In September 2000, the American Concrete Institute sponsored the ACI Fourth International Conference in Seoul, Korea. Sixty-two papers are included in this publication. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP193

This paper presents the concrete structure repairing method, using concrete with expanded polystyrene granules (EPS). Reinforced concrete slabs are cast with depression of the top surface up to 70 mm. For the top surface leveling, with minimum selfweight load addition, a new flooring system is developed: over the sound isolation layer, EPS concrete leveling layer, 60-130 mm thick, (p = 450-500 kg/m3, Bk = 1-2 MPa) is cast. As a top finishing surface, high performance concrete layer, 15 mm thick (Pk = 60 MPa) is cast. Flooring system satisfied all the requirements, with total weight of 55-90 kg/m2.

This paper presents the results of an experimental study on shear Synopsis: strength enhancement of reinforced concrete (RC) beams with adhesive bonded flexible carbon fiber sheets. A total of eight medium-sized RC beams are tested under four-point bending. Different sheet configurations and fiber alignments are used to clarify their effects on ultimate shear strength of tested beams. It is found that the externally adhesive bonded carbon fiber sheets are effective for enhancing the shear strength of RC beams. Further, it is observed that the sheets with fibers aligned parallel to beam axis are nearly as effective as that of sheets with fibers aligned perpendicular to beam axis. Moreover, the shear strengt increases with the number of sheet layers and the depth of sheets across the beam section. Maximum shear strength is obtained for the beam U-wrapped by sheets over full depth having fibers perpendicular to beam axis. An 119% increase in ultimate shear strength is achieved for this beam with single layer of fiber sheet.

Confinement of concrete by transverse steels (tubes or spirals) is effective in improving ductility of high-strength concrete (HSC). While the circular transverse tubes or spirals can provide much stronger confinement to the compressed concrete than the rectilinear transverse steels (tubes or ties), and circular reinforced concrete column is widely used in building and civil structures, studies and information on the flexural behavior of circularly confined concrete columns are scarce. As a result, there is not yet a reliable ultimate capacity design method directly applicable to circular concrete columns in current design codes. In this paper, a simple ultimate capacity design method is proposed for the circularly confined HSC columns. This simple method utilizes an equivalent rectangular stress block for the compressed concrete in circular column section. Since expressions of the parameters definingu the stress block and the ultimate strain were developed based on an confinement model proposed by the authors, the proposed design method enables engineers to compute directly ultimate capacities of a circular column, and to evaluate the confinement effect of circular transverse steels on the ultimate capacities. The predicted ultimate moment and curvature agreed well with the experimental data of HSC columns confined by circular steel tube and circular concrete-filled steel tubular (CFT) columns available.

An important factor for the success of repair works in concrete structures is to realize sufficient bonding between the repair material and the substrate. Nowadays there are many types of repair material available in the market with improved strength, adhesion, waterproofing and durability properties. There is a need to study the interfacial properties of these repair materials especially in-situ because these properties depend very much on method of placing, curing and environment condition etc. The authors developed a new testing method called the torque test to measure bonding shear strength by twisting concrete cylinder cores. Since concrete is weaker in tension than in shear, slant tension failure often occurred and pure torsional failure could not be achieved. The data from this type of failure are considered the minimum bonding shear strength. To prevent this type of failure, the top concrete cylinder is enclosed in steel pipe. The experimental parameters are the adhesives between two concrete such as epoxy resin, polymer modified cement mortar and cement mortar. The influence of surface roughness of concrete substrate on bonding strength is also investigated. A relationship between bonding shear strength and bonding tensile strength is obtained.