الفهرس 
Introduction and Object of InvestigationOnly 14 pages are availabe for public view
 |  | from | 252 |  |  |
| | | from | 252 | | |
Abstract
Ordinary Portland cement (OPC) manufacture causes severe problems for the economy and environment due to the emission of a large amount of CO2 and high energy consumption during its production. Alkali-activated materials (AAM) or geopolymer (GP) is considered an ideal solution for the OPC production problems, since is prepared by full replacement of OPC with industrial waste material (aluminosilicate material) such as ground granulated blast furnace slag (GGBFS). Ground granulated blast furnace slag is a waste material of iron production containing silica and alumina oxides, which are activated with an alkaline solution (sodium hydroxide) to produce alkali-activated slag (AAS). Alkali-activated slag (AAS) presented good mechanical properties and thermal resistance compared to OPC.
Nanotechnology has shown great potential in different applications that widely used in our life. Nanotechnology presents novel applications in different fields. One of these applications is nanoparticles incorporation in cementing materials to produce new nanocomposites having high performance, such as fire resistance, self-cleaning, and surface coating. Different prepared nanomaterials such as hematite nanoparticles (α-Fe2O3), chromium oxide nanoparticles (Cr2O3), zirconia nanoparticles (ZrO2) and copper oxide nanoparticles (CuO) are added to AAS to improve the mechanical properties, thermal and radiation resistance. In addition, the inclusion of nanomaterials in AAS showed a high performance towards gamma ray shielding and antimicrobial activity.
In this investigation different pastes were prepared by mixing ground granulated blast furnace slag (GGBFS) admixed with 0, 0.25, 0.5 and 1% of each of HPNs, CrNPs, ZrNPS and CuNPs with activated alkaline solution (5% of sodium hydroxide). The compressive strength values of the prepared pastes were evaluated after 1, 3, 7, 28 and 90 days of curing at 100% humidity at room temperature as well as for the hardened specimens (cured for 28 days) after fired at 200, 400, 600 ang 900oC and cooled by two modes (slow and rapid) . The bulk density of some selected hardened composites was evaluated after 7 and 90 days of curing. In addition, the resistance of the hardened specimens made from ASS-HPNs composites against different doses (1000, 2000 and 3000 KGy) of radiation was determined. While, in case of specimens made from AAS-CrNPs, AAS-ZrNPS and AAS-CuNPs composites their shielding efficiency against gamma-ray radiation produced from two different gamma-ray sources (Co-60 of high intensity and Cs-137 of low intensity) were evaluated. The antimicrobial activity for all the hardened samples (after 28 days of curing) was investigated against different microorganisms, particularly two bacteria (Escherichia coli-ATCC 8739 and Staphylococcus aureus-ATCC 6538) and two fungi strains (Aspergillus flavus and Mucor circinelloide) using agar diffusion method. Additionally, the formed phases and morphological features of some selected composites were characterized using X-ray diffraction (XRD), differential thermogravimetric analysis (TGA/DTA), Fourier transform infrared (FTIR), and scanning electron microscope with energy dispersive X-ray (SEM/EDX).
The findings of this investigation are summarized in four sections as follows:
Part A: Physicochemical properties and different applications of the AAS samples admixed with different doses of hematite (α-Fe2O3) nanoparticles (HNPs).
The following conclusions are derived from the obtained results in this part:
1. Specimens prepared from different composites (AAS-0.25HNPs, AAS-0.5HNPs and AAS-1HNPs) presented high compressive strength values compared to the control sample (AAS). This result is attributed to the vital role of hematite nanoparticles in the progress of the hydration/activation process of slag.
2. Specimens made from AAS-0.25HNPs composite showed the highest compressive strength values compared with other nanocomposites and control sample (AAS).
3. Specimens made from AAS-0.25HNPs composite indicated the highest bulk density compared to the control sample, these results confirmed the compressive strength test results.
4. All AAS samples admixed with different ratios of HNPS have good thermal resistance compared to the control sample. AAS-0.25HNPs exhibited the highest compressive strength values after being fired at different temperatures (200, 400, 600 and 900°C) and cooled with two cooling regimes (gradual and rapid cooling).
5. AAS samples containing different ratios of HNPs showed high resistance against various doses of gamma-ray radiation (1000, 2000 and 3000 KGy) compared to the control sample.
6. Specimens made from AAS-0.25HNPs composite exhibited the highest compressive strength values after exposure to different doses of gamma-ray radiation compared to all other specimens and control sample (AAS).
7. The inclusion of different percentages of HNPs within the AAS matrix induced high antimicrobial activity against different types of microorganisms compared to the control sample. AAS-1HNPs composite give the highest antimicrobial activity against all the fungi and bacterium types, especially for Staphylococcus aureus (ATCC 6538) compared to all other composites.
8. Differential thermogravimetric analysis curve (TGA/DTA) of the AAS-0.25HNPs composite showed the highest weight losses percentages after 28 days of curing compared to all other composites and control.
9. X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis for AAS-0.25HNPs composite after 28 days of curing exhibited relatively higher peaks and vibration bands intensities compared to all other tested composites. These findings agreed with the compressive strength test results.
10. Scanning electron microscope (SEM) image for AAS-0.25HNPs after 28 days of curing showed more dense structure compared to the control sample (AAS) due to the formation of an extra amount of hydration products such as CSHs and CASHs.
11. The SEM image of AAS-0.25HNPs specimens after fired at 200°C and cooled slowly indicated a dense structure compared to that of AAS sample after normal curing for 28 day or after fired at 200°C.
12. After firing AAS-0.25HNPs and AAS samples at 900°C their SEM images indicated the existence of large cracks along their microstructure, which ascribed to the deterioration of all binding phases.
13. The SEM images for the AAS-0.25HNPs and AAS sample showed the same microstructure features when exposed to the same radiation dose, but with a denser structure for the AAS-0.25HNPs sample that resists the appearance of cracks formed in the AAS sample.
Part B: Physicochemical properties and different applications of the AAS samples admixed with different doses of chromium oxide (Cr2O3) nanoparticles (CrNPs).
Based on the results obtained in this part, the following conclusions could be derived:
1. Specimens made from different composites (AAS-0.25CrNPs, AAS-0.5CrNPs and AAS-1CrNPs) showed high compressive strength values compared to control (AAS). This result is attributed to the fundamental role of chromium oxide nanoparticles in the progress of the hydration/activation process of slag.
2. AAS-0.5CrNPs composite presented the highest compressive strength values compared with other nanocomposites and control (AAS).
3. AAS-0.5CrNPs specimens showed the highest bulk density compared to the control sample (AAS), this result confirms and agreed with the compressive strength test results.
4. All AAS samples incorporated with various quantities (0.25, 0.5 and 1%) of CrNPS showed good thermal resistance performance compared to the neat AAS. AAS-0.5CrNPs specimens exhibited the highest compressive strength values after being fired at different temperatures (200, 400, 600 and 900°C) and cooled with two different cooling regimes (gradual and rapid cooling) compared with all other tested specimens.
5. All AAS- CrNPs composites exhibited high shielding efficiency (i.e. high linear attenuation coefficient values) to gamma-ray radiation of different sources (Co-60 of high intensity and Cs-137 of low intensity) compared to the control (AAS).
6. All the composites exhibited linear attenuation coefficient values at a low-intensity gamma ray higher than that at a high-intensity gamma ray.
7. AAS-0.5CrNPs composite exhibited the highest linear attenuation coefficient value after exposure to different gamma-ray sources compared to all the composites and control sample (AAS).
8. The inclusion of different percentages (0.25, 0.5 and 1%) of CrNPs in AAS matrix induced high inhibition efficiency against the growth of different types of microorganisms compared to the control sample. AAS-1CrNPs composite showed the highest antimicrobial activity against some microorganisms (bacteria and fungi), especially for Aspergillus flavus compared to all the composites.
9. Differential thermogravimetric analysis curve (TGA/DTA) of the AAS-0.5CrNPs specimens showed the highest weight losses percentages after 28 days of curing compared to all composites and control.
10. Scanning electron microscope (SEM) image for the AAS-0.5CrNPs specimens after 28 days of curing showed more dense structure compared to the control (AAS) due to the formation of an extra amount of hydration products such as CSHs and CASHs. In addition, the SEM image for AAS-0.5CrNPs specimen after being fired at 200°C and cooled slowly showed a dense structure compared to that of AAS after being fired at 200°C or after 28 days of normal curing (room temperature and 100% humidity).
11. The SEM images of specimens made from AAS-0.5CrNPs composite displayed the presence of large cracks in their microstructure, indicating complete deterioration of all binding phases.
Part C: Physicochemical properties and different applications of the AAS samples admixed with different doses of zirconium oxide (ZrO2) nanoparticles (ZrNPs).
Based on the results obtained in this part, the following conclusions could be derived:
1. All the prepared composites (AAS-0.25ZrNPs, AAS-0.5ZrNPs and AAS-1ZrNPs) showed high compressive strength values compared to that of control sample (AAS). This result is attributed to the essential role of Zirconium oxide nanoparticles in the progress of the hydration/activation process of slag.
2. AAS-1ZrNPs specimens showed the highest compressive strength values compared with all other tested composites.
3. AAS-1ZrNPs specimens showed the highest bulk density compared to the control sample, which confirmed the compressive strength results.
4. All composites prepared from AAS sample admixed with different ratios (0.25, 0.5 and 1%) of ZrNPs showed lower thermal resistance compared with that of neat AAS sample.
5. Specimens made from AAS-1ZrNPs composite exhibited the highest compressive strength values after being fired at different temperatures (200, 400, 600 and 900°C) and cooled with two different cooling regimes (gradual and rapid cooling) compared to other nanocomposites, but still lower than the control sample (AAS).
6. AAS samples incorporated with different doses of ZrNPs showed a high efficiency for shielding gamma-ray radiation from different sources (Co-60 of high intensity and Cs-137 of low intensity) compared to the control sample.
7. All the composites exhibited high linear attenuation coefficient values at low gamma ray intensity than that at high gamma ray intensity.
8. AAS-0.5ZrNPs specimens exhibited the highest linear attenuation coefficient values after exposure to different gamma-ray sources compared to other composites and to control (AAS).
9. The inclusion of different percentages of (0.25, 0.5 and 1%) ZrNPs within AAS matrix induced high inhibition efficiency against the growth of different types of microorganisms compared to the control sample. In addition, the AAS-1ZrNPs specimens showed the highest antimicrobial activity against used microorganisms, especially Staphylococcus aureus (ATCC 6538) with an inhibition zone of 70 mm compared to the other composites.
10. Differential thermogravimetric analysis curve (TGA/DTA) of the AAS-1ZrNPs specimen showed the highest weight losses percentages after 28 days of curing compared to all tested samples, these results attributed to the progress of the hydration/activation reaction resulting in the formation of a high amount of hydration products such as CSHs and CASHs.
11. Scanning electron microscope (SEM) image for AAS-1ZrNPs specimens after 28 days of curing revealed the presence of dense structure compared to the control sample (AAS) due to the formation of an extra amount of hydration products such as CSHs and CASHs.
12. The SEM image for the AAS-1ZrNPs sample after being fired at 200°C showed less compact structure compared to that of neat AAS after 200°C or at 28 days normal curing. This can be ascribed to the following reasons: (i) zirconia nanoparticles acted as an inhibitor or strong barrier for hydration/geopolymerization process at elevated temperatures; and (ii) ZrNPs may react with some cementitious phases to generate additional phases having lower thermal stability.
13. The SEM images for AAS-1ZrNPs specimens fired at 900°C exhibited large cracks along their microstructure, revealing the deterioration of all binding phases.
Part D: Physicochemical properties and different applications of the AAS samples admixed with different doses of copper oxide (CuO) nanoparticles (CuNPs).
Based on the results obtained in this part, the following conclusions could be derived:
1. AAS-0.25CuNPs, AAS-0.5CuNPs and AAS-1CuNPs specimens showed high compressive strength values compared to the control sample (AAS). This result is attributed to the basic role of copper oxide nanoparticles in the progress of the hydration/activation process of slag.
2. AAS-0.25CuNPs composite presented the highest compressive strength values compared with other composites and control (AAS).
3. AAS-0.25CuNPs specimens showed the highest bulk density compared to the control sample, these results agreed with and confirmed the compressive strength test results.
4. The incorporation of different doses (0.25, 0.5 and 1%) of CuNPs along the AAS matrix causes a notable decline in its thermal resistance performance.
5. AAS-0.25CuNPs composite exhibited the highest compressive strength values after being fired at different temperatures (200, 400, 600 and 900°C) and cooled with two different cooling regimes (gradual and rapid cooling) compared to other nanocomposites, but still lower than that of control (AAS).
6. AAS incorporated with different doses of CuNPs showed a high shielding efficiency against gamma-ray radiation of different sources (Co-60 of high intensity and Cs-137 of low intensity) compared to the control sample (AAS).
7. All the composites exhibited high linear attenuation coefficient values at low gamma ray intensity than that at high gamma ray intensity.
8. Specimens made from AAS-0.25CuNPs composite exhibited the highest linear attenuation coefficient values after exposure to different gamma-ray sources compared to all other tested composites.
9. The inclusion of different percentages (0.25, 0.5, and 1%) of CuNPs along the AAS matrix causes high inhibition efficiency against the growth of different types of microorganisms compared to the control sample. AAS-0.25CuNPs composite showed an exceptional inhibition rate against all the fungi and bacterium types, especially for Staphylococcus aureus (ATCC 6538) (62±1). compared to the other composites.
10. Differential thermogravimetric analysis curve (TGA/DTA) of the AAS-0.25CuNPs sample showed the highest weight losses percentages after 28 days of curing compared to all other samples and the control sample, which was attributed to the progress of the hydration/activation reaction resulting in the production of a high amount of hydration products such as CSHs and CASHs.
11. Scanning electron microscope (SEM) image for the AAS-0.25CuNPs specimens after 28 days of curing showed a denser structure compared to the control sample due to the formation of an extra amount of hydration products such as CSHs and CASHs.
12. The SEM image for the AAS-0.25CuNPs sample after being fired at 200°C and slowly cooled showed a less compact structure compared to the control sample (AAS) after fired at 200°C or after 28 days of curing at normal conditions. This result may be attributed to that copper oxide nanoparticles acted as an inhibitor or strong barrier for the hydration/geopolymerization process at elevated temperatures. Moreover, CuNPs may react with some cementitious phases to generate additional phases of lower thermal stability.
13. The SEM images for AAS-0.25CuNPs specimens after being fired at 900°C pointed the presence of large cracks in their microstructure, resulting from the deterioration of all binding phases.