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CRC ( Compact Reinforced Composite) is the designation for a special type of fiber reinforced concrete with high strength (150-400 Mpa) and closely spaced reinforcing bars. The dense matrix-with water/powder ratios of typically 0.16-provide a good bond to fibers and reinforcing bars, and the large content of steel fibers provide the ductility necessary for utilizing reinforcement effectively. The steel fiber content is typically 2-6% by volume and the content of reinforcing steel is 2-10% by volume. The improved durability of the matrix- due to a high micro silica content-makes it possible to use a concrete cover to the reinforcement of only 10mm in aggressive environments, improving the effectiveness of the reinforcement. The CRC concept was developed in 1986 and aimed specifically for use in structures such as beams, columns and joints, but most of the applications so far have been in the security industry, for corrosion protection and in heavily loaded floors. However, in the last few years CRC has also been applied in structures. One of these applications, production of 40,000 drain covers for a tunnel as a replacement for cast-iron covers, is described as an example of a project where the properties o high performance fiber reinforced concrete were utilized.

The structural behavior of steel fiber reinforce concrete beams in shear is studied. A comprehensive experimental program has been set up and several series of reinforced concrete beams with steel fibers have been tested. The test variables include the volume contents of steel fibers and stirrups. The fiber contents varies from 0% to 2% by volume. It is seen form these tests that the cracking and ultimate shear strengths increase as fiber content increase. The present study indicates that fiber reinforcement can reduce the amount of shear stirrups may accomplish strength requirements s well as ductility requirements. A theoretical approach is proposed to predict the shear strength of reinforced concrete beams containing steel fibers and good correlations obtained with test data. The present study allows more efficient structural application of steel fibers for shear reinforcement in reinforced concrete structures.

The mechanical behavior of a few plain and fiber-reinforced high performance concretes (fact=80-130 Mpa) is studied here by means of direct tensile tests and three-point bending tests, and a special "identification" Procedure is adopted in order to cleanse the stress-strain and stress-displacement curves of any undesired structural effect. The overall behavior of two P/C beams typifying the sub-elements of a hollow-core slab is examined, with and without fibers, to sturdy crack formation and propagation ( by optical interferometry) and structural ductility.

The use of steel fibers as shear reinforcement in reinforced concrete beams is very promising. In this paper, an optimized high strength concrete with steel fibers (100 kg/m3) is used in rectangular beams (2.3 times .25 times .125 m), reinforced with longitudinal bars. This solution is compared with classical reinforced concrete. Five specimens are tested in four-point bending. The 28-day mean compressive strength of concrete is 90 Mpa measured on cylinders. The global behavior of the equal for all tested beams but the cracking is equal for all tested beams but the crack opening is smaller with steel fibers. No problems were encountered concerning ductility.

Considerable progress has recently been achieved in strength and ductility of concretes. The use of superplasticizers and large amounts of silica fume led to densified cementitious matrices and improved adherence to the fiber reinforcement. These two properties are obtained with Compact Reinforced Composite (CRC) developed at Aalborg Portland and closely studied during a 3-year EC. The investigations reported in this paper cover the application of ultrahigh strength-fiber reinforced concrete to enhance performance of beams, columns and beam to column connections. Mechanical tests were performed on full scale structural elements. Beams of 13 m in length, columns of 2.9 m in compression with and without eccentricity of the load, and beam to column connections were tested. In all cases, concrete strengths of more than 150 Mpa were achieved. Due to CRC's high compacity and its extreme resistance to the penetration of aggressive elements, the CRC cover to the reinforcement was typically reduced from 30 mm to at least 12 mm. It has been shown that a reduction in concrete cover to the reinforcement is compatible with the requirements of structural applications. The tests carried out have shown the possibility of using ultra-high strength concrete for large-scale structural concrete elements and opens new fields of applications. This contributes to saving raw materials, weight and volume and to improving ductility and durability.