الفهرس 
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Abstract
In the present investigation, two types of Portland cement pastes were prepared(a)neat cement pastes made ”by using various water/ cement ratios ranging from 0.22 to 0.50 , and (b) polymer - impregnated pastes as composites made from the above mentioned neat cement testes by impregnation of the D - dried pastes, after hardening for various ages, in a monomer, and then polymerization of the monomer within the pore system of the specimens using various doses of γ-ray. the monomers used are methyl methacrylate, styrena and. Btyrene / acrylonitrile mixture.
Physioo chemical studieo were carried out on the neat cement pastes, hardened for various ages, with regard to bulk density, compressive strength, degree of hydration, total water contents, and total porosity; in case of the polymer- impregnated specimens only bulk density and compressive strength were investigated.
the results Obtained in -the present study indicate some important characteristics, and these may be summarized as follows:
neat Cement Pastes*
A.l. the bulk density increases with increasing curing age of the paste, and with decreasing the initial Water/ cement ratio, a result which is namely attributed to the accumulation of cement hydrates within the pore system of the hardened paste with age of hydration.
A. 2. Compressive strength increases with increasing age of hydration and with decreasing the initial water/cement ratio of the paste. this result is associated with the decrease in the total porosity and the increase in the total contents of the binding centers in the hardened paste (degree of hydration) with increasing age of hydration,
A.3. Combined water contents, Wn show a marked [increase of the Wn value with increasing age of hydra¬tion and with increasing the initial space available for the accumulation of hydration products (initial water/ cement ratio).
A.4. She total porosity of the hardened paste decreases Markedly with increasing age of curing and with decreasing the initial water/ cement ratio.
A. 5. the total water content, wt, increases with increasing time of hydration. due to the increase in the amount of water gained by the paste during the hydration, process under water.
A.6. Compressive strength results could be correlated with the degree of hydration, the total porosity and the Power’s gel - space ratio, and meaningfull relations could be derived.
B* polymer_~ Impregnated cement Pastes as composite . Materials t
B.1 She bulk density of the impregnated specimen for all monomers studied, inereases with increasing the total irradiation dose for all hydration ages and at all initial water/ cement ratios.
the increase in the bulk density is greater for the pastes made with higher water/ cement ratios (higher initial porosity.).How ever, the bulk density of the polymer - impregnated specimen decreases with age of hydration, a result which is a associated with the retard of diffusion of the monemer into the specimen with the accumu¬lation of the cement hydrates within the pores of the paste with increasing age of hydration.
B.2.Compressive strength results of the polymer impregnated pastes ware found to depend primarily on the type of vinyl monomer, the impregnation with styrene, acrylonitrile mixture gave the greatest improvement of [the strength, then methyl methacrylate and styrene, a result which is related to the hardness of the polymer or copolymer. also the extent of strength improvement sis higher at the early ages of hydration and diminished at the later stages of hydration. In addition, the strength increases with increasing the irradiation dose clue to the’ increase in the amount of polymer in the pores of the paste.
B.3. the strength of the polymer impregnated paste was also related to the degree of hydration, total porosity and the Power”” gel - space ratio. 2he various factors; affecting the strength, of the composite material were also discussed.