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The effect of grinding aids has been explained mainly by two mechanisms. One is the alteration of the surface and mechanical properties of individual particles, such as a reduction of surface energy, and the other is the change in the arrangement of particles and their flow in suspension (Zheng; J. et al, 1997)(Oettel; W. and Husemann; K. 2004).
Surana, M.S. and Joshi, S.N., 1987 explained that the specific surface of a sample containing cement clinker, china clay and gypsum ground with 0.05% urea in the aqueous solution is 755 cm2/g higher than that of a sample without the grinding aid. The effect of methyl alcohol, ethyl alcohol, acetone, benzene, diethyl ether on the grinding of cement clinker in a ball mill was investigated by (Kim, B.K., 1975) and it was found that methyl and ethyl alcohol provided practical power saving and all of the aids decreased the compressive strength. Shakhbazyan, T.O. and Mikhaelyan, V.G., 1977 analyzed the effect of the wastes composed of activated carbon and zinc acetate on the specific surface area of the ground clinkers. Furthermore, 0.08–0.5% hydrophobic agents based on the weight of clinkers, such as calcium oleate, naphthenate, laurate, stearate or palmitate, or the free acids themselves are used at the clinker–gypsum grinding stage. But they may cause some retardation of setting (Bensted, J., 1992). Moreover, (Hekal, E.E. et al, 1999) (Hekal, E.E. et al, 2000) examined the mechanical and physicochemical properties of hardened Portland cement pastes containing hydrophobic admixtures. In addition, the waterproofing characteristics of polymer modified Portland cement mortars have been studied by (Saija, L.M., 1995). Besides these references, as known, whether the additives used to reduce the compressive strength according to the normal cement or not is very important. The main aim in this research is to investigate the effects of sunflower oil (SO) acid, oleic acid (OA), stearic acid (SA), myristic acid (MA) and lauric acid (LA) on the specific surface and the compressive strength of the normal cement.

I.4. The Object of Investigation:

The aim of this study is to examine the hydration characteristics of the different cementitious materials using various types of grinding aids in the presence and absence of limestone.

Twelve cementitious systems are used in this study:

1. Ordinary Portland cement (OPC) as a control mix.

2. (OPC) + Propylene glycol (PG) with different wt. % ratios (0.03, 0.04 and 0.05).

3. (OPC) + Commercial GA (CG) with various wt. % ratios (0.03, 0.04 and 0.05).

4. (OPC) +Ethylene glycol (EG) with different weight percent ratios (0.03, 0.04 and 0.05).

5. (OPC) + Triethanol amine (TEA) with different weight percent ratios (0.03, 0.04 and 0.05).

6. (OPC) + Propylene glycol and ethylene glycol (PEG) (1:1) with wt. % ratios of (0.04 and 0.05).

7. Portland limestone cement (PLC) with 5 % limestone as a control mix with the notation (OPC-L5).

8. Portland limestone cement (PLC) with 10% limestone as a control mix with the notation (OPC-L10).

9. OPC-L5 +PG with various wt. % ratios (0.03 and 0.04).

10. OPC-L10+ PG with various wt. % ratios (0.03 and 0.04).

11. OPC-L5+ CG with different wt. % ratios (0.03 and 0.04).

12. OPC-L10+ CG with different wt. % ratios of 0.03 and 0.04.

The aim of this work can be achieved via the following tests:

a. Determination of water of consistency and setting times
b. Determination of the compressive strength at various hydration ages (2, 7, 28 and 90 days).
c. Determination of the chemically combined water content at various hydration ages.
d. Determination of free lime contents at selected ages of hydration of a certain systems.
e. Investigation of the change in phase composition by using X-ray diffraction (XRD) analysis for some selected hardened cement mortars.
f. Investigation the thermal analysis using differential thermal analysis (DTA) for some selected hardened cement mortars.
g. Examination of the change in microstructure using a scanning electron microscope (SEM).

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