Rapid increase in urban infrastructural developments in developing countries such as India leads to the need for natural resources such as river sand. The accessibility of the natural resources is diminishing rapidly. At present, other sources of fine aggregates are in great demand. This work concentrates on the utilisation of weld slag (slag left after the welding process) as fine aggregate in high-performance concrete (HPC) (70 MPa). The chemical and physical characteristics of weld slag aggregate, such as specific gravity, scanning electron microscopic images, X-ray diffraction and energy-dispersive spectroscopy analyses were investigated. Further experiments were conducted by replacing weld slag for fine aggregate in varying percentages (10, 20, 30, 40 and 50%). Fresh concrete properties (slump cone test) and the hardened properties such as compressive strength, split tensile strength, flexural strength, ultrasonic pulse velocity test and the water absorption test were evaluated. The obtained test results indicate that the substitution of weld slag in place of fine aggregates up to 10% is favourable for making HPC without affecting the strength and water absorption. This experimental work proves that the weld slag is the best resource in making concrete, which reduces the disposal of waste leading to an economical and eco-friendly concrete.