الفهرس 
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Abstract
Utilization of concrete as a major construction material is a worldwide phenomenon and the concrete industry is the world’s largest consumer of natural resources. Cement is usually used as a binder in concrete mixtures. The use of concrete is driving the massive global production of cement which is estimated to be responsible for 5 to 7% of the total global production of carbon dioxide. Furthermore, the concrete industry’s extraction of raw materials has a negative impact on the environment. On the other hand, every year, a massive amount of construction and demolition waste is generated. This waste is typically disposed of in landfills or illegally dumped. The disposal of this waste is a significant social and environmental issue. Thus, finding new eco-friendly construction materials for green and sustainable construction is very essential. In this study, the geopolymer concrete (GPC) produced with recycled Portland cement concrete aggregate (RCA) as a coarse aggregate will be investigated as a construction material. The GPC can be employed as an eco-friendly, sustainable construction material, as it does not use Portland cement in its production. In addition, using the RCA in the production of GPC will promote sustainability and save natural resources. There is a lack of research which investigates the integration of the RCA into the GPC. Thus, in this study, the fresh, hardened, and durability properties of the GPC that are produced with RCA will be investigated and compared to the same properties of traditional Portland cement concrete. The current research presents an experimental study to investigate the influence of using recycled Portland cement concrete as a coarse aggregate on the performance of II a fly ash based geopolymer concrete. Geopolymer mixtures with different replacement percentages by volume of recycled coarse aggregate were used. Two types of recycled concrete aggregates with maximum grain sizes namely 10 and 25 mm were investigated with 0, 20, 40, 60 and 100% as a replacement for the natural aggregate (NCA) by volume. The used binder was a mixture of fly ash and alkaline solution and the alkaline solution to FA ratio was (0.45), the used alkaline solution composed of sodium hydroxide with 12 molar concentration as well as sodium silicate. The sodium silicate (NS) to sodium hydroxide (NH) ratio was (2.5). After mixing and casting, the GPC samples were left open at room temperature for 24 hours. They were then heat cured in an oven at 65°C for 48 hours. The conducted mixes were studied to evaluate the effect of the investigated parameters on physical, mechanical as well as the durability characteristics. The investigated physical properties included the consistency of fresh mixes evaluated with flow test. On the other hand, unit weight, compressive strength, splitting tensile strength, flexural strength, and bond strength were evaluated as mechanical properties. Moreover, durability characteristics including water permeability, sulfuric acid attack, exposure to elevated temperatures, chloride ion penetration, and accelerated corrosion tests were conducted. The results show that the consistency of the studied mixtures reduced with the increase of the replacement ratio. The GPC also had lower consistency than OPC. Moreover, the compressive strength values of both OPC and GPC were increased slightly at the replacement ratio of 20% NCA by RCA at all ages. However, at higher replacement levels, the compressive strength decreased at all ages. On the other hand, the GPC achieved higher strength for all mixes compared to the OPC. The other hardened strengths (indirect tensile strength, flexural strength, and bond strength) were decreased with the increase in the replacement ratio at all ages. Also, the results show that GPC achieves higher strengths for all mixes. III The GPC specimens achieved a lower water permeability value than the OPC specimens at all replacement levels, and with increasing the RCA content, the water permeability values were increased for both GPC and OPC. The GPC exhibits excellent resistance against elevated temperatures up to 1000 °C as compared to OPC concrete with regard to residual compressive strength, mass loss, physical appearance, surface cracking, and spalling. The GPC specimens exhibited better corrosion resistance and yielded a longer time to failure than the OPC specimens at all replacement levels, and the increase in the RCA ratio has an adverse effect on the corrosion resistance of both GPC and OPC. The GPC exhibits excellent resistance against acid attack as compared to OPC concrete, while the increasing in RCA content has an adverse effect on the mass loss and the residual compressive strength of both GPC and OPC samples. At all replacement levels, GPC specimens showed a higher resistance against chloride penetration than OPC specimens at all replacement levels, while the increase in RCA content led to a higher chloride penetration depth. Finally, the results indicated that the recycled Portland cement concrete may be used as a coarse aggregate in producing structural Geopolymer concrete with comparable properties, which can make the construction industry a more sustainable process. Outline of the Thesis The contents of thesis are presented in six chapters. A brief description of each chapter is given as follows: Chapter (1): Introduction This chapter includes an introduction defining the problem, aim of the proposed work and thesis outline. Chapter (2): Literature review This chapter presents a literature review for the theoretical and experimental studies related to the current search. IV Chapter (3): Experimental investigation Reports on the data of the experimental test program, the properties of the materials used, and the description of tests set up and test procedure. Chapter (4): Fresh and hardened test results and discussion In this chapter, the experimental results of fresh and hardened properties for GPC and OPC are presented and analyzed to explore the influence of different replacement ratios of RCA on fresh and hardened properties of both GPC & OPC. Chapter (5): Durability test results and discussion In this chapter, the experimental results of durability properties for GPC and OPC are presented and analyzed to explore the influence of different replacement ratios of RCA on durability properties of both GPC & OPC. Chapter (6): Conclusions and Recommendations This chapter presents the conclusions and Recommendations from the experimental results. Suggestions for the future work are also presented.