الفهرس 
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Abstract
Hydraulic cements are those of interest in making of concrete which have the property of setting and hardening under water, due to chemical reaction. A hydraulic cement when mixed with enough water to form a plastic paste, the mixture starts to set, loses its plasticity and becomes hard. The paste continues to harden and develops strength. Most important engineering properties of concrete such as strength, volume stability and permeability to water are mainly determined by the properties of the hardened cement paste.
Natural prompt cement is produced by firing a unique clayey limestone at moderate temperatures. This special cement forms constituents such as active dicalcium silicates, alumina rich calcium aluminates and calcium sulphoaluminates, the mineralogical composition properties are quick-setting, rapid hardening and resistance to acid water. The quick-setting properties of prompt cement elongate by citric acid retarder or by Portland cement. The organic retarders contain hydroxyl and carboxylic groups such as citric acid.
Pozzolanic cements are usually blends of cement with other finely ground materials. The most common blending materials such as WCS, GCB (homra) and silica fume (SF). These cements need less energy for production and reduce the environmental problems of the green house effect.
Composite cement is hydraulic composed of Portland cement and two or more inorganic materials that take part in the hydration reaction and there by making a substantial contribution to the hydration product.
Granulated slag (WCS), homra (GCB) and silica fume (SF) are waste by
-products produced in large quantities. These mineral admixtures may be ground together with the cement or mixed. Concretes using composite cement can have properties that are desirable for particular purposes, such as slower and decreased total heat evolution in massive structures, improved durability or with microsilica, strengths above the normal range.
This study is devided into seven sections as follow:
I. The first Section deals with the hydration characteristic of hardened prompt cement with citric acid retarder at (0.0, 0.5, 0.75, 1.00 and 1.25%). The hydration was conducted at 1, 3, 7, 28 and 90 days.
II. The second section is the hydration characteristics of substituted OPC by 10, 20 and 30% prompt cement.
III. The third section includes the hydration characteristic of substituted prompt cement by 10, 20, and 30 %WCS.
IV. The fourth section deals with the hydration characteristic of substituted prompt cement by 10, 20 and 30% homra (GCB).
V. The fifth section aims to the hydration characteristic of substituted prompt cement by 5 and 10% silica fume.
VI. The sixth section contains the hydration characteristic of two kinds of composite cements, each kind substituted by 10, 30 and 50% prompt cement.
The previous sections from the first to the sixth, deal with the assessment of the hydration characteristic by the determination of combined water, free lime as well as bulk density, total porosity and compressive strength cement pastes and XRD for some selected samples..
VII. The seventh section deals with evaluation the fire resistance of different cement pastes; prompt, prompt-SF, and composite- prompt
cement at 105, 250, 450 and 600C for soaking time 2h at each temperature then kept to cool in the furnace. The fire resistance was measured from the bulk density, total porosity and compressive strength.
The materials used in this investigation were ground granulated slag which provided by Iron Steel Company, (Helwan, Egypt), ordinary Portland cement (OPC) from Suez Cement Company, (Suez, Egypt), Homra (GCB) from Misr Brick Company, (Helwan, Egypt), prompt cement from prompt cement Vicat Company, (Paris, France) and condensed silica fume (SF) from Ferro silicon Alloys Company, (Edfo, Aswan, Egypt).
Chemical and mineralogical characterization of prompt cement, ordinary Portland cement (OPC), homra (GCB) condensed silica fume (SF) were determined using chemical analysis, and XRD.
The mixing of the pastes was placed on a smooth, nonabsorbent surface. The amounts of mixing water as water of consistency poured into the crater by the aid of a trowel, mixing for about 2 minutes, and the paste placed in ½ inch stainless steel cubic moulds and cured for 24 hours in humidity chamber then demoulded and cured under tap water up to the time of testing.
The following findings were concluded:
1- Hydration of prompt cement with and without citric acid retarder was reported up to 90 days. The initial and final setting times of prompt cement pastes were elongated with citric acid retarder according to the dosage. Also, the hydration products decrease with the retarder dose. The chemically combined water contents, free lime, bulk density, total porosity and compressive strength go in the same direction and the optimum dose of citric retarder was 0.5wt%.
2- The influence of replacement OPC by 10, 20 and 30% prompt cement was studied. The initial and final setting times were elongated with prompt percent 10, 20 % but shortened with 30 %. Also, the compressive strength of cement pastes decreases with prompt % and the optimum prompt % is 10 and 20%. These results are confirmed with the combined water, free lime, bulk density, total porosity, compressive strength and XRD.
3- The influence of replacement prompt by 10, 20 and 30% granulated slag was undertaken. The initial and final setting times are slightly elongated due to lowering prompt% and high water demand for high surface area of slag. Also, the hydration products decrease with the increasing of substituted slag percent, and the optimum results are with 10% slag. These are confirmed with the combined water, free lime, bulk density, total porosity and compressive strength and XRD.
4- The effect of homra replaced in prompt by 10, 20 and 30% was investigated. The initial and final setting times are slightly effected. Also, the hydration products gradually decrease with homra percent, and the optimum results were with 10% homra.
5- The effect of 5 and 10% SF by on the initial and final setting times of prompt cement are slightly affected due to high surface area of SF and filling pozzolanic effect. The hydration products increase with SF content due to the role of SF as nucleating agent for conversion Ca(OH)2 to CSH and the optimum results were with 10% SF
6- The influence of prompt cement by 10, 30 and 50% on composite cement M (60% OPC- 40% GCB) on the initial and final setting times were shortened with prompt%. The optimum results were obtained in mix 10% prompt with 90% composite M.
7- The influence of prompt cement by 10, 30 and 50% on composite cement N (60% OPC- 20% GCB- 20% WCS) on the initial and final setting times were shortened with prompt %. The optimum results were obtained when mix 10% prompt with 90% composite N.
8- The effect of fire on the properties of cement pastes at 250, 450 and 600C at rate of heating 10C/min and soaking time for 2 h at each temperature and kept to cool in the furnace was determined. The effect of fire on the mechanical properties as well as physical properties of cement pastes was carried out by the determination of the bulk density, total porosity and compressive strength as well as visual inspection of cement pastes at definite temperature.
a. The effect of firing temperature on pozzolanic (prompt- silica fume) cement on the firing resistance was investigated. 10% SF indicates that silica fume consumes Portlandite forming CSH fills some of open pores, and diminishs the surface cracks.
b. The effect of firing temperature on [OPC- Homra- Prompt] composite cement was determined. The optimum results of firing resistance are of Ma mix which indicate that homra consumes the Ca(OH)2 to form CSH fills some of open pores, and diminish the surface cracks.
c. The effect of firing temperature on [OPC- homra- slag- prompt] composite cement was investigated. The optimum results of firing resistance are of Na mix, these indicate that homra and slag consume Ca(OH)2 to form CSH fills some of open pores and diminishs the surface cracks.