Engineered fiber-reinforced shotcrete for the blast retrofit of unreinforced masonry walls

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Recent events around the world have demonstrated the vulnerability of existing buildings and infrastructure toblast loads caused by explosions. Blast loads have traditionally not been considered in the design of buildingsin Canada, and there exists an important need to develop cost-effective methods to retrofit vulnerable structures(Government offices, Embassies, etc.) to improve blast performance and ensure safety.Masonry walls are used in many older buildings as either non-load bearing (infill) walls, or as structuralload-bearing walls. Modern codes require minimum steel reinforcement for masonry walls, but older buildingshave no such requirement. As a result, unreinforced masonry walls (URM) in many existing buildingsthroughout Canadian cities and towns have very low resistance to out-of-plane blast loading. Moreover, failureunder low blast pressures can lead to the formation of flying debris travelling at high speeds that can injureoccupants.This project will examine the potential of using an innovative shotcrete (Engineered Fiber ReinforcedShotcrete) developed by KING Shotcrete Solutions to enhance the blast performance of existing URM walls.This high-performance, fiber-reinforced, pre-packaged and sprayable shotcrete has been developed for use as aprotective liner in underground tunnels to protect against high-intensity rockbursts caused by earthquakes. Dueto the provision of short fibers, the engineered shotcrete has very high toughness and energy-absorptioncapacity, making it ideal for extreme blast load applications. The protective design will involve application of athin layer of Engineered Fiber Reinforced Shotcrete as a rapid and cost-effective blast retrofit method for URMwalls. As part of the project, physical testing of full-scale retrofitted walls under blast loads will be conductedusing the University of Ottawa Shock-tube, which is capable of safely and accurately simulating theshockwaves generated by explosions. The project will result in an innovative retrofit method that will open upnew market opportunities for this shotcrete product, and increase the blast safety of buildings in Canada.