الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Now the world is going to alleviate the weight created with access to the required resistance, and thus the production of lightweight concrete may be studied on a large scale, but there are some problems that we face as structures for this type of concrete, such as low-stress. This research deals with solving problems are: Improve the strength of lightweight concrete using local materials to become a construction concrete. After a group of structural lightweight concrete mixes, we face another problem which is exposure to harsh environmental conditions such as permeability, reduce the absorption, and resistance to sulfate attack. Large amounts of experimental work have been carried out worldwide to investigate the Lightweight concrete. A series of mixtures were conducted to select the best mixtures in terms of low unit weight and higher compressive strength, the material used in this study are natural sand, crushed stone (Dolomite), CEM I 42.5 N, silica fume, limestone powder, leca (fine and coarse) and chemical admixtures (super plasticizer and foaming agent admixtures). Tests to determine the properties of the materials were carried out according to the Egyptian Standard Specification (E.S.S) or the ASTM. In the experimental work, the fresh concrete properties such as (slump test), the hardened concrete properties such as (compressive strength, tensile strength, flexural strength and modulus of elasticity) and the durability of concrete such as (water absorption, permeability and sulfate attack) were carried out. A total of forty one concrete mixtures were performed with different cement contents of 315, 350, 420 and 450 kg/m3 at w/c ratio between 0.25 : 0.50, the amount of water was adjusted according to cement content, the silica fume ratio was ranged between 8 : 20% as addition and replacement of cement content, limestone powder ratios were 0.39 and 0.78 of cement content, the super plasticizer dosage varied from 0.6% to 3.0% of cement content to achieve the required level of workability defined by a slump value of 10 ± 2 cm. The percentage of replacement of normal weight fine and coarse aggregates by lightweight fine and coarse aggregates was 50%. In some lightweight concrete mixes was used foaming agent admixture by percentage between 2 : 6% of cement content. The obtained results indicate that the LECA as lightweight aggregate and foaming agent admixture can successfully be used for making structural lightweight concrete and non-structural lightweight concrete. An investigation to improve the compressive strength of lightweight concrete and the flexural behavior of lightweight reinforced concrete beams by strengthening with one, two and three layers of glass fiber laminates. A series of forty four lightweight reinforced concrete (LWRC) beams of 700 mm length and a rectangular cross section of 100x100 mm were cast, strengthened and then tested under three-points bending test to study the effectiveness of using externally applied Glass Fiber Reinforced Polymer (GFRP) composites as a method of increasing the flexural strength of under-reinforced LWRC beams. The beams were divided into four groups; the first one consist of four beams represent the control group, the second group consist of twelve beams strengthened with GFRP before loading, the third group consist of twelve beams loaded to 80% of load levels, unloaded, and then repaired with GFRP, before loading up to failure, and the fourth group consist of sixteen beams with and without GFRP and submerged in 10% sulfate sodium for six months, before loading up to failure. The variables considered for this study were four concrete mixes and the number of GFRP layers with and without exposure to sulfate attack. The behavior of the tested beams was analyzed in terms of ultimate carrying load, ultimate deflection, mode of failure load and toughness. Despite of the experimental results illustrated that, the cylinders and beams strengthened with GFRP laminates exhibited better performance. Also the results show that, the use of GFRP as an external reinforcement to strengthen or repair concrete structural members (pre-loaded) is more effective.