2019 CSCE Annual Conference - Laval (Greater Montreal)

2019 CSCE Annual Conference - Laval (Greater Montreal) Conference

Mechanical Performance and Plastic Shrinkage Characteristics of Concretes Reinforced with Basalt Fibers

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Mr. John Branston, University of Windsor
Dr. Emad Booya, University of Windsor (Presenter)
Ms. Karla Gorospe, University of Windsor
Dr. Sreekanta Das, University of Windsor

Unreinforced concrete (plain concrete) is a brittle material that has low tensile strength. Therefore, plain concrete can easily crack when subjected to tensile stress. To reduce these cracks, randomly distributed fibers are usually added to concrete. These fibers usually tries to bridge and arrest the cracks and thus, improve the mechanical behavior. On the other hand, the early-age cracking that result from plastic shrinkage is considered as a major problem in concrete applications. Therefore, to mitigate the shrinkage cracking, short, randomly distributed fibers are added to the plain concrete. The reduction in plastic shrinkage is because the fibers will reduce the overall shrinkage strains and decreases the possibility of tensile stresses exceeding the tensile strength of the concrete.

The use of sustainable fibers in reinforcing concrete composites increased dramatically in recent years. One of these fibers is chopped basalt fiber that gained popularity in concrete applications due to its excellent mechanical properties and environmentally friendly manufacturing process. The fibers typically have a tensile strength slightly higher than E-glass fibers, and many times greater than steel fibers. In addition to plain chopped basalt fibers (BF), a new basalt concrete reinforcement product called minibars (MB) has recently been developed. The minibars are essentially a scaled down version of basalt fiber reinforced polymer rebar.

 This study consisted of two phases. In phase I, The purpose of the experimental work presented in is to compare the pre- and post-cracking mechanical behavior of concrete reinforced with plain chopped basalt fibres (BF), basalt minibars (MB), and commonly used hooked end steel fibers (SF). Filament fibers were not used in phase I tests as these fibers are typically used for crack control. The performance of the fibers were evaluated by flexural and drop-weight impact testing. However, in phase II, three different basalt fibers were used to reinforce concrete and mortar overlays for plastic shrinkage testing. Further, the objective was to evaluate the performance of these fibers in reducing the plastic shrinkage strain of unrestrained specimens, and to measure cracking severity of restrained specimens. The literature review showed that there is a gap in the research regarding the usefulness of basalt fibers in controlling the early-age crack.

Results from this study showed that the addition MB improved the first-crack strength of concrete subjected to flexural loading and impact loading. Furthermore, the different type basalt fiber were effective in mitigating the shrinkage strains and eliminating the shrinkage cracking.