الفهرس 
Introduction and Literature survey and Aim of the workOnly 14 pages are availabe for public view
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Abstract
The cement manufacture industry is thought to be one of the most polluting in the world. It is responsible for 5% of global warming emissions. Many attempts have been made to partially substitute ordinary Portland cement with some other inexpensive additives which may enhance the properties of cement pastes and reduce costs and energy as well. Examples of these additives are metakaolin (MK), ground clay bricks (GCB), ground granulated blast furnace slag (GGBFS), cement kiln dust (CKD).
The aim of this study is to examine the effect of pozzolanic materials like GBFS, MK, and GCB on the physio-chemical and mechanical properties of CKD-OPC and CKD-only pastes cured up to 180 days in water and 5% MgSO4 solution.
Four systems were used in this study:
1- 10% OPC with 60,50,40% CKD and 30,40,50% slag respectively.
2- 10% OPC with 60,50,40% CKD and 30,40,50% MK respectively.
3- 10% OPC with 60,50,40% CKD and 30,40,50% GCB respectively.
4- 40% CKD with 20% slag, 20% MK and 20% GCB.
To achieve full homogeneity, the cement and various additives are first mixed in a dry state. The pastes are made with the appropriate amount of water required for a standard consistency, then moulded into specimens using one-inch cubic moulds and cured for 24 hours in 100% relative humidity. The samples are removed from the moulds and cured in water for 3, 7, 28, 90, and 180 days. Some cubes are immersed (after 28 days curing in H2O) in 5% MgSO4 solution for different periods up to 180 days.
The compressive strength, total porosity, Bulk density, and chemically combined water content of various mixes immersed in water and in 5% MgSO4 solution are determined to investigate the hydration properties and resistance to sulphate attack. X-ray diffraction analysis is often used to define the phase composition of the formed hydrates in order to investigate the impact of different quantities of CKD on hardened blended cement past composition.
Conclusions
Several main points can be obtained from this study, are summarized in the following:
1. The compressive strength, combined water, density of all hardened cement pastes increase while total porosity decreases with increasing curing time. This is probably because of the progress of hydration and formation of additional CSH which is deposited in the open pores.
2. As the amount of CKD decreases and the contents of GGBFS, MK, and GCB increase, the values of compressive strength, chemically compound water and density increase except for HIII (10% OPC with 40% CKD and 50% GCB). This is mainly due to increasing the water of standard consistency.
3. The results of X-ray diffraction analysis for different mixes showed the presence of CSH, Quartz, CH, CaCO3, and β-C2S phases.
4. Since CKD is an enrichment source of hydroxide, 40% CKD significantly improves the geoepolymerization process by forming a well-refined and compressed matrix. But as the amount of CKD increases, mechanical properties deteriorate. This is mainly because of the higher alkalinity of CKD which has a negative impact on mechanical properties.
5. Compressive strength improves as the amount of slag increases. At all hydration ages, SIII mix (10% OPC with 40% CKD and 50% slag) has the highest compressive strength values. While HIII (10% OPC with 40% CKD and 50% GCB) gives the lowest values of compressive strength at all curing ages because of the lower pozzolanic activity of GCB.
Resistant to Magnesium sulphate attack:
1. The compressive strength, the combined water, total porosity and bulk density of all hardened cement pastes immersed (after 28 days curing in H2O) in 5% MgSO4 solution up to 180 days are studied. It is found that the compressive strength and bulk density increase up to 90 days then gradually decrease. While the total porosity decreases up to 90 days then increases due to the formation of expanding and softening ettringite hydrated products.
2. The chemically combined water contents increase with curing time up to 180 days because of the formation of ettringite and more CSH.
3. The delay in sulphate attack may be due to pozzolanic reactivity of GGBFS, MK and GCB which consume CH for the formation of more hydration products and the filling effect of MK and GCB. These hydration products fill a part of the available pore volume of the pastes retarding sulphate ions from penetrating the matrix.
4. Hardened cement paste containing 10% OPC with 40% CKD and 50% slag (SIII) shows the higher compressive strength values in sulphate medium.
After exploring the effect of some artificial pozzolana on hardened pastes composition and its resistance to sulphate attack, the data shows that using 10% OPC and 40,50,60% cement kiln dust (CKD) with various amounts of ground granulated of blast furnace slag (GBFS), metakaolin (MK) and ground clay brick (GCB) produce lower strength values than OPC. On the other hand, it delays sulphate attacks.
Finally, the prepared mixes can be used as a binding material in pavement blocks on the side of the road as it does not require high compressive strength.