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Abstract The need to reduce the consumtion of energy and the release of CO2 is recognized in the portland cement industry and much effort or resources have been expanded in improving the traditional manufacturing processes. So, there are important needs to resolve the ecological and economical problems to solve ordinary portland cement problems like sulfate and chloride attack. At recylization of solid wastes as GBFS, FA and GCB, these wastes exposed to obtain binder materials characterized by resistance to aggressive media , resistance to thermally tratment temperature, cheaper and more friendly to enviroment than portland cement. Different mixes were prepared from GBBFS, FA and GCB using SH and SSL as alkaline activator. The mixing of the pastes were carried out in a porcelain mortar for 3 minutes with the required amount of water containing the activator untile workability is attained. The pastes were moulded in the 0.5×0.5×0.5 inch moulds and cured in humidifier (100% R.H) at 25oC and 65oC for 3 days then demoulded; and cured in 100% relative humidity upto 360 days. Compressive strength, bulk density, combined water, total porosity and combined slag contents were measured. The hydration products of some selected samples were identified by XRD and SEM technique. For elevated thermally treated temperature, or firing resistance, the specimens cured at 28 days then dried at 100°C for one day, and then exposed to various elevated temperatures at (200°C upto 1000°C) in an electric furnace for two hours, then cooled in furnace closed switch off-to reach room temperature. For Chapter V: Summary and Conclusion 160 aggressive attack, the specimens are stored under water for 28 days (zero month), then subjected to 5% MgSO4 or 5% MgCl2 solution. The specimens are tested at 1, 3, 6, 9 and 12 months. The durability of some selected mixes in aggressive solution such as 5% MgSO4 or 5% MgCl2 upto 12 months was studied. The physicochemical, mechanical and microstructure characteristics of pastes were determined .The effect of aggressive ions was investigated using XRD and SEM techniques. The total chloride and sulphate contents were determined for the immersed samples. from this study the following main conclusions were obtained: 1.physico-chemical and mechanical characteristics 1.1.Alkali Activation of GBFS: The compressive strength gradually increased with the curing period for all hardened mixes, due to higher reactivity of geopolymer slag binder with the formation of successive amounts of calcium silicate hydrates (CSH), calcium aluminate hydrate (CAH) and sodium-alumino-silicate hydrated geopolymer gel (N,C) ASH through the activation process. The data showed that the compressive strength values improved with increasing of the Na2O content and heat-treated temperatures upto 65oC. Mix S4 gives the highest compressive strength values at all curing period. The combined slag of GBFS binders improved with the alkaliactivated content. The values of the BD improved and the TP decreased with treatment temperatures and ages. Chapter V: Summary and Conclusion 161 1.2.Alkali Activation of GBFS-FA: the synergetic effect of alkali activated and thermally treated temperatures improved the performance of GBFS-FA binders. These results proved that the Wn contents of the geopolymer binders enhanced with increase of Na2O content from 0.5 to 1 mol/kg of binder as seen in behavior of SF3 and SF4 mixes. the combined slag contents of alkali activated GBFS-FA are lower than those of GBFS pastes (S1 mix). The combined slag content decreases by replacement of slag by 50% FA due to the dilution of GBFS in the blends. 1.3.Alkali Activation of GBFS-GCB: The results showed that the mix containing 100% GBFS (S1) has higher compressive strength than those of mix containing 50% GBFS + 50% GCB (SH1) at all hydration ages and has a resenable compressive strength values as compared with SH2 by increasing the curing time at 65oC. An increasing in the compressive strength values was observed in the case of replacing GBFS by 50% GCB only in case of SSL mass ratio of 1.0 after all curing ages as shown in mixes SH3 and SH4. Mix SH4 give the highest compressive strength values at all curing period. SEM for geopolymer pastes having 50% GCB (SH4) after 360 days cured at 65oC , is more compact and less pores than 100% GBFS (S1) . The denser structure was observed due to the higher Na2O content in the geopolymer mixture; this enhanced the geopolymerization process and increased the compressive strength. Chapter V: Summary and Conclusion 162 1.4.Alkali Activation of FA-GCB: The results showed that the mix containing 100% GBFS (S1) has higher compressive strength than those of mix containing 50%FA + 50% GCB (HF1 and HF2) at all hydration ages. The data showed that the compressive strength values improved with heat-treated temperatures at 65oC as well as by increasing of the Na2O content upto 1 mol/kg of binder. The combined slag content of the mixes containing GCB+FA (HF) mixes lower than slag geopolymer mix at all hydration time up to 360 days. The combined slag and combined water contents of alkali activated GCB-FA are lower than that of GBFS paste (S4mix). This is attributed to the low activity of FA and homra , espically at early ages of hydration. 1.5.The characteristics of the optimum mixes: S4 mix specimens prepared using the highest content of sodium hydroxide (SSL:SH mass ratio of 1.0mol/Kg), showed the highest compressive strength values at all tested ages in comparison with other mixes. On the other hand all mixes (SH4, SF4, HF4 and S4) have higher compressive strength values than those of S1 mix at all hydration ages. The results also showed that the replacement of 50% GBFS by 50% GCB (SH4) or 50%FA (SF4) give comparable compressive strength values to the S4 mix. Mix S4, which activated and thermally cured at 65oC, showed the highest combined water values than S1 and give a comparable values to SH4 but give higher values than SF4 and HF4. Chapter V: Summary and Conclusion 163 2. Resistance to thermally treated temperatures of alkali activated slag geopolymer: Compressive strength of all specimens enhanced by increasing the elevated treatment temperatures upto 400°C, but when the samples exposed to thermally treated temperature at 600 °C has caused the further strength degradation. On the other hand, the increase of the thermally treated temperatures, upto 800 and 1000oC, an increase in CS was shown due to the sintering process or solid-state reaction to produce a ceramic bond of geopolymer ingredients. The alkali activated slag of mix S4 exhibited the higher values of the bulk density and less values of the total porosity at all treated temperature in comparison with the other mixes. The weight loss showed a sharp significantly increase upto 400°C. This indicates that Ca(OH)2 is not formed in the alkali activation of CaO-rich slag in geopolymers despite very high alkalinity. Further increase in temperature from 800°C to 1000°C, the data showed another increase in the weight loss of the specimen. The weight losses of the geopolymers cured at high temperature (65°C), are greater than the weight losses of the samples cured at (25°C) 3. Aggressive chemical attack: The CS of OPC pastes increased upto 3 months then reduces up to 12 months Mix S4 has a higher values of compressive strength than neat OPC and other mixes, and increased upto 12 months The total sulphate contents are increased upto 12 months for all alkali activated slag binders. OPC pastes give a higher values of the total sulphate and total chloride contents than other mixes. The data showed that SF4 mix represent the higher durability to the Chapter V: Summary and Conclusion 164 penetration of the sulfate and chloride ions attack, leading to formation of a denser structure and enhances the durability to chloride medium upto 12 months. |