Formación y características de hidratación temprana del C2.75B1.25A3enelsistemabinariodeC2.75B1.25A3 en el sistema binario de C2.75B1.25A3-C2S

C2.75B1.25A3$(2.75CaO•1.25BaO• 3Al2O3• SO3) is one of the important minerals and it govern-directly the early-strength of belite-barium calcium sulphoaluminate cement. In this paper a binary system C2.75B1.25A3$-C2S is selected to investigate the formation of C2.75B1.25A3$. In the range of 1100 °C–1200 °C, the earlier formed C2S hinders the formation of C2.75B1.25A3$. On the contrary, when the temperature is in the range of 1200 °C–1350 °C, the initially formed C2S could provide a surface for the nucleation of C2.75B1.25A3$and cut down the potential barrier (?Gk*) for the heterogeneous nucleation of C2.75B1.25A3$, which contributes to its formation. Moreover, at 1350 °C, the large amount of previously formed C2S benefits the extent of formation of C2.75B1.25A3$. The possible reason was that it could prevent sulfur evaporation. In early hydration age, AFm and AFt originating from C2.75B1.25A3$ hydration are found within 2 h and 12 h under 95% RH at 1 °C, respectively, whereas C2S is unhydrated at this moment.En el cemento de sulfoaluminato de calcio y bario, el C2.75B1.25A3$(2.75CaO•1.25BaO• 3Al2 O3• SO3) es una de las principales fases, y regula directamente la resistencia inicial del cemento. En este trabajo, se ha seleccionado el sistema binario C2.75B1.25A3$-C2S para investigar la formación de C2.75B1.25A3$. En el rango de 1100 °C-1200 °C, el C2S formado anteriormente impide la formación de C2.75B1.25A3$, mientras que cuando la temperatura está entre 1200 °C-1350 °C, el C2S proporcionaría una superficie de nucleación de C2.75B1.25A3$reduciendo la barrera de potencial (?Gk*) para la nucleación heterogénea de C2.75B1.25A3$, lo que contribuye a su formación. Además, a 1350 °C, la gran cantidad de C2S formado beneficia la formación de C2.75B1.25A3$, ya que podía prevenir la evaporación del azufre. En las primeras etapas de la hidratación (entre 2 y 12h y 95$, mientras que el C2S permanece sin hidratar

Effect of Aggregate Gradation with Fuller Distribution on Properties of Sulfoaluminate Cement Concrete

Aggregate, the main ingredient of concrete, has a great effect on mechanical property and durability of concrete. Sulfoaluminate cement has lots of special properties such as high early-age compressive strength, fast hydration and setting rate, and hydration with slight swelling. But effect of aggregate gradation with Fuller distribution on properties of sulfoaluminate cement concrete was seldom studied. Hence, in this paper, experimental investigations on mechanical property and durability of sulfoaluminate cement concrete with aggregate gradations according to Fuller distribution were presented. Fuller distribution of aggregates was beneficial to the close packing of aggregates, and the packing density was changed by adjusting the aggregate gradations. Compressive strength, water impermeability, and resistance capability to sulfate attack of SACC have the same trend of concrete with fine aggregates of Fuller distribution gradation \u3c concrete with fine aggregates of Fuller distribution gradation \u3c concrete with fine aggregates of Fuller distribution gradation. The relationship between packing density of aggregate and water penetration depth obeyed the second-order polynomial y = 0.002x2 – 6.8638x + 5862.3 and had a notable correlation R2 = 0.9799. The sulfoaluminate cement concrete with total aggregate gradation with Fuller distribution for h = 0.50 had the best resistance capability to sulfate attack. It was a second-order polynomial relationship between packing density of aggregates and water penetration depth of y = 0.002x2 – 6.8638x + 5862.3 with R2 = 0.9799, which indicated notable correlation. The fitting formula between packing density of aggregates and sulfate resistance coefficient of SACC was y = 0.0.0005x + 0.3704 with R2 = 0.9585

The Impact of Extended Heat Exposure on Rapid Sulphoaluminate Cement Concrete Up To 120°C

This study examined the stability of rapid sulphoaluminate cement concrete (R-SACC) when exposed to heat for extended periods of time. The physicochemical processes present in R-SACC as a function of temperature were determined through various tests. The general behavior of rapid sulphoaluminate cement (R-SAC) at a range of temperatures is summarized. The results show that observing color change could be a simple way to identify deterioration of R-SACC, along with the rebound hammer. The matrix formation of ettringite was broken and the mass of the hydrated product decreased with heat exposure; the major mineral composition of the paste consisted of CaSO4, CaCO3 and β-C2S; and the interface between aggregate and paste in the R-SACC become loosely structured with cracks. Between 50°C and 120°C, the rapid sulphoaluminate cement (R-SAC) paste first expanded and then shrank, and the shrinkage rate of R-SAC was much greater than that of R-SACC

Systematic Analysis of the Multiple Bioactivities of Green Tea through a Network Pharmacology Approach

During the past decades, a number of studies have demonstrated multiple beneficial health effects of green tea. Polyphenolics are the most biologically active components of green tea. Many targets can be targeted or affected by polyphenolics. In this study, we excavated all of the targets of green tea polyphenolics (GTPs) though literature mining and target calculation and analyzed the multiple pharmacology actions of green tea comprehensively through a network pharmacology approach. In the end, a total of 200 Homo sapiens targets were identified for fifteen GTPs. These targets were classified into six groups according to their related disease, which included cancer, diabetes, neurodegenerative disease, cardiovascular disease, muscular disease, and inflammation. Moreover, these targets mapped into 143 KEGG pathways, 26 of which were more enriched, as determined though pathway enrichment analysis and target-pathway network analysis. Among the identified pathways, 20 pathways were selected for analyzing the mechanisms of green tea in these diseases. Overall, this study systematically illustrated the mechanisms of the pleiotropic activity of green tea by analyzing the corresponding “drug-target-pathway-disease” interaction network

China's renewable energy policy: Commitments and challenges

The passing of the Renewable Energy Law (REL) in 2005 demonstrated China's commitment to renewable energy development. In the 3 years after the REL, China's renewable electricity capacity grew rapidly. From 2006 to 2008, China's wind capacity installation more than doubled every year for 3 years in a row. However, three facts prevent us from being optimistic about China's renewable electricity future. First, considered as a share of total capacity, renewable electricity capacity is decreasing instead of increasing. This is due simply to the rapid growth of fossil fuel capacity. Second, a significant amount of renewable generation capacity is wasted because it is not connected to the electricity grid. Finally, renewable electricity plants are running at a low level of efficiency. Based on an in-depth analysis of China's existing renewable energy policy, we suggest that these challenges should be dealt with by introducing a market-based mandatory renewable portfolio requirement coupled with strong regulatory monitoring of grid enterprises.Renewable energy Electricity China

EFFECT OF WELL-DISPERSED NANO-TiO₂ ON SULPHOALUMINATE CEMENT HYDRATION AND ITS APPLICATION IN PHOTO-DEGRADATION

Nano-TiO ₂ and sulphoaluminate cement have been received sustained attention due to their environment-friendly characteristic, respectively. Particular attention was paid to their materials composite. To better understand the effect of nano-TiO ₂ on sulphoaluminate cement hydration and its application in photo-degradation, the composite systems of cement paste (mortar) with well-dispersed nano-TiO ₂ were investigated by mechanical analysis, Rietveld/XRD, SEM, porosity analysis and photocatalytic test. The results reveal that nano-TiO ₂ can be well dispersed under ultrasonic treatment of 15min when the sodium hexametaphosphat is chosen as the dispersant. And the well-dispersed nano-TiO ₂, with the dosage of 0.2wt%, has the most significant effect on the mechanical improvement. Micro-analysis show that the mechanical promotion by nano-TiO ₂ is not attributed to the hydration degree increase but microstructure optimization. It is reflected in the decrease of porosity, mainly affecting the transitional pores (D=10~100nm), and spatial structures modification of cement paste where AFt was more likely to form as needle shape with shorter length-diameter ratio. The photocatalytic test demonstrates that the composite system (cement paste) has long-term effective photo-degradation property

The influence of different fine aggregate and cooling regimes on the engineering properties of sulphoaluminate cement mortar after heating

Previous experimental studies of sulphoaluminate cement after exposure to high temperatures have mainly concentrated on the resulting reduction of strength. Its behavior when heated continues to attract our attention because a systematic understanding of its heat-induced damage is needed to determine its reusability. The post-heating mechanical properties of sulphoaluminate cement mortar (SACM) made with three different types of fine aggregates after natural air cooling (NAC), water immersion cooling (WIC), and fire extinguisher cooling (FEC) are presented in this paper. Basalt and artificial sand have strong angularity, as indicated by their convexity and Wadell roundness values, which has an impact on improving their strength properties when heated. Convexity and Wadell roundness turn out to be independent, with convexity and circularity in good agreement. In addition, the loss of mechanical properties in river sand mortar was greater when either NAC or FEC was adopted than with WIC. The tests showed that independent of the type of sand, the SACM recovers its strength better when WIC or FEC is used in cooling rather than NAC

EFFECT OF MgO ON THE COMPOSITION AND PROPERTIES OF BELITE-BARIUM CALCIUM SULPHOALUMINATE CEMENT IN THE PRESENCE OF Na2O AND K2O

The purpose of this study is to explore the effect of MgO (1 - 9 wt. %) on the composition and properties of belite-barium calcium sulphoaluminate cement with additions of Na2O and K2O. The results show that 1 - 5 wt. % content of MgO can stabilize crystal types of M3-C3S, R-C3S and β-C2S. Moreover, MgO can promote the formation of C3S and C4AF, but has little effect on the formation of C2.75B1.25A3$ and C3A. The C3A/C4AF ratio is reduced by 22 % at 5 wt. % MgO, which indicates that appropriate MgO can decrease the liquid viscosity. In the presence of Na2O and K2O, the highest limit of incorporated amount of MgO is about 3 wt. %, which is higher than that in Portland cement clinker of 2 wt. %. Besides, MgO favors the formation of small C3S crystals in size of 4 - 20 μm. MgO enhances the hydration rate and mechanical property of cement at an optimal dosage (1 - 5 wt. %), beyond which an adverse effect could be resulted. At a MgO dosage of 5 wt. %, the compressive strengths of the cement at 1, 3, 7 and 28 days are 15.8, 39.3, 68.6 and 97.3 MPa, which increases by 116 %, 17 %, 10 % and 6 % respectively compared to the cement without MgO dopant. This study could lead to the effective use of magnesia-rich limestone in industrial production of belite-barium calcium sulphoaluminate cement

Constituent phases and mechanical properties of iron oxide-additioned phosphoaluminate cement

Iron oxide was added to phosphoaluminate clinker and its effects on cement constituents were determined using XRD, DSC, SEM-EDS and conduction calorimetry analysis. The variations in compressive strength were also studied. The results showed that in moderate amounts, iron oxide acts as a mineraliser during clinker sintering, furthering the conversion of CA_1-Y(P_Y) to LHss at a lower temperature than normally required for that reaction. The main constituents of iron oxide-rich phosphoaluminate clinker included LHss, CA1-Y(PY), CP_1-Z(A_Z) and ferrite. The EDS findings showed that the composition of the ferrite phase was nonuniform. The conclusion drawn was that by modifying the dose of Fe₂O₃) , the composition of phosphoaluminate cement can be controlled to produce clinker and cement compliant with different mechanical strength requirements. The conduction calorimetry findings were consistent with those results.<br><br>Este trabajo estudia, mediante DRX DSC, SEM-EDS y calorimetría de conducción, el efecto de la adición de óxido de hierro a un clinker de fosfoaluminato, así como las variaciones sufridas en su resistencia a compresión. Los resultados mostraron que en cantidades moderadas, el óxido de hierro actúa como mineralizador durante la sinterización del clinker, promoviendo la conversión de CA_1-Y(P_Y) a LHss a una temperatura más baja de la normalmente requerida. Los componentes principales del clínker de fosfoaluminato con óxido de hierrop son LHss, CA1-Y(PY), CP_1-Z(A_Z) y fase ferritica. Los resultados de EDS mostraron que la composición de esta fase ferrítica no era uniforme. DE este estudio se ha podido concluir que variando la dosificación del Fe₂O₃) , se puede controlar la composición del fosfoaluminato para producir clinker y cemento compatibles con diferentes requisitos de resistencia mecánica. Los resultados de calorimetría de conducción fueron consistentes con los resultados

Investigation of the Adaptability of Paper Sludge with Wood Fiber in Cement-Based Insulation Mortar

Paper sludge generated from the paper industry is classified as solid waste, comprising primarily wood fiber with excellent toughness and CaCO3 with low thermal conductivity. The purpose of this work was to investigate the adaptability of paper sludge with wood fiber into cement-based insulation mortar. The addition of paper sludge with wood fiber was found to be beneficial for optimizing the performance of cement-expanded polystyrene (EPS)/paper sludge (CEP) mortar. In detail, the addition of paper sludge with low fiber content in the range of 2.5% to 7.5% improved the toughness and softening coefficient of CEP mortar. In comparison, an increase of wood fiber content notably improved the properties of CEP mortar when its addition level reached 15%. Additionally, paper sludge with different fiber contents decreased the thermal conductivity of CEP mortar, ranging from 0.0897 to 0.0885 W/(m·K). In conclusion, paper sludge with wood fiber exhibited good adaptability in CEP mortar