| Popis: |
Blast-Furnace slags BFS are extremely interesting by-products of pig iron manufacture. Two types of slag are obtained; these are air-cooled slag (which is cooled by air and has less hydraulic activity). The granulated blast furnace slag (GBFS) (which 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 utilization of Egyptian air cooled slag and comparison between its main characteristics with Imported granulated slag which has a higher hydraulic activity than ACS due to its amorphous (glassy structure) to produce some types of blended cements having reasonable phyisco-mechanical properties. 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 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. 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. 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. Some selected samples were investigated by XRD, IR and DTA/TGA techniques 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 slag is finely ground using a laboratory small steel ball mill having a capacity of five kilogram; the specific surface area was determined using Blaine air-permeability apparatus. 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 dry constituents of OPC, GBFS slag and ACS 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 physico-mechanical properties such as bulk density, total porosity and compressive strength of hydrated cement pastes up to 180 days were measured. Also, the water of consistency as well as setting times of each cement pastes was measured. Another set of all cement pastes was cured under tap water for 28 days (zero time) then cured under seawater to investigate the resistance of aggressive media such as 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 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 a desiccators in order to avoid the influence of humidity and the carbonization of thermally treated pastes. |
