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

混凝土结构中的裂缝由于钢筋的腐蚀而引起耐久性的恶化。虽然目前的设计方法将裂缝宽度控制在允许范围内，但有裂缝的混凝土结构比没有裂缝的混凝土结构更容易恶化。本研究的目的是研制在使用极限状态下不发生裂缝的钢筋混凝土构件。研究了活性粉末复合材料（RPC）的超高强度，特别是裂纹发展的高抗拉强度。RPC由水泥、二氧化硅颗粒、硅质砂、特种减水剂和钢纤维选定组合的预混粉组成。采用RPC对钢筋混凝土梁的部分受拉区进行加固。进行了梁的弯曲载荷试验。RPC加固梁的裂缝发展矩随着RPC加固面积的增大而增大。当普通钢筋混凝土梁中钢筋腐蚀允许裂缝宽度产生的弯矩作用时，RPC加固梁不发生裂缝。用弹性理论分析了RPC加固梁在使用状态范围内的抗弯性能。在估计裂缝发生时的弯矩时，必须考虑RPC均质收缩引起的约束应力。

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.