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Fiber Reinforced Concrete (FRC) can improve not only mechanical properties but also durability due to reduced crack width. Previous researches only enhance the advantages of fiber addition. From the view point of sustainability, the treatment of FRC after the service period of concrete structures should be one of the important issues in near future. This paper presents the ability of recycling of ordinary FRC having two kinds of fiber and different fiber content. It was clarified that fiber addition makes the size of crushed concrete smaller, and the size became smaller with increasing of the fiber content. In addition, the effect of fiber type (steel and PP) on the size of produced pieces was not significant. Eventually, crushing process, which is corresponding to the process removing mortar, can remove the fiber from the recycle aggregate, because the fiber is included within only mortar. [ABSTRACT FROM AUTHOR]

Abstract: Strengthening of Reinforced Concrete (RC) beams using strain hardening cementitious composites (SHCCs) layer cast to their soffit has recently been investigated. That work confirmed that strain localization occurs in the SHCC-strengthening layer, which severely limits the ductility of the strengthened beam. This paper reports the ductility enhancement achieved in tests on reinforced concrete beams that were strengthened with lightly steel-reinforced SHCC layer (0.3% and 0.6% steel reinforcement ratio). It has been found that the combination of the SHCC and a small amount of steel reinforcement helps develop higher strain in the SHCC strengthening layer at ultimate load and eliminates the observed early strain localization. The recorded averaged strain at ultimate load of SHCC-strengthening layer provided with 0.3% and 0.6% steel reinforcement was 2.10 and 3.76 times that of an unreinforced SHCC layer. Also, use of a 0.6% reinforcement ratio changed the mode of failure of the SHCC-strengthened beams from brittle to more ductile. Moreover, the SHCC-strengthening layer with 0.6% reinforcement ratio was able to develop uniformly distributed visible cracks, which were the only indication that failure was imminent. It needs to be emphasized that strengthening of RC structures using an unreinforced SHCC layer may lead to a brittle failure. [Copyright &y& Elsevier]

Abstract: There are a wide variety of short fiber reinforced cement composites. Among these materials are Strain Hardening Cementitious Composites (SHCC) that exhibit strain hardening and multiple cracking in tension. Quantitative material design methods considering the properties of matrix, fiber and their interface should be established. In addition, numerical models to simulate the fracture process including crack width and crack distribution for the material are needed. This paper introduces a numerical model for three-dimensional analysis of SHCC fracture, in which the salient features of the material meso-scale (i.e. matrix, fibers and their interface) are discretized. The fibers are randomly arranged within the specimen models. Load test simulations are conducted and compared with experimental results. It is seen that the proposed model can well simulate the tensile failure of Ultra High Performance-Strain Hardening Cementitious Composites (UHP-SHCC) including strain-hardening behavior and crack patterns. The effects of matrix strength, its probability distribution inside the specimen and fiber distribution on the tensile fracture are numerically investigated. Consideration of the probability distributions of material properties, such as matrix strength, appears to be essential for predicting the fracture process of SHCC. [Copyright &y& Elsevier]

Abstract: One of the novel mechanical properties of strain hardening cementitious composites (SHCC) is that they exhibit multiple fine cracks and strain hardening in tension. This promotes the use of SHCC as an effective repair material, because penetration of substances through the fine cracks is greatly reduced. Most research on SHCC has focused on its behavior and results obtained from uniaxial tensile tests. However, the crack distribution of the repair material (SHCC) layer is more concentrated adjacent to an existing crack in a substrate. So the design procedure considering the crack opening, which represents the potential for localized fracture, should be established for appropriate material selection. In this paper, the performance of SHCC as a repair material was assessed through three tests: uniaxial tensile tests; zero-span tensile tests; and flexural tests of RC beams repaired with SHCC. Comparisons between crack opening performances and the observed crack patterns of the three tests were conducted. The crack opening and crack pattern obtained from the zero-span tensile tests were similar to those of the repaired beam specimens. According to the zero-span tensile tests, the performance of cracking behavior of the repair material on an existing crack can be estimated. On the other hand, the deformation capacity of SHCC obtained from the uniaxial tensile tests cannot be directly applied to the design of surface repair application. [Copyright &y& Elsevier]

Bond quality is an important factor that affects the performance of repaired members. In patching repair, interfacial cracking and delamination due to the shrinkage of repair materials are often observed. In this study, flexural bond strength tests using jointed specimens were carried out, and the tension softening diagrams were determined by using experimental load-CMOD curves. These tension softening diagrams were adopted as the bond properties in numerical analyses to predict shrinkage and cracking behavior. For crack injection repair, bond strength tests based on the Japanese Industrial Standard (JIS) were carried out under conditions that are different from those normally encountered in the field (i.e. the tests involved smaller specimens, smoother surfaces, and finer grained materials). The bond properties of crack injection materials were evaluated using tension-softening diagrams. Size effect on flexural bond strength of repair materials was observed and clarified by numerical analysis with these tension softening diagrams. The analyses indicate size effect should be considered when evaluating the strength of larger structures in the field. [ABSTRACT FROM AUTHOR]

Abstract: Three-dimensional (3-D) effects in short deep beams without stirrups that failed in shear were investigated experimentally and analytically. Two deep beams with a shear span to depth ratio (a/d) of 0.5 and with different beam widths were tested. The effect of beam width on load-carrying capacity, failure mode, crack pattern and 3-D behavior was investigated, and shape effect due to beam width was clarified. In addition, the beams were analyzed by the 3-D rigid-body-spring model (RBSM). RBSM is a discrete form of modeling that presents realistic behavior from cracking to failure, and 3-D RBSM is applicable to simulate 3-D behavior as well as the confinement effect of concrete. Analytical results in terms of load–displacement curves and crack pattern are compared with the experimental results. Three-dimensional deformations, strut widths and cross-sectional stress distribution are investigated analytically and compared with the experimental results to determine 3-D behavior in detail. The 3-D effects in short deep beams are clarified. [Copyright &y& Elsevier]

Abstract: Cracking behavior due to rebar corrosion in concrete specimens having a single rebar is evaluated experimentally and analytically. In the experiments, in which corrosion was induced electronically, the propagation of cracks (including internal crack patterns and surface crack widths) was monitored. In addition, deformation of the specimen surface was measured using a laser displacement meter. In the analysis, a three-dimensional Rigid-Body-Spring Method (RBSM), combined with a three-phase material corrosion–expansion model, is proposed to simulate crack propagation due to rebar corrosion. The effects of the properties of corrosion products such as elastic modulus, penetration of corrosion products into cracks, and local corrosion after cracking of the concrete are investigated. Cracking behavior due to rebar corrosion is simulated reasonably well. The simulations using RBSM provide insight into the mechanisms of crack initiation and propagation due to rebar corrosion. [Copyright &y& Elsevier]

Micro cracks occurring in concrete around tensile rebar is well known latent damage phenomenon. These micro cracks develop, and can be detected after reaching the surface of the concrete. Detection of these cracks before they are fully formed is preferable, but observing the whole crack structure is difficult. Another problem is repairing micro cracks under the concrete surface. The autogenous ability of bond cracks along rebar was evaluated using the air permeability test. Air permeability coefficients were measured before and after tensile loading, and experimental air permeability coefficients became larger near cracks along rebar as a result of tensile loading. Recuring for 28 days after tensile loading made the air permeability coefficients smaller, but this restriction only occurred during water recuring. Observation of crack patterns helped the understanding of change in the air permeability coefficients. Several small cracks along rebar were observed after tensile loading, and most cracks along rebar were not found after water recuring. On the other hand, the crack pattern did not change after air recuring. These results indicate that bond cracks along rebar can be closed by autogenous healing, and cause the air permeability coefficients.