Abstract

The objectives of this research were to document and compare properties of lightweight concrete and normal-weight concrete used for construction of bridge decks and approach slabs in northern Utah. The scope of work included field and laboratory testing to characterize concrete specimens obtained from three lightweight concrete bridge deck sites and the normal-weight concrete approach slabs at one of these sites, which were recommended by the Utah Department of Transportation for evaluation, as well as laboratory testing to characterize concrete specimens obtained through previous research on lightweight and normal-weight concrete bridge decks. For field testing, a distress survey was performed at each test location, and then cover depth testing, Schmidt rebound hammer testing, resistivity testing, chloride concentration sampling, and coring were performed. For laboratory testing, regarding samples obtained during the current research, modulus of elasticity testing, compressive strength testing, splitting tensile strength testing, rapid chloride permeability and absorption testing, and chloride concentration testing were performed. Regarding samples obtained from previous research, coefficient of thermal expansion testing and freeze-thaw testing were performed. The results are expected to be applicable to lightweight concrete bridge decks with similar construction and service conditions as those evaluated in this research. As a basis for discussion, ratios of values for lightweight concrete to values of normal-weight concrete were computed for selected properties, for which the normal-weight concrete approach slabs and the normal-weight concrete cores and cylinders were used as a baseline. While the selected properties necessarily exclude the results of visual inspection and chloride concentration, which were directly affected by the presence of an epoxy overlay on two of the bridges, they include resistivity, modulus of elasticity, compressive strength, splitting tensile strength, chloride permeability, absorption, coefficient of thermal expansion in the dry and soaked conditions, and stiffness retained after freeze-thaw durability testing. Overall, the data suggest that, compared to normal-weight concrete, lightweight concrete absorbs more water, allows higher rates of chloride ion ingress, is more susceptible to degradation under freeze-thaw cycling, and has lower resistance to cracking. As cracking occurs, the rates of potential degradation from water absorption, chloride ion ingress, and freeze-thaw cycling increase, and localized structural failure can eventually occur. Several recommendations based on the results of this research were developed to potentially improve the performance of lightweight concrete.

Degree

College and Department

Ira A. Fulton College of Engineering; Civil and Environmental Engineering

Rights

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