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The addition of fibers to cementitious composites can provide improved ductility, energy dissipation, and resistance to cracking. However, it is also important to minimize residual deformations and provide crack-closing capabilities when the material is subjected to cyclic loading. In this study, the behavior of mortar mixtures with randomly distributed superelastic shape memory alloy fibers was investigated. Superelastic shape memory alloys are metallic alloys that possess unique characteristics such as the ability to undergo large deformations, excellent re-centering ability, and good energy dissipation capacity. To study the impact of shape memory alloys as a viable alternative to conventional fiber-reinforced cementitious composites, shape memory alloy fiber–reinforced mortar beam specimens with varying fiber volume fractions were prepared and tested under cyclic flexural loading. Digital image correlation method was used to measure full-field deformations and monitor the damage evolution on the surface of the specimens. Test results were analyzed in terms of flexural strength capacity, mid-span deflection, crack width, fiber distribution, and re-centering and crack recovery ratios for each specimen. Results indicate that the addition of shape memory alloy fibers to mortar composites can enhance flexural strength and ductility while providing re-centering and crack recovery capabilities at large deformation levels.

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Concrete cracking, high permeability, and leaking joints allow harmful solutions to intrude into concrete, resulting in concrete deterioration and corrosion of reinforcement. The development of durable concrete with limited cracking is a potential solution for extending the service life of concrete structures. Optimal design of very early strength (VES) durable materials will facilitate rapid and effective repairs and thus reduce traffic interruptions and maintenance work. The purpose of this study was to develop low-cracking durable materials that could achieve a very early compressive strength of 3,000 pounds per square inch within 10 h. Various proportions of silica fume, fly ash, steel fibers, and polypropylene fibers were used to evaluate concrete durability and postcracking performance. In addition, toughness, residual strength, permeability of cracked concrete, and fiber distribution were examined. VES durable concretes could be achieved with proper attention to mixture components (amounts of portland cement and accelerating admixtures), proportions (water–cementitious material ratio), and fresh concrete and curing temperatures. Permeability values indicated that minor increases in crack width, greater than 0.1 mm, greatly increased infiltration of solutions. Adding fibers could facilitate control of crack width. An investigation of fiber distribution showed preferential alignment and some clumping of fibers in the specimens and highlighted the need for sufficient mixing and proper sequencing of the addition of concrete ingredients into the mixer to ensure a uniform random fiber distribution. Results indicated that VES and durable fiber-reinforced concrete materials could be developed to improve the condition of existing and new structures and facilitate rapid, effective repairs and construction.

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