الفهرس 
Introduction, Literature Survey, and Aim of the WorkOnly 14 pages are availabe for public view
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Abstract
E
nvironmental pollution caused by various wastes has been a concern in the world and these pollutants are becoming hazardous to a human, animal, and environmental health as they accumulate for a long time. Get rid of these wastes by landfilling or dumping is harmful to the environment and has a high transport cost. Many efforts are therefore made using the solidification/stabilization (S/S) method inside a solid matrix to minimize the escape of heavy metals through leaching. Blast furnace slag, fly ash, and cement klin dust are the most popular solidification agents for inorganic wastes. Therefore, this study aims to investigate the immobilization of some heavy metal salts by three geopolymer pastes, alkali-activated ground granulated blast furnace slag (GGBFS), a mixture of GGBFS/FA, and a mixture of GGBFS/CKD pastes.
The heavy metals salts used in this study were lead nitrate and the chloride salt of copper and cadmium. The ratios used of these salt were 0.5 and 1%w.t of solid and the activator type is (NaOH/Na2SiO3) liquid by fixed ratio of (1:1)(5M NaOH).
In this study the effect of using heavy metal salts on the performance, physicomechanical, and hydration properties of different geopolymer pastes (alkali-activated slag, alkali activated GGBFS/FA, and alkali-activated GGBFS/CKD), as well as the degree of leachability, was examined via the following tests:
1. Determination of the compressive strength
2. Determination of chemically combined water contents
3. Determination of total porosity.
4. Determination of bulk density.
5. Leaching measurements.
6. X-ray diffraction analysis (XRD).
7. Infrared analysis.
8. Atomic absorption.
The main observation for obtained results can be summarized as the following:
1. The result of the chemically combined water contents increases for all -pastes with curing time up to 90 days for all alkali-activated mixtures due to the progress of formation of hydration products.
2. The value of compressive strength increase with curing time up to 90 days for alkali-activated pastes due to the formation of hydration products. The value of compressive strength of pastes with heavy metal salts is lower than those of pastes without heavy metal salts. As the ratio of heavy metals salts increases, the compressive strength decrease at all hydration ages.
3. The total porosity decreases with hydration time. This attributed to the formation of more hydration products, which precipitated in some available open pores leading to a decrease in the total porosity.
4. The bulk density of alkali-activated slag increase with curing time due to the continuous activation and formation of hydration products.
5. The combined water contents increase with curing time up to 90 days for all alkali-activated pastes due to the progress of the formation of hydration products as CSH and CASH.
6. The formed hydration phases were identified via XRD analysis.
7. All the investigated mixes containing heavy metal ions showed a high degree of immobilization.
8. While all alkali-activated slag, slag/FA, and slag/CKD observed Pb-concentration (mg/l) in leachate more than the limit of toxicity (0.001 mg/l) according to the Egyptian environmental law 1994; they observed low Pb-concentration (mg/l) in leached compared to the initial concentration 1% Pb+2 (10000 mg/l). This demonstrates the high efficiency of alkali-activated aluminosilicate materials in the immobilization of Pb+2, transforming hazardous slag to user and eco-friendly building materials.
9. The highest leached value of Pb+2 after 90 days is 0.217% of the original value in mix S4 (100 % slag+1%Pb+2).
10. The lowest value of Pb+2 after 90 days was 0.0193% of the original value in mix SC3(95 % slag+5%CKD+0.5%Pb+2).
11. mostly alkali-activated slag, slag/FA, and slag/CKD observed Copper-concentration (mg/l) in leachate below the limit of toxicity (1mg/l) according to the Egyptian environmental law 1994.
12. The highest leached value of Cu+2 after 90 days was 0.0449 % with mix SC2 (95 % slag+5% CKD+1%Cu+2) and the lowest value of Cu+2 showed for the mix S1(100% slag +0.5% Cu+2) was 0.0076%.
13. Mixes S5(100% slag +0.5% Cd+2) and SC5(85% slag +15%CKD+0.5% Cd+2) showed the highest degree of immobilization of Cd+2 ions after 90 days (" ~ "99.998).
Conclusion:
The main conclusions could be derived from this study can be summarized as follows:
1. The used heavy metal salts caused a retarding effect for the hydration of the investigated geopolymer mixes, and this retardation increase by increase heavy metal concentration.
2. According to XRD and FTIR analysis, the main hydration product formed are CSH and CASH.
3. All the investigated mixes showed a high degree of immobilization for all the examined heavy metals.
4. The best mixes for immobilization were SC3(95 % slag+5%CKD+0.5%Pb+2) is 99.980% for Pb+2 ions, S1 (100 %slag +0.5%CuCl2) is 99.992% for Cu+2 ions and S5(100% slag +0.5% Cd+2) & SC5(95% slag +5%CKD+0.5% Cd+2) is 99.998% for Cd+2 ions.