Structural performance of RC slabs provided by pre-cast ECC strips in tension cover zone

• The adopted strengthening technique manifested enhanced capacity and ductility.
• Reinforced ECC strips showed better effect than the plain ECC strips.
• Reinforced ECC strips enabled the slab to exhibited better crack distribution.
• Major crack width decreased significantly due to the provided ECC strips.
• Size effect is significant factor on the experimental crack width and crack spacing.

Pre-cast and cured Engineered Cementitious Composites (ECC) strips were placed in the tension cover zone of one-way reinforced concrete (RC) slabs beside the main steel reinforcement. Using pre-cast and cured ECC mitigates issues associated with volumetric changes associated with the ECC material. In order to assess the structural performance enhancement of the new hybrid system, four point bending tests were performed on two different sizes of RC slabs. The tested slabs were geometrically similar in thickness but and differed in their width and span. Small, 300 mm wide × 900 mm long, slabs were strengthened using one 150 × 500 × 20 mm ECC strip. Larger, 300 × 2000 mm slabs were strengthened with two 150 × 1600 × 20 mm ECC strips. A small amount of conventional reinforcing steel was provided inside the ECC strips in order to enhance the strain hardening behavior of the ECC strengthening strip, and thereby increase its efficiency. The structural evaluation of the slabs considered crack width and spacing, deflection at the service load level, and ultimate capacity and ductility. Test results showed that the ECC strips enhanced the structural performance of the slabs at both service and ultimate limit states. Providing additional internal reinforcement by a reinforcing ratio of 1.88% exhibited outstanding performance in terms of decreased crack width, better crack distribution, and improved capacity and ductility compared to control slabs without internal ECC strips.