Development of RC beam fortified with RPC without cracking at service state

混凝土结构中的裂缝会因钢筋锈蚀而导致耐久性恶化。虽然现行设计方法将裂缝宽度控制在允许的范围内，但有裂缝的混凝土结构比无裂缝的混凝土结构更容易发生劣化。本研究的目的是研制出在正常使用极限状态下不产生裂缝的钢筋混凝土构件。本研究注重超高强度的活性粉末复合材料(RPC)，特别是高抗拉强度对裂纹扩展的影响。RPC由水泥、硅粉、硅砂、特种减水剂、钢纤维等预拌粉末组成，对钢筋混凝土梁的部分张拉区进行加固。进行了梁的抗弯试验。RPC加固梁的裂缝发展弯矩随着RPC加固面积的增大而增大。普通钢筋混凝土梁在受弯矩作用时，由于钢筋锈蚀产生了允许裂缝宽度的裂缝，RPC加固梁不会出现适当的裂缝。RPC加固梁在使用状态范围内的受弯性能可用弹性理论进行分析。在估算裂缝发生时的弯矩时，必须考虑RPC自身收缩产生的约束应力。

Cracks in concrete structure cause deterioration of durability due to corrosion of reinforcement. Although crack width is controlled in less than the allowable value in the present design method, concrete structure with cracks deteriorate more easily than that without cracks. The objective of this study is to develop the reinforced concrete member that a crack doesn't occur in serviceability limit state. This study gave attention to a super high strength of Reactive Powder Composite (RPC), especially a high tensile strength on crack development. RPC consists of premixed powder in selected combination of cement, silica particles, siliceous sand, special water reducing agent, and steel fibers.A part of tension zone in reinforced concrete beam was fortified by RPC. Flexural load tests of beam were carried out. The crack development moment of the beams fortified by RPC increased with the increase of reinforcing area of RPC. When the bending moment that the cracks with permissible crack width for corrosion of reinforcement develop in the usual reinforced concrete beam acted, cracks didn't occur in the beams reinforced with RPC suitably. The flexural behaviours of the beam reinforced with RPC could be analysed by elastic theory in the range of service state. When the bending moment on the occurrence of the crack is estimated, the restraint stress due to autogeneous shrinkage of RPC must be taken into consideration.