الفهرس 
The specific surface area of the starting
MATERIALS AND METHODSOnly 14 pages are availabe for public view
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Abstract
SUMMARY AND CONCLUSION
Blast furnace slag is a by-product produced from the manufacture of pig iron. It is formed when the slagging agents (e.g., iron ore, coke ash and limestone) are added to the iron ore to remove impurities. In the process of reducing iron ore to iron, a molten slag formed as nonmetallic liquid (consisting primarily of silicates and aluminosilicates of calcium and other bases) that floats on the top of the molten iron. The molten slag is then separated from the liquid metal and cooled. If the molten slag is rapidly and sufficiently quenched by water, the ground product is known as ground granulated blast-furnace slag (GGBFS). The granulated slag is blended with Portland cement with up to 60 wt.,% slag to produce Portland slag cement. When the granulated slag reaches 70-75wt.,% it is called slag rich cement which can be used as durable cement in marine water. Slag rich cements containing 70wt.,% of granulated slag and 30 wt.,% of cement clinker possess excellent physico-mechanical properties and good durability against aggressive solutions. The high content of granulated slag decreases the amount of C3A as well as the liberated Ca(OH)2 during the hydration of portland cement, which are the main sources of attack.
The aim of this work is to prepare slag rich cement containing ground granulated slag from 45-75wt.,% of sulfate resisting cement. The hydration characteristics of blended cement pastes were studied from the determination of combined water, free lime contents and pH value of the hardened cement pastes as well as the bulk density and compressive strength up to 90 days.
The durability of slag-rich cements were also determined after immersing the cement pastes in Qaron’s lake water, Fayoum, Egypt up to one year. The rate of the aggressive attack was evaluated by the determination of combined water, free lime, pH value, total chloride and total sulfate contents in addition to the bulk density and compressive strength as a function of cement type and immersing time up to 12 months. Some selected cement pastes were investigated to show the hydration products by using DTA, IR and XRD techniques.
from the previous results, it can be concluded that:
1- The substitution of SRC by granulated slag tends to decrease the mixing water and elongates the initial and final setting times. This is mainly due to the low hydraulic properties of granulated slag in comparison with SRC.
2- The free lime contents of SRC pastes increase with curing time up to 90 days, due to the continuous hydration of β-C2S and C3S liberating free lime. On the other side, the free lime contents of slag rich cement pastes decrease with curing time from 3 up to 90 days as well as with the slag content. This is mainly attributed to the consumption of some of free lime with granulated slag in the pozzolanic reaction forming hydration products similar to be formed in the hydration of SRC.
3- The pH value of the hydrated cement pastes goes in the same direction of the free lime, i.e. increases with curing time for SRC pastes and decreases with curing time in the case of slag rich cement pastes.
4- The bulk density of hardened SRC as well as slag rich cement pastes increases with curing time, due to the continuous hydration and accumulation of hydration products in some of the open pores leading to increase of the bulk density. The bulk density of SRC pastes is higher than that of slag rich cement pastes. This is mainly due to that, the bulk density of the CSH of pozzolanic cement pastes is lower than that of SRC pastes. On the other side, as the slag content increases, the bulk density of cement pastes decreases. The pozzolanic cement pastes give hydration products with low density than that of portland cement pastes.
5- The substitution of 45-55wt.,% SRC with granulated slag gives a reasonable compressive strength nearly of that of SRC pastes up to 90 days of hydration.
6- The results of thermal, XRD and IR analysis are in a good agreement with those of the physico-chemical characteristics.
7- The combined water contents of SRC as well as slag rich cement pastes immersed up to one year in the aggressive water increase with immersing time, due to the continuous hydration. As the slag content increases, the chemically combined water content decreases, due to the lower hydraulic properties of granulated slag in comparison with SRC.
8- The free lime contents of SRC pastes immersed in Qaron’s lake water decrease with immersing time up to 3months and then increases up to one year. The decrease of free lime up to 3 months is due to the reaction of chloride and sulfate salts with the liberated portlandite, Ca(OH)2 forming gypsum (CaSO4.2H2O) and magnesium hydroxide Mg(OH)2. The produced magnesium hydroxide dissociates the CSH and Ca(OH)2 is liberated after 3 months of immersion. The immersed slag rich cement pastes show decrease of free lime from one month up to one year, due to the decrease of the liberated Ca(OH)2 and then Mg(OH)2 therefore, the slag cement pastes show good durability.
9- The pH values show the same trend of free lime because the Ca2+ is the main factor responsible for increasing the pH value in alkaline medium of cement pastes. 10- The bulk density of slag cement pastes increase with immersing time up to one year, due to the activation of soluble salts in the aggressive water forming more hydration products. In addition, the bulk density decreases with the slag content. In contrast, the bulk density of SRC pastes increases up to 3 months and then decreases up to one year. The increase of the bulk density up to 3months is due to the activation of SRC by SO42- and Cl- forming hydration products. However, from 3-12 months, the effect of SO42- and Cl- enhances the formation of chloroaluminate and sulfoaluminate hydrates leading to softening and expansion, and then the bulk density decreases.
11- The results of compressive strength of immersed cement mortars are in a good agreement with those of bulk density. In addition, the results of DTA, IR and XRD techniques are in a good agreement with each other and with the physico-chemical and mechanical properties of cement pastes and mortars.
It can be concluded that, the blended cements containing 45-55wt.,% granulated slag showed the higher hydration characteristics as well as the chemical durability on Qaron’s lake water up to one year of immersion.