Papers by Author: Jing Xu

Abstract: Using orthogonal experimental design, the influence of water-to-cement ratio, silica fume content, and fiber surface treatment on the electrical and mechanical properties of carbon fiber reinforced cement was studied. Moreover, the surface appearance of fibers with and without surface treatment was investigated by means of scanning electron microscopy. The results show that the effect of water-to-cement ratio on conductivity is the largest among all the three factors. Fiber surface treatment plays an important role in the mechanical properties of CFRC and the optimum way is HNO3 treatment. By adopting the method of efficiency coefficient, the best combination can be determined effectively.

Abstract: Investigation at micro- and nano-scale is beneficial for the fundamental study of cement-based material as an extremely complex composite. This paper presents a preliminary exploration on the unhydrated cement grain/ C-S-H gel interface using nano-scratch technique. By comprehensive analysis of the penetration depth, the coefficient of friction, and the elastic deformation ratio, the interfacial width of different w/c ratio and curing age were obtained, which shows a tendency to increase with the curing age in the range of 1-4 um, while has no relation to the w/c ratio.

Abstract: This paper presents a preliminary exploration in tribological property and dynamic elastic/plastic behavior of cement composite material at micro- and nano- scale. Pastes were prepared by pure cement clinker with water-to-cement ratio of 0.3 and 0.4. For comparison, a polymer-based clinker composite was also introduced. Nano-scratch test was carried out to study the scratch process. Different constituents were identified by penetration depth value. Based on this identification, the coefficient of friction and elastic deformation status were analyzed. Substrate effect was found when refers to the coefficient of friction of hard clinker particles embedded in soft matrix. An H/E ratio dependent elastic/plastic behavior was also revealed for cement composite. The results confirm the nano-scratch test as a promising method for cement composite investigation; however, some important attributes of this type of material, including the complexity of multi-phase structure and the viscous effect, need to be taken into account in experimental analysis and practical application.

Abstract: The galvanostatic pulse technique has been applied in detecting the efficiency of cathodic protection in reinforced concrete based on the investigation on the response of galvanostatic pulse to the corrosion state of steel and perturbation magnitude of signal. Two data analysis methods were introduced to determine the corrosion rate. It is shown that the selection of perturbation magnitude of signal to be applied depends strongly on the corrosion state of steel. Too small current makes it difficult to separate the potential signal from background noise, whereas higher current results in intensive polarization. Thus, neither of two is beneficial for the data processing. The corrosion rate values obtained from chronopotentiometry method are on the low side during cathodic protection monitored by higher perturbation signal and correction of data employing polarization conversion method is suggested.