Key Engineering Materials Vol. 509

Abstract: Montmorillonite (MMT), a typical layered silicate, has been widely used to prepare modified asphalt. This paper investigates the high temperature performance and low temperature property on layered silicate modified asphalt concrete. The control concrete is prepared by base asphalt. Meanwhile, three-point bending, conventional and SHRP rutting tests are used to compare the properties of the two types of asphalt concrete. The results of conventional and SHRP rutting tests show that the modified asphalt concrete exhibits a better high temperature performance than the control concrete. And the maximum bending strength of modified asphalt concrete is higher than that of control concrete at the same temperature. It can be concluded that both the high temperature performance and low temperature property of asphalt concrete has been improved efficiently by utilization of layered silicate modified asphalt.

Abstract: Abstract: The anti-aging asphalt modified by Supramolecular Ultra Violate(UV) Light Resistant material which is Layer double hydroxides (LDHs)was prepared in this paper, by using mechanical mixing, LDHs by various mass ratio were added into different typical asphalts. Taking the influence of the factors into account, including mechanical dispersing technologies, reaction conditions(temperature and time), content of the LDHs, the mutual consistent of LDHs among asphalt and storage stability was studied by segregation process and microstructure analysis (X-ray diffraction、Scanning Electron Microscope). Then after thin-film-oven-test (TFOT) and the artificial accelerated UV aging tests to simulate long-term UV aging, basic properties tests were conducted in this paper. The results showed that the UV anti-aging properties of the asphalt were greatly improved. Key words: LDHs; preparation manners; UV anti-aging

Abstract: This paper focuses on an optimized research about materials and size of electrode of self-monitoring asphalt concrete. It can be easily observed and analyzed the sensitivity of the test and resistivity fluctuations by studying the changes of output resistivity in different electrode embedded in the self-monitoring asphalt concrete. Based on the above method, we can select the proper electrode for the self-monitoring asphalt concrete. The results indicate that the output resistivity of self-monitoring asphalt concrete have much more fluctuation than which used stainless steel mesh as electrode material when choosing the iron mesh as electrode material. Meanwhile, the results demonstrate that the measured output resistivity of self-monitoring asphalt concrete is the most stable when the electrode size is 40~60% of cross-sectional area.

Abstract: With the widespread application of asphalt mixture, current demand from transportation managers for construction and maintenance of their pavement network consumes large numbers of aggregates. If agencies excessively favor to some certain kinds of excellent aggregates, the cost of construction could be considerably expensive. The major objective of this study is to determine the feasibility of utilizing dacite in asphalt mixtures. By means of Marshall, freeze-thaw, rutting and three-point bending tests, the performances of dacite and basalt asphalt mixture are compared. The results of the testing illustrate that dacite asphalt mixture is more susceptible to gradation and asphalt content than basalt asphalt mixture. Meanwhile it is showed that the performances of dacite asphalt mixture can be improved greatly with the involvement of additives including active mineral powder and cement. Furthermore, it is validated that dacite can be used as alternative aggregate in asphalt mixture.

Abstract: The color of allphatle sulfonated acetone-formaldehyde resin has been changed by a novel way of mixing with blue and green dye. The UV spectroscopy and colorimeter were used to characterize the color change. And the water reducing performance of the resin was investigated. The results indicated that the ratio of SAF water reducer to blue dye was 10:5, and that to green dye was 10:4, the color of the SAF water reducer can be efficiently changed. The fluidity of cement paste of SAF water reducer added the blue dye was improved, and the water-reducing rate was almost not influenced by addition of dyes.

Abstract: A simple and clean route to synthesize nano-scale mesoporous silver-silica composite aerogels was described here. The composite aerogels were obtained by adding a silver colloid to an about-to-gel silica sol prepared and then dried in supercritical anhydrous ethyl alcohol. The silver colloid and composite aerogels with silver content of 0wt%, 0.5wt%, 1wt% and 3.5wt% were characterized by UV-visible absorption spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectrometer (EDS), X-ray diffractometer (XRD) and N2 Brunauer-Emmett-Teller (BET). The results show that silver nanoparticles with size about 40nm are successfully impregnated into the spongy porous structure of silica. The surface area decreases from 845 to 443m2/g with the increase of silver content. And the nanoscopic surface and bulk properties of each component are retained in the solid composite.

Abstract: The non-isothermal crystallization kinetics of the MgO–Al2O3–SiO2 (MAS) glasses were analyzed with the Kissinger equation and the Augis-Bennett equation by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results showed that two crystal phases of spinel (MgAl2O4) and SiO2 were generated sequentially in the heat treatment process. When the spinel was the only crystal phase, the MAS glass-ceramic was transparent. For glass A (containing one type alkali metal Na2O), the corresponding activation energy was Ep1(A)=325.27kJ/mol, Ep2(A)=364.99kJ/mol; for glass B (containing Na2O and K2O) , the activation energy is Ep1(B)=233.79kJ/mol, Ep2(B)=273.85kJ /mol. The average crystallization index for spinel crystal phase was nA1=1.99, nB1=2.58, By adding K+, which suggested that the spinel crystal phase precipitation have the trend to change from two-dimensional pattern to bulk crystallization.

Abstract: In the present work, a series of glass samples in Ge-Se-Bi system are prepared. XRD analysis is made on samples for identifying the type of precipitated crystals from glass matrices. Effects of glass matrix composition on crystallization behaviors are discussed. Results show that Ge and Bi content of glasses in the Ge-Se-Bi system are closely related to the precipitation of pure Bi2Se3 thermoelectric crystal phase. The optimal glass-ceramic composition is presented.

Abstract: Abstract: Cordierite–alumina ceramics were prepared with the raw materials of cordierite and α-alumina powder, and TiO2，CuO and MgO were added as composite additives. The effect of MgO/ CuO ratios on the microstructure, thermal conductivity and thermal shock resistance of cordierite–alumina ceramics were researched by X-ray diffraction, scanning electron microscopy and laser flash analyzer; the bulk density and the porosity of cordierite – alumina ceramics were measured. The results show that with increasing of MgO/CuO ratios, the bulk density and thermal conductivity increase firstly and then decrease, and have a minimum with 0.4wt% MgO and 0.667 MgO/CuO; and the porosity of ceramics decreases firstly and then increases and has a maximum with 0.4wt% MgO and 0.667 MgO/CuO;There are little changes in the size of the grain of the ceramics, and a small amount of magnesium aluminate spinel precipitate; the thermal shock resistance performance of the ceramics is developed with the increasing of MgO/CuO ratios.

Abstract: Nanosized silver (Ag) was synthesized by reducing high concentration AgNO3 in N, N-dimethylformamide (DMF), in the presence of stabilizer polyvinyl pyrrolidone (PVP). PVP of two different molecular weights (MW=40000, 1300000) at the reaction temperature of 80°C and 100°C were tested for the effect on the formation of diverse silver nanoparticles. Our results indicated that the PVP with different molecular weights plays different role in the controlling of the Ag nanostructure owing to the PVP molecular selective adsorption on different crystal facets, thus affecting the growth rate of different facets of Ag nanoparticles. When all the other conditions kept the same and the temperature of 100°C, if PVP (Mw=40,000) was used, only a small amount of Ag decahedra were found. However, when the PVP with larger molecular weight such as PVP K88 (Mw=1300, 000), a large quantity of the triangular nanoprisms existed in the final solution in spite of the minority of quasi-sphere. The growth process and causation of different silver morphology with two distinct PVP have been briefly discussed.