Investigation of silica fume on mechanical and physical properties of recycled aggregates concrete

Natural resources is decreasing day by day due to the rapid population growth resulting in change in consumption habits which comes unconsciously. Existing limited natural resources are in danger of running out in case recycling can not be achieved and the associated methods are not applied properly. The fact that the needs are increasing each passing day while the natural resources are running out has turned the recycling issue into a very significant topic. Pollutant effluents cause serious environmental problems as air, water and soil pollution. Recycling of these wastes will both reduce the environmental damage and decrease the use of natural resources. Thus, it is essential to recycle the generated effluents as much as possible. Recycling means providing the waste materials -named as pollutant effluents to be reused. With the implementation and improvement in recycling, it would be possible to preserve the natural resources, decrease the pollutant effluents and achieve financial advantages. Recycling is a necessity for sustainable development. The rapid consumption of natural resources has necessitated the recycling. In the construction sector, the idea of reusage of recycled aggregate in concrete production is beneficial in terms of both environmental and financial aspect. Researches are conducted to extend the use of recycled aggregate throughout the world. A great number of recycling facilities have been established in developed countries. In our country, the aggregate, which is one of the main components of concrete, is in short supply due to the rapid consumption of existing limited natural resources and urban sprawl. It is observed that the general layout of buildings is in poor condition in our country in terms of earthquake resistance. This is the reason why a great number of big scale urban transformation projects have been conducted in recent years. The reuse of construction wastes provides both the wastes to less damage the nature and decrease the use of natural resources. In this study, in which the usability of recycled aggregate in the production of concrete has been investigated, natural coarse aggregate used in the production of conventional concrete is replaced with the recycled aggregate, at the rates of 0% and 100%. The physical and mechanical tests were performed on obtained concrete specimens at 7 th, 28th , and 90th days. The silica fume was used as mineral additive at the rates of %0, %5 and %10. The concrete with natural aggregate was produced with water/cement ratio 0.50, 380 dosage, C30/37 target strength according to XS1 exposure class. As to the recycled aggregate, the conventional concrete was crushed with a jaw crusher, then waterlogged, and finally, recycled concrete series were achieved with the same gradation and workability of natural aggregate concrete. Before the production of recycled concrete; unit weight, specific gravity, water absorption, Los Angeles abrasion tests were performed on the recycled aggregate. Having the same mixture ratios, the comparing process of the concrete produced by natural aggregate with the concrete produced by recycled aggregate, was examined by the tests of: unit weight, workability (slump), air content and slump loss in fresh concrete and saturated bulk density, compressive strength, splitting tensile strength, modulus of elasticity, ultrasonic pulse velocity, capillary water absorption and absorption water by volume in hardened concrete and pullextraction strength for reinforced concrete. Keywords: Concrete, sustainability, recycled aggregate, physical and mechanical properties of recycled aggregate concrete