الفهرس 
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Abstract
Fly ash based geopolymer concrete (GPC) is an eco-friendly concrete made from alkali activated aluminosilicate and aggregate. Generally, geopolymer concrete needs several approaches before and after casting which limits its in-field applications. Development of geopolymer concrete becomes a demand to widen its application beyond precast concrete. Scientific investigation on geopolymer concrete domain was worthy of attention over the last two decades. Studies contend that geopolymer concrete has better mechanical and durability properties than conventional ordinary Portland cement concrete at ambient conditions. There are several situations where concrete is prone to elevated temperatures exposure, which require a good understanding of the concrete behaviour under these circumstances. Despite the abundance of information about the behaviour of traditional OPC concrete at elevated temperatures, there is paucity of studies that are related to GPC behaviour after elevated temperatures exposure. This study intends to examine the influence of alkaline solution constituents represented in sodium hydroxide solution molarity, alkaline solution to fly ash ratio and sodium hydroxide to sodium silicate ratio on fly ash based geopolymer concrete properties at ambient conditions and after elevated temperature exposure. Also, a study of the impact of curing characteristics in terms of curing period and curing temperature on GPC properties was provided for unexposed concretes and for those that underwent elevated temperature exposure. Effects of additional water content, fly ash content and cement content as a replacement for fly ash on GPC properties were also studied for unexposed and exposed concretes. Another noteworthy is that altering furnace exposure temperature, cooling regime and duration of exposure have been investigated. The evaluated properties of (GPC) were workability, compressive strength, and flexural strength. Also, microstructural characterization was assessed using scanning electron microscopy technique (SEM). The study results show that, generally, adding cement improves all fly ash based geopolymer properties except workability under unexposed conditions, while for exposed conditions; the increase in cement affects negatively the strength. The increase of fly ash content enhances geopolymer concrete properties. Geopolymer concrete properties significantly affected by curing approaches represented in curing time and temperature. The study also show that, generally, increasing additional water content increased workability, but decreased other fly ash based geopolymer properties and the optimum dose of additional water content was found to be 30 kg /m3 which has slight effect on geopolymer properties. The increase in furnace temperature up to 400ºC has ameliorated concrete properties, yet beyond 400ºC, concrete deteriorates. The optimum molarity of sodium hydroxide solution was found to be 16 M. Geopolymer concrete properties significantly affected by alkaline solution to fly ash ratio and 0.40 was expected to be the optimum ratio. Increasing sodium hydroxide solution to sodium silicate solution ratio reduces geopolymer concrete properties; nevertheless, low ratio is not economic due to sodium silicate solution cost. It was demonstrated that air cooling is better than water cooling in terms of strength. The increase in specimens’ retention time inside furnace during elevated temperature exposure has resulted in a decrease in strength. It was concluded that GPC has superior properties and advantageous over OPC concrete at elevated temperatures.