Structural performance of RC slabs provided by pre-cast ECC strips in tension cover zone Hamdy Mohy El-Din Afefy ⇑,1 , Mohamed Hussein Mahmoud Structural Engineering Dept., Faculty of Engineering, Tanta University, Tanta, Egypt highlights  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. article info Article history: Received 9 February 2014 Received in revised form 12 April 2014 Accepted 15 April 2014 Keywords: Crack width Cracks spacing Deflection Ductility Engineered Cementitious Composites (ECC) RC slabs Size effect Strengthening abstract 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 perfor- mance in terms of decreased crack width, better crack distribution, and improved capacity and ductility compared to control slabs without internal ECC strips. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Cracking in reinforced concrete structures is inevitable due to the low tensile strength of concrete. Acting loads on the structure results in increased cracks in both width and distribution. Wider cracks, which recommended being in the range of 0.25–0.38 mm [1], for normal condition exposure, not only destroy the aesthetics of the structure but also expose the steel reinforcement to the environment leading to corrosion. Hence, a durability problem maybe encountered. Cracking in reinforced concrete slabs also causes significant increase in deflection. This is a result of the reduction of bending stiffness at cracked sections especially if the effect of tensile concrete below the neutral axis diminishes. However, at sections between successive cracks, some tensile stress is retained in the concrete around steel bars due to the action of bond [2], contributing to the bending stiffness of the slab. This is called the tension stiffening effect. If the tension stiffening effect is neglected, the calculated deflection maybe overestimated by a large proportion. In sum, cracking of concrete can result in a serviceability problem. Hence, enhancement of cracking character- istics for concrete tension zone can relive or prevent not only http://dx.doi.org/10.1016/j.conbuildmat.2014.04.096 0950-0618/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Address: 34 Ahmed Farouk Ali Ezzat, Smouha, Alexandria, Egypt. Tel.: +20 3 4298 793; mobile: +20 106 177 3174. E-mail addresses: hamdyafefy@hotmail.com (H.M.E. Afefy), m_hussein_20@ yahoo.com (M.H. Mahmoud). 1 The experimental work had been conducted at Tanta University’s Concrete and Heavy Structures laboratory. Construction and Building Materials 65 (2014) 103–113 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat