الفهرس 
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Abstract
Concrete manufacturing is thought to be a substantial contribution to global warming, due mainly to the usage of Portland cement as a binding element. The cement sector is estimated to be responsible for 8% of global CO2 emissions. To lessen the environmental impact of concrete manufacturing, efforts to develop alternatives to Portland cement are still ongoing. Alkali-activated material, a new environmentally friendly inorganic binder created by activating alumino-silicate source material (such as slag, fly ash, and metakaolin) with an alkaline solution, has received substantial attention in recent years as a practicable alternative to Portland cement. In addition to making optimal use of industrial byproducts, utilizing alkali-activated material as a binder minimizes greenhouse gas emissions, CO2 emissions, and energy needs during production.
Numerous studies have been conducted in recent years to improve the strength of geopolymer products, investigate the fresh and hardened characteristics of geopolymer, and comprehend the mechanism of geopolymerization. When choosing geopolymers as repair materials, the bond strength between the substrate concrete and the repair material is critical. Because the majority of these tests were conducted on paste and mortar rather than concrete, further research is needed before geopolymer concrete may be used as a retrofitting material.
The main goal of this experimental study is to investigate the bond behavior between geopolymer concrete and substrate Portland cement concrete (PCC) for various levels of constituent materials and surface preparation techniques, as well as to investigate the flexural behavior of reinforced PCC slabs retrofitted with geopolymer concrete layer.
Three main phases are included in this research work:
The first Phase: examined the mechanical and physical characteristics of employed ambient cured GPC mixes containing two types of aluminosilicate source binders: ground granulated blast furnace slag (GGBFS) and fly ash (FA). During this phase, the mechanical and physical characteristics of the PCC mix were also investigated in order to study the compatibility between PCC as a substrate layer and GPC as a potential retrofitting layer and the effect of varying parameters on the bond strength between the two layers. GPC maintained better compressive strength at the same binder content, according to test results. GPC also performed well in terms of coefficient of thermal expansion (CTE) and drying shrinkage, with lower (CTE) and lower drying shrinkage than PCC. In contrast to compressive strength, GPC showed lower flexural strength, indirect splitting tensile strength, and modulus of elasticity than PCC. At the microstructure scale, the unsatisfactory behavior of GPC in tension was related to crazing micro cracks that developed in the paste and at the interfacial transition zone (ITZ) between paste and coarse aggregate.
The Second Phase: carried out to test the bond strength between GPC mixes as a repair layer and PCC mixes as a substrate layer using two surface preparation roughening techniques, sand blasting and manual. There were two bonding agents used, one with epoxy-based material and the other with cement-based material. The bond strength between GPC and PCC was evaluated using slant shear and pull off tests. The use of a manual roughening technique and a cement-based bonding agent improved the bond strength between two layers, according to the findings of the tests.
The Third Phase: carried out to assess the flexural behavior of reinforced PCC slabs reinforced with a GPC layer. Two large RC slabs were created. One specimen was retrofitted with slag-based GPC, while the other was retrofitted with PCC similar to the substrate slab. The compression face of the substrate slabs attained both strengthening layers. The same interface treatment technique for the RC substrate surface was used for both slabs which was the technique that gave better results in phase II during the evaluation of bond strength. The cracking capacity, ultimate capacity, deformation features, strain profile, and failure modes of RC retrofitted slabs were assessed. The slab retrofitted with GPC had a slightly greater failure load, higher deflection, lower cracking height, and higher compression strain than the slab reinforced with PCC. In the two retrofitted slabs, no interfacial slippage was observed.
Keywords: Geopolymer concrete, Alkali Activated Concrete, Alkali Activation, Mechanical characteristics, Physical characteristics, Bond Behavior, Surface Preparation, Compatibility.