الفهرس 
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Abstract
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ABSTRACT
This thesis considers the mechanical properties and the durability characteristics of lightweight concrete .. The mechanical properties of the lightweight concrete studied herein were the cube compressive strength, splitting tensile strength, flexure strength, static and dynamic modulus of elasticity, length change and the ultrasonic pulse velocity. This research emphasizes the physical and chemical causes of deterioration on the durability of lightweight concrete. The course work emphasize pretreatment of lightweight aggregates (LECA) to ensure their stability over time in concrete under surface exposures. The chemical causes of deterioration investigated herein include; magnesium sulphate attack, sodium sulphate attack and sea water attack on concrete. After standard curing, the hardened concrete specimens were immersed in 5% magnesium sulphate, 5% sodium sulphate and natural sea water for different ages; after which the mechanical properties of the durability lightweight concrete (cube compressive strength, dynamic modulus of elasticity, length change and the ultrasonic pulse velocity) were studied. The physical causes of deterioration studied herein was repeated cycles of wetting and drying and the initial surface absorption test..
The fractional factorial method of experimentation has been adopted for the organization of the tests and the analysis of the results. The main advantages of this method are that: a) It measures interaction between factors, which cannot be achieved by classical methods of experimentation, b) It reduces the number of tests needed for the program without affecting the results as compared to the full factorial, c) It provides a statistical mathematical approach for the analysis at a later stage and d) It is possible to extrapolate results of tests omitted thus being able to optimize the various interacting factors influencing the materials performance.
To check the significance of each treatment factor the ANOVA method was performed on the results obtained from a program developed by the author using software MICROSOFT EXCEL. A fortran program developed at City University, London, by Dr. A. Abdou for evaluating the principal block and the complete factorial from a 1/9th fractional factorial experiment has been adopted by the author to a 1/311I fraction for his tests. Graphs presented in this thesis have been plotted using MICROSOFT EXCEL package.
The results of the study indicate that leca aggregate, produced in Egypt, is very reliable in producing structural lightweight concrete with compressive strength up to 300 kg/cm2• The concrete made with both ordinary Portland cement and sulphate resisting Portland cement acheived higher strength than that of concrete made with blast furnace slag cement after immersion in fresh water. While the SRPC concrete exhibited lower reduction in different mechanical properties such as cube compressive strength, UPV, weight loss, initial surface absorption and dynamic modulus of elasticity than that of the OPC concrete and BFSC concrete when it is exposed to sulphate attack, while OPC concrete exhibited higher reduction in sulphate resistance. On the other hand, the BFSC concrete acheived lower reduction in different mechanical properties when concrete exposed to sea water attack.