Materials Science Forum Vols. 743-744

Abstract: Artificial aggregates with high-performance were prepared by the methods including steel slag, furnace slag, fly ash and coal gangue, and the recycling concrete was prepared by artificial aggregates instead of natural aggregates. This kind of concrete abandoned was able to completely regenerate cement, which will make the reuse of concrete possible. The composition and characteristics of the artificial aggregates will produce a significant effect on the interfacial transition zone (ITZ) in recycling concrete. The morphological features and mineral composition of three artificial aggregates were analyzed by SEM and XRD, and the ITZ of three recycling concrete and one ordinary concrete was investigated by SEM and EDS. The results showed that compared with ordinary concrete, although the recycling concretes ITZ had a small amount of CH crystal, most of the space was filled with dense hydration products. The interface width was 40μm, which less than 50μm of ordinary concrete. Artificial aggregates with different ratio of raw materials had a great effect on recycling concretes ITZ. The ITZ of recycling concrete prepared with 30% steel slag, 50% furnace slag, 20% fly ash had the smallest Ca/Si and much more C-S-H. the structure of ITZ was much denser and the microstructure was relatively better.

Abstract: To establish a quantitative identification method of thaumasite, internal doping method was used to accelerate thaumasite form of sulfate attack (TSA). A cement-limestone powder paste doped 10% of magnesium sulfate was immersed in water at (5±2) °C, while the blank was in 10% magnesium sulfate solution (by weight). Paste corrosion products were analyzed by infrared spectrum (IR), thermal analysis, nuclear magnetic resonance (NMR), and X-ray diffraction (XRD)/Rietveld refinement methods. The results show that the thaumasite formation was successfully accelerated by internal doping method. A lot of thaumasite formed after 6-15 months low temperature sulfate attack with gray mud-like material. IR analysis is able to be used to analysis thaumasite qualitatively, and Rietveld refinement was suitable to quantitative analysis of thaumasite. A rapid quantitative identification method of thaumasite including visual inspection, IR spectrum and XRD/Rietveld refinement was also established which will improve the accuracy and rapidness of TSAs research.

Abstract: In recent years, superabsorbent polymers (SAPs) are considered as promising material for internal curing of cement-based materials, however, the relationship between SAPs structure and its performance are still unclear. In this paper, SAPs with different water absorption and size were selected to discuss their effect on autogenous deformation of cement paste and strength of mortars. Results indicated that SAPs with large-size and high-water absorption had positive effect on autogenous shrinkage reduction. The influence of SAPs on mortar mechanical properties revealed that SPAs seemed to have no negative effect on the strength of cement past. The increase of the strength might be from the decreased water/cement (w/c) ratio due to the water absorption by SAPs.

Abstract: The MnO_X-CeO₂/TiO₂ catalytic material for low temperature SCR of NO_X with NH₃ was prepared using aqueous solutions of three manganese salt as well as cerous nitrate and TiO₂(anatase) powder by impregnation method. The properties of the catalytic materials were investigated by TG-DSC, XRF, XRD, XPS, BET and SEM. And the low temperature catalytic activity of the catalytic materials was measured. The results showed that, when manganese nitrate and manganese chloride and manganese acetate were used as precursors, respectively, the primary phases of catalytic materials were MnOx/MnO₂, MnO₂/Mn₈O₁₀Cl₃ and Mn₃O₄/MnO₂, the surface Mn/Ti molar ratio were 0.68, 0.19 and 0.88, the surface area were 45.1m2/g, 25.1 m2/g and 48.6 m2/g ,respectively. The optimum NO_X conversion rate of catalytic material from manganese nitrate precursor and manganese chloride precursor and manganese acetate precursor were 97.9% at 483K, 86.6% at 513K, 97.2% at 423K, respectively. Consequently, the higher low-temperature activity of MnO_X-CeO₂/TiO₂ from manganese acetate precursor may be attributed to higher surface and higher surface concentration of activity component.

Abstract: The use of microbial cement to solidify tailings pile has been introduced and the tailings pre-product was made. In the laboratory, through the cementation performance test of small samples, the process parameters of the consolidation were discussed and some achievements in the use of tailings were developed.

Abstract: Using the industrial limestone, fly ash and pure chemical reagents as raw materials, the blast furnace slag was prepared in the simulation condition of the actual slag-making process. Using uniform design method, the influence of blast furnace slag composition factors such as quaternary alkalinity, ratio of CaO/MgO and ratio of SiO₂/Al₂O₃ on the glass content of blast furnace slag were studied in the present in investigation, the relationship between glass content and the various factors has been obtained through regression analysis, and the main influence factors and the optimum blast furnace slag compositions been found out. The results showed that, the impact of various factors on the glass content of granulated blast furnace slag was quaternary alkalinity > ratio of SiO₂/Al₂O₃ > ratio of CaO/MgO. According to the significance test of the regression equation and the verification experiment, it was concluded that the optimum compositions of granulated blast furnace slag were: the quaternary alkalinity was 0.85, the ratios of CaO/MgO and SiO₂/Al₂O₃ were 11.5 and 6.5 respectively, and in this condition, the glass content of granulated blast furnace slag reached to 98.47%.

Abstract: Finite element method (FEM) was used for analyzing the heat transfer problems of the PCMs and phase change gypsum board. The simulation results showed that the heat transfer rate of composite PCMs (phase change materials) is higher than the PCMs, the mixture of diatomite improved the heat transfer performance of PCMs. Compared with blank gypsum board,the cold side temperature of phase change gypsum board was decreased, and the temperature rise rate of the cold side was also delayed. The cold side temperature difference between gypsum board and phase change gypsum board was decreasing as the ongoing of heat transfer process.

Abstract: Utilizing the chemical reaction principles H₂O₂ was catalyzed by MnO₂, instead of being catalyzed by warm water. In the gypsum slurry, due to the chemical reaction of hydrogen peroxide a large number of bubbles were produced, and the material was self-foaming. The H₂O₂ foaming agent and the method of foaming affected the performance of the foaming gypsum, such as mechanical strength, apparent density, thermal conductivity, and the pore structure of foaming gypsum. The result showed that with adding H₂O₂, the apparent density and mechanical strength decreased; the different water/plaster weight ratio ranged from 0.65 to 0.75, affecting the foaming process. The thermal insulation property of FGD gypsum is related to the content of H₂O₂, the water/plaster weight ratio, and the pore structure of foaming gypsum.

Abstract: The deterioration behavior of cement-fly ash composite binder materials exposed to elevated temperature was studied in the present investigation. With the temperature continuous rising, the surface microstructure evolution of cement-fly ash composite materials was observed in a real-time mode. And the pore structure of the hardened paste undergoing high temperatures was investigated by mercury intrusion porosimetry (MIP) test. The results showed that thermal cracking of hardened paste developed continuously from the surface to the interior and hydration products decomposed gradually with the increase of temperature. Both the processes make the pores of the hardened pastes become coarser as well as the significant increase of the porosity, hence leading to worse deterioration of the microstructure and decline of the strength. The experimental results showed that the morphological effect and micro-aggregate effect of fly ash could improve the microstructure of cement-fly ash composite materials effectively, and the active effect of fly ash reduced the content of calcium hydroxide in the paste significantly. Both of them make contributions to the high temperature resistance of cement-fly ash composite materials.

Abstract: Approximately 416.9 million m³ of concrete were used in China in buildings, roads and other constructions in 2009. This makes concrete one of the most common building materials on the market. While consuming large amounts of energy, concrete industry has also cause large burden on the environment due to the environmental emissions by the production of cement and the transport of materials. Therefore, more detailed quantitative studies are necessary to finally acknowledge its effects of energy and environment. The objective of this paper is to identify and quantify the energy consumption, and environmental emissions during all life-cycle phases of concrete in China by LCA.