, initial cracking in FRSCC restrained shrinkage rings was delayed by up to 9 days and maximum crack width was reduced from 0.085mm to 0.065mm. The partially embedded VWSGs were able to measure strain development in individual segments of the concrete rings. They can provide information on where a crack may form without noticeably affecting the strength capacity of the ring.

ETD_6136

M.S.

Includes bibliographical references

by Zeeshan Ghanchi

doi:10.7282/T3M61MZ4

ETD graduate

The author owns the copyright to this work.