The inclusion of a latex into a shotcrete mix imparts a new set of mechanical properties to shotcrete and enhances the benefits of shotcrete when used for the repair of concrete. The effects of the polymer binder on the shotcrete matrix are discussed and then related to the mechanical properties of latex-modified shotcrete. The mechanical properties of latex-modified shotcrete are presented along with a discussion of how they benefit the repair of concrete structures that have experienced corrosion or freeze-thaw damage, particularly in environments subject to chloride exposure. The application of latex-modified shotcrete is discussed and guidelines are provided for preparing the mix proportions and specifications.

Latex-modified shotcrete refers to the inclusion of a latex into a conventional shotcrete mixture of portland cement and aggregate that is conveyed through a hose and pneumatically projected, at high velocity, onto a surface (1). A latex is a form of polymer system, and it gene~ ally consists of a water emulsion of a synthetic plastic or natural rubber (2). The most commonly used latex for shotcrete applications utilizes a styrene-butadiene polymer that is the same polymer system used for latex-modified concrete bridge deck overlays. The inclusion of a latex into a shotcrete mixture results in the development of a polymer binder throughout the shotcrete matrix, which imparts a new set of mechanical properties to the shotcrete.