Papers by Author: Bao Min Wang

Abstract: In this work, two type graphene were dispersed in aqueous solution via sonication, and graphene nanoplatelets (GP) and graphene oxide (GO) were characterized by means of ultraviolet visible spectroscopy (UV-vis), X-ray diffraction (XRD) and transmission electron microscopy (TEM). In addition, the effects of different graphene (GP and GO) on mechanical properties and microstructure of cement-based materials were investigated via filed emission scanning electron microscopy (FESEM). The results suggested that the incorporation of GP and GO both improved the flexural and compressive strength of cement, and the GP had a more prominent impact on the strengths of cement, compared with GO. The flexural and compressive strength of cement increased up to 23.5% and 7.5% with 0.05 wt% GP, respectively. FESEM analysis indicated that the microstructure of GP-cement paste was similar to that of control sample without graphene, whereas, a few flower-like crystals were generated in GO-cement paste. This work could provide a new understanding for further researches of graphene-cement composites.

Abstract: In recent years, more and more attention has been paid to the effect of stray current on the properties of cement-base materials in subway engineering. In the actual service process, reinforced cement-based systems suffer from various erosive conditions, the degradation mechanisms in reinforced cement-based systems due to the combined effects of stray current and environmental multi-factors have been a serious problem in civil engineering for many years. This paper reviews the research achievements on the properties of cement-based materials under the multi-factor coupling conditions such as stray current and soft water, chloride ion, sulfate, stress, freezing and thawing cycle and so on. Furthermore, the improvement of cement-based materials on stray current resistance is also generalized in it. Prospects of cement-based materials for durability under environment multi-factor coupling actions are also presented.

Abstract: In this paper, the dispersion of carbon nanotubes (CNTs) in cement matrix was analyzed by Three-dimensional Monte Carlo Simulation. A Hard core model was employed which was not allow the intersection among CNTs in a simulated three-dimensional representative volume element (3-D RVE). The position and the orientation of CNTs were assumed to follow the uniformly random distribution. The results showed that CNTs were dispersed randomly and it was helpful for the further simulation calculation about mechanical, conductivity and piezoresistivity properties.

Abstract: Basic performance test was performed on a newly-developed compound antifreeze and experiment was carried out to study the basic performance, mechanical property and durability of the concrete mixtures containing 0%, 4% and 5% antifreeze. The result shows the antifreeze may be used for the concrete construction at 20°C below zero and it has favorable performance for winter construction. When the amount to be added is 4% and 5%, the ratio of compressive strength of 28 days shall be 105% and 107% respectively; the ratio of compressive strength of 56 days shall be 114% and 112% respectively. In freeze-thaw cycle experiment, 50 times of freeze-thaw strength loss rate is 45.3% and 44.8% of the strength loss rate of the concrete without the antifreeze. The water-reducing ratio of the antifreeze, ratio of bleeding rate, air content, difference in setting time, strength ratio, ratio of shrinkage, permeated height ratio and other performance indexes all satisfy specification requirements.

Abstract: How to deal with used rubber has become a difficult problem worldwide. Adding powdered used tires in certain grain sizes to cement concrete can modify cement concrete, which is also a nuisance-free treatment and rational utilization thereof. In the early stage of research work, the author found that the rubber concrete mixed with fine used rubber powder whose grain diameters are 80, 100, 120 meshes showed a good anti-freeze durability. Based on these, the basic mechanical properties of rubber concrete within that grain size range are studied in this paper. The relations between axial compressive strength and cubic compressive strength, splitting tensile strength and cubic compressive strength are established to provide a design basis for engineering applications.