Carbon fiber cement paste piezoresistive sensors (CFCPS) are made of piezoresistivity of carbon fiber cement paste and mainly used for local monitoring of concrete structures. Two electrode fixing styles for measuring the resistance of CFCPS are compared and the conception of embedded gauze electrode is put forward. The characteristics, layout styles and configuration parameters of embedded gauze electrode and the methods for measuring the resistance of CFCPS are studied. The mould of sensors is designed and the data acquisition system based on voltage signal is developed. It is revealed that the four-pole layout is suitable for setting embedded gauze electrode and the direct-current four-pole method adapts to measure the resistance of CFCPS. The resistivity of CFCPS is independent of the area of voltage pole and the mesh size of gauze electrode. The space between current pole and voltage pole does not influence the resistivity of CFCPS when more than a critical value. The developed data acquisition system has many advantages such as simple circuit, good practicability, high precision and ability to realize real-time, on-line and multi-channel acquisition.

In order to develop one type of embedded piezoresistive cement-based stress/strain sensor (PCSS) to monitor the local compressive stress/strain of concrete structures, we explore the piezoresistivity of cement-based material with carbon fiber and carbon black under single compressive loading and repeated compressive loads at different loading amplitudes, and find it is reversible and stable within the elastic regime. This justifies the use of cement-based material with carbon fiber and carbon black in the manufacture of embedded PCSS. PCSS based on the piezoresistivity of cement-based material with carbon fiber and carbon black is tested with compressive stress/strainin the range 0 MPa (0 με) to 8MPa (476με) for performance evaluation. Results indicate that PCSS can be used to achieve a sensitivity of 1.35%MPa−1 (0. 0227% με−1, gage factor of 227), linearity of 4.17% (4.16%), repeatability of 4.05% (4.06%) and hysteresis of 3.61% (3.62%), and the relationship between its input (compressive stress/strain) and output (fractional change in electrical resistivity) is Δρ =−1.35σ (Δρ =−0.0227ε). These findings suggest that this newly developed sensor can be used as one of the alternatives to monitor the compressive stress/strain of concrete structures.

碳纤维与水泥石界面的粘接状况是影响碳纤维水泥石材料性能的关键因素之一，为此，通过测试碳纤维的表面浸润性以及碳纤维水泥石的力学性能，研究了经过NaClO氧化处理后，碳纤维表面性能以及碳纤维与水泥石界面粘结性能的变化。研究结果表明：碳纤维的氧化处理可以提高其表面对水的浸润性，改善碳纤维与水泥石的粘结界面，提高碳纤维水泥石的压敏特性。

研究了含有碳纤维、石墨、钢纤维的水泥基材料的导电性及其在压应力作用下电阻率的变化规律；探讨了掺有导电掺合料的水泥石电阻率的变化机理。研究表明，水泥基材料具备压敏效应的前提条件是其导电网络达到渗流区，而碳纤维由于长径比大、密度小，极小掺量即可使水泥石进入渗流区，产生压敏效应。

采用远场雷达散射截面法测试的功率反射率为表征吸波性能的指标，研究了素砂浆的吸波性能以及钢纤维长度、钢纤维掺量、复掺铁氧体、表面处理、温度和湿度等因素对钢纤维砂浆吸波性能的影响；同时根据所推导的隐身效能评价公式计算了钢纤维砂浆的隐身能力。研究表明：掺入钢纤维可以提高砂浆的低、高频吸波性能；合适的纤维长度和体积掺量是提高砂浆吸波性能的决定性因素；温、湿度升高，钢纤维砂浆的吸波性能下降；复掺的铁氧体分布在试件表层时，钢纤维砂浆的吸波性能下降，而分布在整个试件内时，可提高低频段的吸波性能；表面开浅槽可以在较宽的频段内提高吸波性能，表面开深槽可使低频吸波效果明显提高；吸波效果较好的钢纤维砂浆在2.6~4GHz的频段内，其雷达最大探测距离可降低到素砂浆的84%~89%。