الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Recently, advanced infrastructure is essential for economic growth and prosperity. Many of this infrastructure, especially those made of reinforced concrete, has suffered a severe deterioration since its construction due to environmental factors attacking and increasing live loads. One of the main problems faced by Civil engineers today is the maintenance and rehabilitation of these structures. The reactive powder concrete (RPC) is located under the High Performance Concrete (UHPC) category. This type does not include coarse aggregates and has excellent mechanical properties as well as durability characteristics due to homogeneity and dense microscopic structure. In addition, the increase in architectural spaces is a structural goal. This objective is achieved by increasing the joints and reducing the occasional columns that require the use of high strength concrete such as RPC, a relatively new cement material whose main components include a high proportion of Portland cement and very low water to cement ratio and included fine sand, silica fume and quartz powder. The coarse aggregate is completely replaced in RPC concrete with fine sand (0.6 mm) and quartz powder. It is characterized by high performance in mechanical properties, especially in compressive strength. This is of great interest to construction practitioners. . The main objective of this study is to produce different mixtures of RPC using the local market materials in Egypt. The experimental program has been divided into three phases. The first phase (Phase I) included of a number of different mixtures (10 RPC mixes). Different curing regimes: immersion in water at 20 ± 2 °C for 28 days or immersion in water at 60 °C for one week and then submerged in water at 20 ± 2 oC up to 28 days were used . The variables included: the water to cement ratios (0.21, 0.22, 0.23 and 0.25) the use of fly ash with silica fume (0 and 10%) and the use of 1% volume fractions of fibers (steel or polypropylene fibers). The specimens were tested in compression at the age of 7 days and 28 days, flexure at 28 days and splitting tensile test at age 28 days. The second phase (Phase II) was to study the performance of RPC as repair materials in compression, flexural and bond through (splitting tensile test and slant shear test at angle of 45ᵒ degrees with old concrete). Normal concrete specimens (NC) with (Fcu=25 MPa) were cast as a substrate concrete. After that, and at the age of 90 days RPC mixtures were applied to these specimens. The mixes of RPC in this stage were selected from the mixes of the (Phase I) due to its strength and appropriate flow. In the third phase (Phase III) of this study, six reinforced concrete beams were cast and tested, both RPC and NC or using the two types at the same time. Firstly, two beams of RPC and NC were cast with balanced reinforcement and with stirrups (flexural group). Secondly, two beams cast with a layer of RPC in tension or in compression zone of NC using balanced reinforcement and with stirrups. Finally, two beams were cast with RPC and NC concrete using over reinforcement and without stirrups (shear group). Experimental data for crack load, ultimate capacity, load deflections, load steel strain relationships, crack propagation and failure modes were presented for each beam. The test results of the (Phase I) showed that RPC can be produced using the materials available in the local market in Egypt. Compressive strength, flexural strength and splitting tensile strength tensile strength up to 140, 20.8, 18.6 MPa, respectively were achieved at 28 days. The optimum ratio of the water to cement was 0.21 for non-fiber mixtures and 0.22 for fiber blends. On the other hand, the use of fibers increased the compressive strength, flexural strength and splitting tensile strength by 14%, 104% and 91%, respectively, compared with mixes without fibers. The use of heat curing also increased the compressive strength, flexural strength and splitting tensile strength by 36.1%, 41.6% and 40.2%, respectively at the age of 28 days compared to specimens cured in water at 20 ± 2 oC. The test results of the (Phase II) showed the efficiency of the use of RPC as repair materials for NC. (Increases up to 132.6%, 100% and 106% for compression, flexural and bond (slant shear test) strengths, respectively for composed specimens in comparing with NC without a repair materials were achieved ). The test results of the (Phase III) showed that, firstly RPC beams exhibit a stiffer behavior than the NC beams. Also, the RPC reinforced beam specimen yielded about 4.6% higher than the NC. Secondly, using RPC in tension was found more effective than using RPC in compression. Hence, the cracking load actually represented at about 23% of ultimate flexural failure load for composed beam which have RPC in tension zone in compare with 17.5% for composed beam which have RPC in compression zone. Finally, the high compressive strength material (RPC) showed a significant increase in the ultimate capacity. The ultimate capacity of RPC beam specimen without stirrups showed about 71.1% higher than the NC specimen.