Assessment of the Efficiency of Eco-Friendly Lightweight Concrete as Simulated Repair Material in Concrete Joints

The high production of carbon dioxide from concrete cement manufacturing and the high utilization of natural resources in concrete has been a concern for research in recent decades. Eco-friendly concrete (Eco-Con) is a type of concrete that uses less energy in its production, utilizes waste materials, produces less carbon dioxide, and is durable. This study assesses the efficiency of the proposed lightweight Eco-Con mixes with 32 MPa compressive strength in repairing different types of concrete structures. Rubber and lightweight expanded clay aggregate (LECA) were used as lightweight materials in the Eco-Con mixes. One Portland cement concrete mix (CC) and three different Eco-Con mixes, namely geopolymer rubber concrete (GR), geopolymer LECA concrete (GL), and rubber-engineered cementitious composite (RECC), were produced and compared. The concrete mixes were utilized as simulated 'repair' materials in several types of concrete joints, namely reinforced slab-beam joints (400 x 300 mm L-shape, 500 mm width, and 100 mm thickness) subjected to bending, concrete joints in beams (100 x 100 x 350 mm) subjected to bending, and concrete joints in unconfined and fiber-reinforced polymer (FRP) confined columns (100 mm diameter and 200 mm height) subjected to axial compression. The reinforced slab-beam joint and FRP-confined column joint were tested with two joint angles of 0 degrees and 45 degrees. The results indicated that RECC is an efficient lightweight Eco-Con alternative to Portland cement concrete in repairing concrete structural elements, especially beams and FRP-confined columns, as it increased their strength capacities by 43% and 190%, respectively. At the tested joint angles (0 degrees or 45 degrees), the use of Eco-Con mixes showed relatively lower slab-beam joint strength capacity than that of the CC mix by up to 14%. A joint angle of 45 degrees was better than 0 degrees, as it showed up to 7% better slab-beam joint strength capacity. Using shear connectors in slab-beam joints had adverse effects on concrete cracking and deformability.