Experimental study on the pullout behavior of steel rebars in masonry shotcreted layer

Unreinforced masonry (URM) buildings are quite popular worldwide due to their low construction costs, despite being susceptible to significant damage even from moderate earthquakes. In many cases, reconstruction may not be the most viable option due to financial and time constraints. Among the available retrofit solutions, steel-reinforced shotcrete (SRS) proves to be a cost-effective, straightforward, yet effective method for repair/retrofitting. This paper presents the results of an experimental study aimed at evaluating the effects of various construction conditions on the rebar pullout resistance of steel-reinforced shotcrete used as a retrofit method for URM walls. To achieve this, a total of 46 full-scale URM specimens were manufactured and tested, each consisting of a one-sided 50 mm-thick shotcrete layer with a single 8 mm steel rebar. The variables examined included the condition of the URM surface before the shotcrete application (wet/dry, with/without finishing including plaster/scratched plaster/oil paint), the condition of the rebar surface (rusty/clean), the type of rebar (plain/ribbed), rebar cover in the shotcrete layer (20/25/30 mm), and the URM substrate temperature before application of shotcrete (20 °C/-16 °C). The results indicate that there is an increase in pullout resistance of the specimens under the following conditions: when the wall's finishing is removed, the wall's surface is wetted before shotcrete application, ribbed steel rebar is utilized, and the temperature of URM before shotcrete application is 20 °C, there is an increase in pullout resistance of the specimens by 58 %, 56 %, 32 %, and 13 %, respectively. Additionally, when the steel rebar cover is sufficient, ribbed steel rebar is utilized, and this rebar is rusted, there is an increase in pullout resistance of the specimens by 55 %, 10 %, and 6 %, respectively.