Reinforcement of the reinforced concrete slab with reinforced shotcrete concrete

Abstract

Today, there is a significant need to restore, repair, and strengthen concrete and reinforced concrete structures. The composite action of the existing reinforced concrete structure and the newly applied reinforced concrete layer plays a crucial role in the load-bearing capacity of strengthened or repaired building structures. Experience in performing repair and strengthening works on reinforced concrete structures confirms that shotcreting technology is one of the most effective and reliable methods for applying protective coatings to concrete surfaces, correcting concrete defects, and reinforcing concrete and reinforced concrete structures. The study aimed to experimentally evaluate the bond strength between the “old” concrete of the slab and the “new” reinforced shotcrete, and to compare the obtained bond parameters with the design values. Additionally, the study aimed to identify the factors influencing bond strength during the strengthening of a monolithic slab using reinforced shotcreting. According to the design calculations, the damaged reinforced concrete slab was strengthened with No. 10 A500C mesh with a 200×200 mm spacing and shotcrete applied using the dry-mix “Kimtek” technology. The tensile strength and adhesive bond strength of the shotcrete applied to the slab were evaluated using an adhesion tester. Control cubes with a shotcrete layer applied were also produced and tested under laboratory conditions.

The experimental studies showed that the bond strength between the concrete slab layer and the shotcrete was 2–3 times lower than the design values. Therefore, it became necessary to identify technological factors under real production conditions that affect bond strength when strengthening a monolithic slab with reinforced shotcrete, and to account for these factors during the execution of the work.