Belite-ye'elimite-ternesite (BYT) cement is a new type of cement with low energy consumption and carbon dioxide emissions. Notably, the sintering temperature of ye'elimite (C4A3$) is approximately 150 °C higher than that of ternesite (C5S2$) and belite (C2S). To facilitate the simultaneous presence of three minerals, the mineralizer (CuO) was used to reduce the formation temperature of C4A3$ in this work. Thermogravimetric (TG) was utilized to investigate the sintering temperature of minerals within the clinker. Furthermore, X-ray powder diffraction and scanning electron microscope were applied to analyze the phase composition and microstructure, respectively. The findings reveal that BYT cement clinker can be synthesized in one step at 1200 °C by adding 4% CuO. Ternesite (C5S2$) initiates hydration by 28 d, contributing to the stable development of medium-term strength. Optimal mechanical properties were observed with a ratio of C4A3$:C2S:C5S2$ at 40:50:10, achieving a 28 d strength of 43.7 MPa.
The resistivity of cement pastes in the early age was tested, according to the changes of resistivity and Ca(OH)2 content in the hardened pastes, cement hydration can be divided into four stages: the dissolution period, the induction period, the acceleration period and the deceleration period. The resistivity grows quickly when the induction period begins, differential scanning calorimeter and thermogravimetry analysis indicated that there were intermediate products at that time, which might be calcium aluminate hy- drates. The encapsulating effect of this quickly formed hydration products leads to the occurring of the induction period, which is consistent with the protective layer theory. The derivate curve of resistivity reaches a maximum in the acceleration period. X-ray diffraction analysis shows that this maximum was related to ettringite (AFt) transition to monosulfoaluminate (AFm). The hydration heat rate curve corresponds well with the derivate curve of resistivity. Resistivity shows a linear relationship with the Ca(OH)2 content after the induction period, the resistivity change reflects well the hydration degree.
: Great progress has been made recently in China concerning the research and development of belite based cements. This paper is a brief review of different system of belite cements. Some typical properties of these cements especially high belite Portland cement (HBC) are introduced. The study indicates that HBC, due to its low calcium mineral design, possesses not only lower clinkering temperature and less CO2, SO2 and NOx emission in its production, but also the characteristics of lower-heat evolution, higher late strength and excellent resistance to sulfate, etc. INTRODUCTION R & D OF BELITE BASED CEMENTS FUTURE DEVELOPMENT TREND REFERENCES
Quasi-brittle behaviors of cement-based material can be reinforced through diverse methods due to its unique multiscale features. Among them, reinforcing agents are the most direct and effective means, such as slag, metakaolin, and fly ash. These materials can improve the performance of cement stone to a certain extent, but their chemical composition is still mainly silica, which does not in essence change the defects of cement. Therefore, in this experiment, magnesium borate whisker (Mg2B2O5) was used as reinforcer of 90°C class G oil well cement and magnesium borate whisker reinforced cement-based material (MBWRC) was prepared. On the one hand, the performance of mechanical strength was controlled, and the resistance to compression, traction, and bending was included. Furthermore, static stress-strain behaviors analysis and toughness behaviors analysis (dynamic multicycle loading test) were further conducted. Second, mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM) were used to test the characteristics of pores and interfaces of cement-based materials. Through multiscale microstructure analysis, MBWRC was found to have excellent 90°C mechanical performances when compared to control sample’s, for which tensile strength increased to 235% of controlled sample’s, and flexural strength increased to 130%, plus a healthy developed compressive performance, and MBWRC showed much denser pore structure, in which harmless micropore increased from 13.3% to 14.40%, porosity decreased from 17.01% to 16.20%, and permeability decreased from 0.2533% to 0.0205%. Furthermore, MBWRC showed resistance capability to mechanical loading, which can be attributed to the formation of denser pore structure and more excellent mechanical performance.
Performances of belite-rich Portland cement, or HBC (high belite cement), and the resultant concrete are introduced by comparing with that of alite based PC (Portland cement) and concrete. The comparison study of cement properties indicates that HBC possesses the properties of less water demand for normal consistency, better compatibility with water reducer, higher later age strength after 28-day under standard curing temperature of 20 °C, unique strength gain under elevated curing temperatures of 38~70 °C, lower hydration heat evolution and temperature rise, lower drying shrinkage and excellent resistance to sulphate attack. These results have been demonstrated by the comparison performance evaluation of concretes prepared by HBC and PC in terms of workability, physical mechanical properties and durability when making high performance high strength concrete and massive concrete.
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