Evaluation of silica-fume effect on the mechanical properties of concrete with fine recycled aggregates

Today, it is quite clear that the speed of development of infrastructure in developing countries has led to much damage to the environment. Concrete is one of the products that plays an important role in the use of non-renewable resources. Today, the vision of sustainable development in the manufacturing industry is growing and increasing, and concrete is at the forefront of this as one of the most widely used construction products. The present study investigates the effect of the use of silica-fume (SF) pozzolan powder on the mechanical properties of recycled concrete made from fine recycled aggregates. Recycled concretes consists of different levels of replacement of fine recycled concrete with natural fines. In order to improve the quality of recycled concrete, Pozzolan was introduced at various levels with cement. To determine and compare the mechanical properties of concrete, 12 mixing designs were made and compressive strength tests at 7, 28 and 91 days, tensile strength, and ultrasound velocity at 28 days of age were performed. The results showed that, generally speaking, in the 28-day period, the use of SF can cause 25% recycled concretes to achieve a desirable 40 MPa strength. The use of 10% SF replacement rate, especially in concrete containing 25% recycled aggregates, made the mechanical properties of recyclable concretes significantly closer to conventional concrete.