In order to meet the need of current codes used for buildings and highway bridges in China to control crack breadth of concrete structure surface, according to electromechanical sensibility of carbon fiber smart layer, tests were applied to determine surface crack breadth of test beam with precast crack. Monotonic three-point bending method was presented for loading through controlling deflection of test beam. The experimental results indicate that polymer based carbon fiber smart layer can sense the change of surface crack breadth which increases with the increase of loading, and electrical resistance of carbon fiber smart layer linearly increases with the increase of surface crack breadth which varies from 0 to 1.0 mm. Polymer based carbon fiber smart layers have different sensitivities for crack breadth. When surface crack breadth varies from 0 to 0.5 mm the electrical resistance is 2-4 Ω, which is greatly linear with crack breadth. It can be utilized to detect concrete surface harmless crack width from 0 to 0.3 mm by current codes used in China through which dispersion of electrical resistance of polymer based carbon fiber smart layer within this period is little.%针对国内现行建筑和路桥规范对混凝土结构表面裂缝宽度的控制要求,根据碳纤维智能层的力电传感特性,采用单调三点弯拉静力加载制度,以试件梁的挠度进行加载控制,对带有预制裂缝的混凝土梁试件表面裂缝宽度变化进行检测试验.研究结果表明:树脂基碳纤维智能层传感器可感知混凝土粱裂缝宽度的变化；随着荷载的增大,裂缝宽度增大,碳纤维智能层的电阻也发生相应变化,而在混凝土裂缝宽度0～1.0 mm时,碳纤维智能层的电阻随裂缝宽度的增大呈线性增大趋势；树脂基碳纤维智能层对裂缝宽度变化的敏感性存在差异,但是,混凝土表面裂缝宽度在0～0.5 mm之间变化时,碳纤维智能层的电阻在2～4Ω之间变化,其离散性不大,且线性关系好,可满足国内现行规范允许混凝土表面无害裂缝宽度0～0.3 mm的检测要求.
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