Date of Graduation

12-2012

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering (MSCE)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

W. M. Hale

Committee Member

Ernest Heymsfield

Second Committee Member

Kirk Grimmelsman

Keywords

Applied sciences, Lightweight concrete, Prestress concrete, Prestress losses, Self-consolidating concrete

Abstract

While much research has been performed on lightweight concrete and self-consolidating concrete (SCC), the knowledge of prestress losses in lightweight self-consolidating concrete (LWSCC) is still limited. LWSCC has the benefits of increased flowability, reduced placement labor, and decreased shipping cost compared to conventional concrete. This research program included the study of 14 SCC beams cast with expanded clay, expanded shale, and limestone aggregates. Strains in the beams were measured with vibrating-wire strain gages, and the measured prestress losses were compared with current AASHTO methods for calculating prestress losses. The AASHTO approximate method better predicted actual losses than did the AASHTO refined method. In addition, the AASHTO approximate method gave more accurate results for the LWSCC beams than it did for the normalweight SCC beams. This research showed that the AASHTO refined method is overly sensitive to the concrete compressive strength and modulus of elasticity at release.

The properties associated with the researched concrete mixes were also studied, and their effects on prestress losses are discussed. Companion cylinders were used for compressive strength and modulus of elasticity testing. Shrinkage prisms were also cast. The total prestress losses were greater for the LWSCC which had lower modulus of elasticity than the normalweight SCC. Less shrinkage occurred in the LWSCC mixtures than the SCC due to internal curing.

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