الفهرس 
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Abstract
SUMMARY AND CONCLUSION Blast-Furnace slags BFS are extremely interesting by-products of pig iron manufacture. Two types of slag are obtained; these are air-cooled slag (ACS is cooled by air and has less hydraulic activity). The granulated blast furnace slag (GBFS) is cooled rapidly by excess water and gives its latent hydraulic activity. Therefore, granulated slag (GBFS) is more active than air-cooled slag (ACS). This study aims to utilize Imported (GBFS) with Egyptian (ACS) for the preparation of pozzolanic (GBFS) or composite cement pastes from (GBFS + ACS).
The problem of producing pozzolanic cements has been of considerable scientific and technological interest because such the addition increases the chemical resistance to sulphate or chloride seawater attack, impermeability, lowering heat of hydration and thermal expansion. The use of pozzolanic cement is increasing world-wide because it needs less energy for production.
Blast-furnace slag is a by-product of iron manufacture and results from the fusion of limestone with minerals from the coke and the siliceous as well as aluminous residue remaining after the reduction and separation of iron from the ore. The GGBFS, which has a chemical role in removing sulphur from molten iron, rises to the surface and is tapped off from the blast furnace.
Fire is one of the major considerations in the design of buildings, it is extremely necessary to have a complete knowledge about the behavior of construction materials before using in the structural elements. Therefore, the effect of firing on cement pastes has investigated to show the positive effect of GBFS or ACS on firing.
This thesis deals with the utilization of two types of by-products such as GBFS (Imported) and air cooled slag (ACS) (Egyptian) in the preparation of pozzolanic cement. The hydration characteristics and the physico-chemical properties of the hardened cement pastes were studied up to 180 days of hydration. Also, the aggressive attack of seawater on some composite cement pastes was investigated up to one year of immersing in seawater. Some selected samples were investigated by XRD, IR and DTA/TGA techniques to show the aggressive attack of seawater on cement pastes. The effect of elevated temperature on the thermal behavior of cement pastes were studied on the hardened composite cement pastes using weight loss, compressive strength, bulk density, total porosity and free lime up to 800ºC for 2 hours socking time.
The materials used in this investigation were (OPC) from Suez Cement Company, air-cooled slag (ACS), provided from Iron Steel Company; Helwan, Egypt and the Imported GBFS is supplied by (Kokan Mining Co. LTD, Japan The GBFS and ACS were crushed by Jaw crusher and finely ground by using a laboratory steel ball mill having a capacity of five kilograms. the specific surface area was determined using Blaine air-permeability apparatus.
The dry constituents of OPC, GBFS slag and ACS of different mixes were mechanically mixed for one hour in a porcelain ball mill using five balls to attain complete homogeneity then kept in airtight containers until the time of cement paste preparation.
The hydration kinetics of pozzolanic or composite cement pastes were studied by the determination of the combined water as well as free lime contents. The water of consistency as well as setting times of each cement pastes was measured. The physico-mechanical properties such as bulk density, total porosity and compressive strength of hydrated cement pastes up to 180 days were determined.
Another set of all cement pastes was cured under tap water for 28 days (zero time) then immersed in seawater to investigate the resistance of aggressive attack of seawater at 1, 3, 6, 9 and 12 months respectively. The hardened cement pastes were tested for their resistance against attack of seawater. The relative seawater resistance of the hardened cement pastes is assessed by determining the changes in compressive strength, bulk density, total porosity, total chloride, total sulphate, combined water, and free lime contents for the immersed samples up to one year in Suez Gulf seawater.
To study the effect of fire, the pastes cured for 28 days (zero time) were kept 2 hours at 105, 250, 450, 600 and 800°C, then cooled to room temperature in the furnace. The cooled samples were covered with plastic film and kept into desiccators in order to avoid the influence of humidity and the carbonation of thermally treated pastes.
The following findings were obtained:
1. As the partial substitution of OPC by Imported GBFS increases the water of consistency of cement pastes decreases and the initial and final setting times shorten.
2. AS GBFS content in the pozzolanic cement increases the chemically – combined water decreases, due to lower hydraulic properties in comparison with OPC.
3. The bulk density and the free lime decreases as well as the total porosity increases with slag content.
4. 50 % GBFS give the higher compressive strength than other cement pastes at later ages.
5. The total sulphate and total chloride contents increase with the amount OPC at all curing times in seawater. The increase of total sulphate and chlorides is mainly due to the presence of portlandite from OPC hydration.
6. 60 % GBFS cement paste (A2) immersed in seawater the compressive strength of cement pastes increases up to 9 months and then decreases up to 1 year
7. As the GBFS content increases in the pozzolanic cement pastes show more resisting for fire up to 800°C.
8. The water of consistency of cement pasties slightly decreased with the substituted GBFS with ACS due to the low pozzolanic activity of ACS in comparison with GBFS.
9. The initial as well as final setting times are elongated with the amount of ACS. 10 – 20 wt % ACS that give small elongation.
10. As the GBFS decreases on the expense of ACS the accumulated hydration products and hence the combined water decreases, and the free lime increases.
11. The incorporation of ACS on expense of GBFS tends to increase the bulk density of heat treated cement pastes up to 800°C due to the higher specific gravity of ACS. On the other side, the substitution of GBFS with ACS decreases the compressive strength of heat treated cement pastes up to 800°C, due to the increase of C-S-H formed from OPC and pozzolanic reaction of GBFS with liberated CH.
12. Mix A4 (60 wt% OPC + 40 wt% GBFS) is more durable for firing up to 800°C due to the formation of calcium silicate aluminate ceramic materials which resist firing