Materials Science Forum Vols. 743-744

Abstract: The influence of foreign ions doping on the property of belite - sulfoaluminate (BCSA) clinker with belite and calcium sulfo-aluminate as main minerals was investigated. The research on four foreign doping ions with P⁵⁺, B²⁺, Ba²⁺, and Zn²⁺ was carried out. The mineral components were characterized by SEM, X-ray powder diffraction and Infrared. Some foreign ions entering into the lattice of β-C₂S and during sintering at high temperature attained a high reactivity. The mechanism of the effect of these ions on stabilization and activation of minerals were clarified. Results revealed that P⁵⁺, Ba²⁺, and Zn²⁺ could stabilize and activate β-C₂S as well as enhance reactivity of, but no positive effect of ion B²⁺ was observed. The sequence of influence of different ions on C₂S is: Ba²⁺>P⁵⁺>Reference>Zn²⁺>B³⁺, and the sequence for was: P⁵⁺>Ba²⁺>Zn²⁺>Reference>B³⁺ . Compared to the 28-d compressive strength of reference one, P⁵⁺, Ba²⁺, and Zn²⁺ could enhance the strength by 15.6%, 8.9% and 26.5% respectively.

Abstract: In this paper, the property of common biomass-rice husk was compared with that of coal. The combustion characteristics of rice husk were investigated by Thermogravimetry (TG) method, and the barriers for biomass fuels utilization as an alternative fuel to manufacture artificial aggregates were also analyzed. The key techniques of using biomass as an alternative fuel in light-weight aggregate production, such as preprocessing of the biomass feedstock, proper design of combustion system for biomass fuel and control of sintering process were proposed. Properties of artificial aggregates sintered by biomass fuel were also studied according to GB/T 17421.2-2010 test method, and the test results showed that all the properties meet the requirement of national standard.

Abstract: LCI study is short for life cycle inventory study. In the situation of more strict regulation limit of 500 mg NOx /m³ a demonstration project to reduce NOx emissions with clinker production capacity of 2000 t/d in Beijing is supported by the 'Five-twelfth' National Science and Technology Support Program of China Science and Technology Department. A selective catalytic reduction denitration (SCR DeNOx) technology is expected to be applied in this project. LCA models the life cycle of cement manufacturing with SCR DeNOx technology applied as its SCR system. The life cycle is from the coal and raw materials transportation, through the coal and raw meal grinding, to the clinker incineration, and finally the flue gas including NOx to the SCR reactor. The functional unit is 1 ton clinker. Data for cement produced in LNB technology as bench mark is analyzed and the SCR scenarios are to show that the SCR reactor can be established because the additional environmental impact is small due to small consumptions of reducing agent and electricity. SCR technology enable the deNOx efficiency much higher with small environmental impact.

Abstract: The steel slag was broken into steel slag powders and sands. The performance of the radiation shield heavy concrete was studied in this work by mixing different content of steel slag sand and powder. The results showed that the water requirement of normal consistency and setting time increased with the increase of the content of the steel slag powder. The strength reduced in the early stage of the experiment. The strength increased firstly and decreased later. The optimal content of steel slag powder for strength was 20%. For the steel slag powder and sand, whether the concrete added one or two components, the concrete slump loss increased and strength reduced at 3 days. The steel slag powder and sand added into concrete improved the performance of the concrete effectively, solved the heavy aggregate subsidence and improved the concrete homogenous.

Abstract: MnO_x/TiO₂ catalysts are active and stable at low temperature, and it is appropriate for cement production to enforce NO_x emissions. In this study, the denitration process was promoted by the transformation of a variety of MnO_x forms in the SCR reaction. The efficiency and selectivity of catalysts depended on the form and dispersion degree of MnO_x. By changing the precursors, calcination temperatures, synthesis methods and calcination atmospheres, a series of MnO_x/TiO₂ catalysts were prepared. The contents and distributions of Mn²⁺, Mn³⁺ and Mn⁴⁺ in catalysts were tested through the titration method. The titration results showed that the content of Mn⁴⁺ was the highest during the precursor was Mn (NO₃)₂, while the content of Mn²⁺ in the catalysts calcinated in nitrogen atmosphere was the highest. The mechanisms of different MnO_x states in the catalytic process were discussed. It was found that a mixture of more MnO_x with low valence state and less MnO_x with high valence state were beneficial to the catalytic process.

Abstract: Microbe cement is a new generation cement due to the ever increasing awareness of environmental protection. Microbe cement is a new strengthening material based on microbiologically induced precipitation of calcium carbonate. This paper presents the results from laboratory research on the influence of magnesium additive concentration (1.0mol/L3.0mol/L5.0mol/L and 7.0 mol/L) on the mechanical properties of microbe cementitious materials. In addition, the micro-morphology and microstructure of microbe cementitious materials were analyzed by scanning electron microscopy (SEM). The experimental results indicate that when the magnesium additive concentration was 1.0 mol/L, the compressive strength of microbe cementitious materials can reach up to 6.2MPa at an age of 12 days. The microstructure of microbe cementitious materials depends on the content of mineral produced by microbially induced precipitation.

Abstract: The change of silica tetrahedron in cement-silica fume blends hydration is critical for blended cement application. ²⁹Si solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) investigations on the change of silica tetrahedron, which were Portland cement hydration, silica fume in simulated hydration and cement-silica fume blends hydration, were characterized and compared in this paper. The experimental results revealed that the amorphous silica tetrahedron structure in silica fume changed into Q¹ and Q² silica tetrahedrons, the same as silica-oxide structure of cohesive gel in the hydration of Portland cement. The coexistence of Q¹ and Q² silica tetrahedron in hydration product was beneficial to the strength increase of blend paste with silica fume. The amount of Q² silica tetrahedron in cement-silica fume blends was higher than that in Portland cement. The pozzolanic reaction of silica fume accelerated the course of the silica tetrahedron in blended paste turning into the stable state of Q² silica tetrahedron and existing principally in blended paste. That is reason that the physical properties of cement-silica fume blends are better than those of Portland cement.

Abstract: The effect of aluminium sulfate on cement properties was studied systematically and the mechanism was analyzed using XRD and SEM tests. Experimental results showed that the addition of aluminium sulfate will shorten the setting time of cement, increase the drying shrinkage and improve the early strength; however it will weaken the late strength of cement and reduce the fluidity. Micro-research showed that the addition of aluminium sulfate will change the morphology and location of aluminium sulfate distinctly.

Abstract: Coal tar pitch (CTP) mainly consists of polycyclic aromatic hydrocarbons (PAHs), some of which are carcinogenic. Among PAHs, benzo (a) pyrene (BAP) as one of the most prominently reported carcinogens which present in CTP causes the concerns of environmentalists. In this work, CTP was modified by styrene-butadiene rubber (SBR) through dynamic vulcanization. Ultraviolet-visible spectrophotometry (UV-VIS) was used to measure the content of BAP. After SBR modification through dynamic vulcanization, the BAP content have been reduced to 50%. With increasing the content of SBR,the content of BAP further reduced. The light component of the modified CTP decreased by the SBR modifier,verified by Headspace gas chromatography-mass spectrometry (GC-MS). Meanwhile, the SBR modifier has improved physical properties of the CTP, such as softening point, ductility, flowing property at high temperature. When the SBR content reached to 6 from 5.5, the softening point increased dramatically to 99 from 50.5. Thus, the modified CTP has various potential applications such as road pavement and carbon binder.

Abstract: Mineral wool is a type of important material for basic infrastructure development and national economy. It is widely used as insulation material in construction industries. Some high temperature industrial solid waste materials, such as blast furnace slag, cyclone slag and some metal slag, after composition adjusting and reheating, can be directly used to produce mineral wool. The recycle of residual heat in the hot solid wastes can decrease the cost of mineral wool and is beneficial for energy conservation, environmental protection and social sustainable development. The development and technical characteristics of mineral wool production with blast furnace slag, cyclone slag and some non-ferrous metal slag have been analyzed in this paper, and the energy conservation technique in managing high temperature solid waste has been also discussed.