الفهرس 
Introduction, and Literature SurveyOnly 14 pages are availabe for public view
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Abstract
Geopolymer is regarded as an encouraging sustainable and environmentally favorable material substitute to Portland cement in construction applications. Portland cement generation increments worldwide greenhouse gas emissions outflows through the calcination of clinker in hydrocarbon warmed heaters. Generally, a decrease in cement utilization has been accomplished by the utilization of industrial by-products, for example, fly ash (FA), and ground granulated blast furnace slag (GGBFS) as partial or complete replacement materials to Portland cement in concrete.
Various mixes are prepared using different liquid/solid ratio (L/S) by weight. Sodium hydroxide pellets (SH) with commercial sodium silicate liquid (SSL) are used as activator that is dissolved in the mixing water. After complete mixing, the resultant pastes are molded into specimens using one-inch cubic moulds then cured under relative humidity 100% for 24 hours. The specimens are removed from the moulds and cured under relative humidity 100% for different time intervals, namely; 2, 7, 28, 56, and 90 days. Some cubes are immersed (after 28 days curing under relative humidity 100%) in 5% MgSO4 solution for different time intervals up to 90 days.
The hydration characteristics of the different mixes have been tested via determination of compressive strength, total porosity, combined water, bulk density, and XRD analysis at different time intervals, to study the effect of some artificial pozzolana such as ground granulate blast furnace slag (GGBFS), Cement kiln by-pass dust (CKD), Silica fume (SF), and Fly ash (FA) on Geopolymer composition and its resistance to sulphate attack.
The main conclusions could be derived from this investigation are summarized as follows
1- Alkali Activation of GGBFS
• Alkali activation of alumino silicate materials considered as a complex process that has not been described to the full yet. The reaction of alumino silicate materials in a strong alkaline environment results, first, in a breakdown of Si–O–Si bonds; later, new phases arise and the mechanism of their formation seems to be a process that includes a solution (”synthesis via solution”).
• By using the comparison of alkali-activated slag (AAS) with the ordinary Portland cement (OPC) it showed that there are significant differences in the hydration mechanisms between them. The calcium silicate hydrate (C-S-H) phase – a main hydration product in both systems – shows different precipitation mechanism.
• The formation of C-S-H is much faster in AAS and it precipitates directly into the pores of solution filled spaces which result in a voluminous gel-like(C-S-H) phase. This fact shows the relatively fast early strength development in the AAS system compared to the OPC.
2- Activation by Commercial sodium silicate liquid
• Various mixes S1, S2, S3, S4, S5 and S6 are prepared using different liquid/solid ratio (L/S) by weight. Sodium hydroxide pellets (SH) with commercial sodium silicate liquid (SSL) are used as activator which dissolved in the mixing water.
• The combined water contents of the alkali activated GGBFS pastes gradually increases up to 90 days. This is due to the continuous hydration of hydrated products, which deposed in the available open pores.
• Mix S6 (15 % SSL, and 15 % SH) shows the higher values of compressive strength during all curing ages of hydration. As the amount of alkali activator increases, the compressive strength enhances and develops.
• The bulk density of alkali activated GGBFS increases with curing time this due to the continuous activation and formation of hydrated products. These hydrated products are deposited in the open pores that explains the increase in the bulk density of the activated slag.
• X-ray diffraction patterns for different mixes 100 % GGBFS showed the presence of C-S-H phase that formed during the hydration reaction, which is mainly responsible for the good distinct strength of GGBFS.
3- Alkali Activation of GGBFS – CKD
• Various mixes SC1, SC2, and SC3 are prepared using different liquid/solid ratio (L/S) by weight. Sodium hydroxide pellets (SH) with commercial sodium silicate liquid (SSL) are used as activator which dissolved in the mixing water.
• The combined water contents of the alkali activated (GGBFS) pastes gradually increases up to 90 days. This is due to the continuous formation of hydration products, which deposed in the available open pores. Which make the total porosity decrease and as a result of this the compressive strength increase.
• Using 10% CKD (mix SC1) is the optimum ratio for geopolymer formation and activation of GGBFS by (15% SH, and 15% SSL) this specimen’s exhibit high resistance to sulfate attack as there is little deterioration up to 90 days of exposure in 5% MgSO4 solution. While further increase of CKD content leads to decrease in the mechanical characteristics of the reaction products. This is mainly attributed to the presence of large amounts of alkalis in the form of chloride and sulphate that causes a sort of crystalline hydrated products resulting in an opening of the pore system and so leads to lower the mechanical properties (Khater, 2013) & (Al-Faluji et al., 2021)
4- Alkali Activation of GGBFS – SF
• Various mixes SS1, SS2, and SS3 are prepared using different liquid/solid ratio (L/S) by weight. Sodium hydroxide pellets (SH) with commercial sodium silicate liquid (SSL) are used as activator which dissolved in the mixing water.
• The combined water contents of the alkali activated GGBFS pastes gradually increases up to 90 days. This is due to the continuous formation of hydration products, which deposed in the available open pores. Which make the total porosity decrease and as a result the compressive strength increase.
• Silica fume addition up to 15% (mix SS2) greatly enhances the geopolymerization process with the formation of a well-refined and compact matrix, where silica fume represents an enrichment source of amorphous silica and enhancing geopolymerization. While further increase of SF content leads to decrease in the mechanical characteristics of the reaction products.
5- Alkali Activation of GGBFS – FA
• Various mixes SF1, SF2, and SF3 are prepared using different liquid/solid ratio (L/S) by weight. Sodium hydroxide pellets (SH) with commercial sodium silicate liquid (SSL) are used as activator which dissolved in the mixing water.
• The combined water contents of the alkali activated GGBFS pastes gradually increases up to 90 days. This is due to the continuous hydration and accumulation of hydrated products, which deposed in the available open pores. Which make the total porosity decrease and as a result the compressive strength increase.
• Mix SF2 (85% GGBFS, and 15% FA) shows the higher values of compressive strength at all curing ages of hydration. It is clear that the values of the compressive strength increase are due to the higher rate of hydration as well as formation of more hydrated products. As the amount of Fly ash (FA) increase the compressive strength of hardened alkali activated GGBFS cured up to 90 days increase also, and give high durability to the paste. But further increase of FA content leads to decrease in the mechanical characteristics of the reaction products.
6- Resistance to Magnesium sulphate attack:
• All mixes show high stability on its compressive strength values in 5 % MgSO4 solution. Due to a good pozzolanic activity in alkaline activation which exhibits higher resistance to sulphate medium up to 90 days. The immersion of alkali activated GGBFS pastes in 5% MgSO4 solution enhances the activity of GGBFS pastes.
• The compressive strength of alkali activated GGBFS as well as OPC immersed (after 28 days curing under relative humidity 100%) in 5% MgSO4 solution up to 90 days are studied, and it is clear that the compressive strength of OPC increases up to 7 days then decrease gradually due to the formation of expanding and softening ettringite hydrated products.
• The resistance towards sulphate attack solution increases with the increase of alkali activated contents. This is mainly due to the decrease of the total porosity which hinders the penetration of sulphate ions in the matrix, this can be attributed to the fact that the alkali activated GGBFS do not have free lime content in its matrix.
Finally all mixes show good stability on its compressive strength values in 5 % MgSO4 solution. Due to a good pozzolanic activity in alkaline activation that exhibits higher resistance to sulphate medium up to 90 days. The immersion of alkali activated GGBFS pastes in 5% MgSO4 solution enhances the activation of GGBFS pastes.
After studding the effect of some artificial pozzolana on geopolymer composition and its resistance to sulphate attack, the data showed that mix SF2 (85% GGBFS, and 15% FA) activated by (15 % SSL, and 15 % SH), and mix S6 (100% GGBFS) activated by (15 % SSL, and 15 % SH) are the most appropriate binding materials (geopolymer cement) that have a good different properties that can be used as alternative binding material to the ordinary Portland cement.