Much of the existing building stock in Europe and developing countries was designed according to old standards using poor material and construction practices. These buildings have deficient lateral load resistance that can lead to extensive damage and collapse during strong earthquakes as observed in recent major events (e.g Haiti 2010, Lorca 2011, Nepal 2015). In the last 15 years, loss of human life due to earthquakes was over 60,000/year with $300 Billion/year estimated economic loss. Deterioration of structural elements due to ageing and aggressive environmental conditions is another factor that can significantly increase the vulnerability of reinforced concrete (RC) structures. The retrofit of deteriorated or seismically deficient structures provides a feasible and economic approach to improving their load carrying capacity and reducing their vulnerability. Different conventional retrofitting techniques have been examined in the past to enhance the performance of substandard structures. However, these methods can be highly invasive, labour intensive and they usually increase the mass of the building. In recent years, the use of composite materials in retrofitting of existing structures has been increased substantially and proved to be efficient in accommodating deterioration of structural elements or damages observed after strong earthquakes. Externally bonded Fibre Reinforced Polymers (FRP) applications have gained ground due to the advantages such as high resistance to corrosion, excellent durability, high strength to weight ratio and adaptability of the technique to different types of structural members. However, high initial cost of FRP materials and their fire protection requirements are major obstacles to their wide application, especially in developing countries. Therefore, there is a pressing need to develop more cost-effective retrofitting solutions for substandard structures. This action aimed to develop a novel and economic method for strengthening of substandard RC structures by using a new generation of environmentally friendly mortar-based composite materials using recycled high strength steel cords/fabrics embedded in an inorganic grout matrix. This novel technique can be efficiently used for flexural, axial and shear strengthening of reinforced concrete (RC) members and it is cost effective, fire resistant, sustainable, and has low environmental impact. The main objectives of the project is to: (i) develop a better understanding of the characteristics of mortar-based composite materials with inorganic matrix and bond-slip behaviour between steel cords and grout to develop design-oriented models for the novel strengthening system; (ii) develop design-oriented models and performance-based design guidelines so that this new technique can be introduced in practice; (iii) evaluate analytically the efficiency of the novel strengthening system at improving the seismic performance of representative substandard buildings through non-linear time-history analyses; and (iv) develop practical design guidelines for adoption by European standards to use the new technology for strengthening of deficient RC members.