Use of environmental friendly recycled aggregate concrete in production of structural members

Water, one of human life's basic living necessities and most important, is the most consumed natural resource by people in the world. The second most consumed resource in the world in terms of consumption, though not as important as water, is concrete. Because concrete is everywhere in our lives. Our homes, schools, hospitals, offices, roads, and more, which we live in and are almost entirely in our lives, have long been produced from concrete. In addition, 80% of mankind lives in concrete and derived structures, the average 20.000-TL expenditure for concrete to be used in making a standard house in our country, 74.000.000.000-Euro expenditure for concrete production in Europe every year, when we think of TL as a 9-TL expenditure in the economy of the country, the importance of concrete is increasing a little more. As the day becomes more and more important for humanity, concrete is destructing the environment and nature with the harmful effects it produces during its production and makes the fields where it is produced unavoidable if necessary environmental precautions are not taken. It is also clear that the necessary measures are not taken during the disposal of concrete, which has completed both the production and the service life, and that this waste concrete will cause non-irreversible damage in the nature unless a proper disposal method is selected. In recent years, although some precautions have been taken to reduce the environmental pollution in concrete production areas, no significant progress has been made in the disposal of concrete that has completed its life cycle. This is because waste concrete, which has completed its life, is considered to be insignificant in many countries that consider concrete production of new materials to be equivalent to economic development, and the disposal of this concrete is done by pouring into the waste areas. This method of disposal, applied in many developed and developing countries, is a method that does not contribute to the environment, to the nature, to the economy, to the collecting and finally to the human. However, as new concrete production and increasing environmental problems caused by waste concrete, traffic problems, natural destruction and sudden decrease in natural resources have started to affect the economies of the countries, it has become inevitable to take measures and solve the related problems. Because developed and developing countries facing economic difficulties need to end waste wastage and recycle them in order to get maximum benefit from the existing natural resources in the long run, it is necessary to develop ways of recycling and reusing wastes to contribute to economy, collecting, environment, nature. If waste materials are recycled and alternative uses for these materials are available, the rapid depletion of limited natural resources will be avoided, economic gain will be ensured, environmental problems caused by construction-based waste will cease to exist, or will decrease. From a different perspective, researching an alternative way for protecting of natural aggregate (NA) resources has been a passionate subject in the past 70 years. These researching studies firstly appeared after the World War2nd in Germany and England, and recycled concrete aggregate (RCA) was initially used in houses and pavement construction (Hansen 1992, Khalaf and DeVenny 2004). At this time RCA is obtained mainly from the waste of the demolished buildings in the ruined cities of Germany and England. In addition, the RCA may contain bricks, brick dust, tiles, metals and other varied materials such as glass, wood, paper, plastic and other wastes along with crushed concrete. After the World War2nd, construction process in war victory countries continues to incearese both to satisfy an enormous demand for building materials and to clean out the building demolition waste from the ruined cities. İn case of using the RCA obtained from the demolition buildings, this situation gave chance not only to reduce site clearing costs, but also to satisfy the demand of building materials. The construction progress has rapidly continued until the end of the 20th century. Although, the wounds of World War2nd have been relieved, construction progress continues to increase for the rapid development of population and urbanization in the countries. The increasing of population and urbanization in the countries has led to construction of new convenient structures and demolishing existing structures reach the end of their service life and inconvenient for the modified seismic codes. Conventionally, as present day of construction sector as in the past, two problems will get to be two more clear to social orders, first an increasing demand for natural aggregate to build new convenient structures, second an increasing production of construction and demolition waste arise from the demolishing of inconvenient old structures. These two clearer problem have become either the cause of natural aggregate extinction at an alarming rate or slowly becoming a challenging problem for sustainability of environment, social orders and economy. For finding sustainable solution both the concern of increasing demand for natural aggregate and increasing production of construction and demolition waste, many countries have started to recycle and reuse the construction waste as in the past, which is used to completely or partially incorporating the NA in new concrete mixtures. In case of applying the solution, it is not only can help to protect and extend the life of natural aggregate resources but also can reduce the cost of waste treatment and the demand on landfill areas for disposing the waste. What is more, the solutions can let the construction sector to diminish its carbon emission and help it to continue to grow without harming the environment and social orders in response to growing environmental, social and economic problems, researchers are looking for efficient, innovative material solutions that protect the NA resources. Increasingly, recycled aggregate concrete is being recognized for its strong environmental, social and economic benefits in support of effective sustainable development. When considering the lifetime environmental impact of a construction material, mining, processing, construction and demolition, recycled aggregate concrete is an important alternative to supply with these aims. For that reasons, lots of experimental and analytical studies have been performed since 1940s in the world for the utilization of recycled concrete aggregate. Our positive perception in the world for the recycling and reusing of waste concrete has been tried to develop the necessary solutions for the problems caused by construction waste concretes in common and these studies are continuing. Within the scope of this doctoral dissertation study, which has been made in order to contribute to ongoing studies, the availability of RCA obtained from low-strength waste concrete in the production of structural elements of concrete structures (Green concrete). In addition, in order for a concrete to be green concrete, it must have certain characteristic properties. These characteristics are: the contribution to the environment will be high, it will be sustainable, it will save on natural resources, so it will contribute economically and it will have to contribute directly or indirectly to the gathering. If you need to make a definition for green concrete from this point, you can make a definition like this. Green concrete; It can be defined as concrete which is resistant to disasters (especially against earthquake), has high energy efficiency, is sensitive to social life and environment, contributes to sustainable development and provides safe and peaceful living spaces. Within the scope of this study, the following studies were carried out respectively. First of all, it was decided that concrete would form a waste concrete source. For this purpose, waste concrete with low strength, known as concrete ages and concrete recipes used in production, was selected. The properties of waste concrete with all known properties vary between 7-16 MPa, and this waste concrete is a structural element exposed to all environmental conditions. After full-scale two-story frames and full-scale columns that make up the waste concrete source are identified, these elements are broken up into small concrete particles by crushing. The waste concrete outside these concrete particles is foreign matter; plastics, steels, glass, metals and wood were hand-cleaned. During this foreign matter removal process, no acid separation method was used. The low-strength waste concrete, which has been cleaned from foreign materials, is then transferred to the trucks and tranferred to the conversion plant. After recycling of waste concrete, 3 different granules, 0-5 mm, 5-12 mm and 12-22 mm diameter recycled concrete aggregate were obtained. These aggregates were not immediately used in concrete production, but firstly, observational and experimental aggregate tests were carried out on these aggregates. As a result of the experimental and observational studies made, aggregate suitable for use in new concrete production was selected and concrete production phase was passed. During the concrete production phase, concrete recipes were prepared to obtain the target concrete strength and test mixtures were made according to these recipes. As a result of the test mixes made, concrete was produced according to the final recipe after determining the recipe to obtain the target concrete strength, and cylinder tests were carried out at 2, 7 and 28 days to determine the compressive strength of the concrete concerned. Cylinder tests showed that the target concrete compressive strengths were obtained. In this small scale material test that is planned to be produced after this stage, preparation of production elements and structural elements production preparations have been started. The structural elements planned to be produced consist of the following. From these elements, 16 one-way-slabs are designed to reach the carrying capacities with the flexural failure. In addition, within the scope of this study, a total of 16 full-scale cantilever columns were designed in total of 10 cantilever columns are designed to reach the carrying capacities with the flexural failure and 6 cantilever columns are designed to reach the carrying capacities with the shear failure. These designed elements were produced considering the details. After these elements were produced, material tests were done first and then structural elements were tested. Experimental data were evaluated after the end of the entire experimental study. Analytical calculations have been made for one-way slabs, flexural critical cantilever columns, and shear critical cantilever columns to look at the analytical fit of these experimental data. Overall results were obtained by evaluating the experimental and analytical study results. In the following, all the work outlined here is explained in detail.