The shear characteristics of RC beam specimens strengthened with carbon fiber grid plates fixed at their edges by carbon fiber bundles were investigated in terms of the tensile strength of the carbon fiber bundles and the compressive strength of PCM. As a result, strengthening with the proposed method was found to be very effective for shear strengthening of existing RC members. Further, it was established that the carbon fiber bundles used for edge anchoring should have tensile strength at least 1.0 times the tensile strength of the tendons of the carbon fiber grid plate used for shear reinforcement. It was also established that PCM with compressive strength of 50 N/mm2 or more should be used. Finally, the formula proposed for the estimation of shear capacity of the strengthened beams was verified to be valid.
The out-of-plane bending performance of composite slabs consisting of RC and CLT joined with shear connectors (lag screws) was examined. Firstly, single shear testing was performed. The lag screws showed good slip performance. Secondly, bending testing was performed. The test revealed that the bending performance was higher with a narrower interval of shear connectors. A way of applying the conventional γ-method to determine the initial stiffness and yield load of composite slabs was then proposed. As a result, a good correlation was found between the calculation results and the experimental data.
The concrete waste generated when dismantling concrete structures is used as a roadbed material. However, the elution amount of hexavalent chromium derived from cement clinker may increase due to the progress of carbonation during storage. Therefore, in this study, we evaluated the effectiveness of the use of ground granulated blast furnace slag as one of the measures to suppress the elution of hexavalent chromium by elution tests and X-ray absorption fine structure measurements. As a result, we confirmed the reduction of hexavalent chromium eluted from the hardened cement by the reducing substance contained in the ground granulated blast furnace slag as the hydration reaction proceeded. Furthermore, the reducing effect of ground granulated blast furnace slag was maintained for a long period of time compared with other reducing substances. From the above results, we confirmed that ground granulated blast furnace slag is effective as a measure against the elution of hexavalent chromium.