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High temperature (HT) in-situ XRD method was adopted to investigate the calcium sulfoaluminate cement (CSA) or C4A3$ crystal architecture as well as its phases when passing through the temperature range of 20° to 70 °C. We examined the particle size analysis of the CSA ground powder when heated to different temperature (e.g., 35, 50, and 70 °C) in correlation with the HT X-ray diffraction (HT XRD) pattern as well with the compressive strength. The particle size of the lattice parameters increased during heating. The architecture transformation phase of the CSA took place at 50 °C. The transformation of the crystal cubic structure phase of the C4A3$ when passing from orthogonal to cubic space group was unstable with more heating (70 °C) and was adjustable. The C4A3$ compound's orthogonal and cubic crystal structures were clearly identified. The crystal structures were found to be responsible for the dehydration that occurred as the temperature rose and also for the decrease in compressive strength. The obtained final products of the C4A3$ were in cubic and orthogonal forms. The exothermic form of the C4A3$ was mostly observed at 20 °C and at 35 °C. The AFt and AFm crystal structure framework was constituted of AlO6 (in octahedral form) and AlO4 (in tetrahedral form).

A high belite sulfoaluminate cement clinker containing a magnesia-alumina spinel was prepared using industrial solid waste and high-magnesium limestone. The preparation procedure and the influence of the trace elements on the clinker were specifically investigated. This study reveals the mechanism of the clinker formation. The appropriate firing temperature of the clinker and holding time were determined to be 1300 °C and 60 min - 90 min, respectively. The presence of MgO and SO₃ displayed a positive effect on the clinker formation at high temperatures. In addition, the excessive MgO in the raw material was solidified to create the stable inertia mineral MgAl₂O₄, which eliminated the delaying expansion hazard of MgO.

This study dealt with the use of gold tailings, red mud, bauxite, desulfurised gypsum and high magnesium limestone as the raw materials in the production of a belite sulfoaluminate cement clinker containing MgAl₂O₄. The hydration and early mechanical properties of this cement were characterised by isothermal calorimetry, a mechanical test, X-ray diffraction and a thermal analysis. The results showed that the optimal calcination temperature to obtain a satisfactory clinker strength was 1350 °C and the corresponding 1, 3 and 7-day strengths were 27.7, 45.8 and 54.3 MPa, respectively. The initial and final setting times of the cements range between 20 and 31 minutes. The cements had the characteristics of rapid hardening and the main hydration products were AFt, AFm and AH₃. The total hydration heat release of this cement within the first 50 hours was only 158J/g, which could effectively avoid the generation of internal cracks in the cement and has the potential to be applied to large concrete projects. Furthermore, the MgAl₂O₄ mineral phase was inert in the belite sulfoaluminate cement and did not participate in the hydration reaction, which eliminates the disadvantage of MgO in the cement systems and potentially increases the use of high magnesium limestone in cement production.

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.

Calcium barium sulfoaluminate (abbr. C4-xBxA₃$), one of the special cementitious minerals originated from ye'elimite (abbr.C₄A₃$), has superior hydration and hardening performance. In this paper, a series of C4-xBxA₃$ with different Ba-doping concentrations (x=0, 0.5, 1, 1.5 and 2) were prepared, and the effect of the Ba-doping concentration on the formation was systematically investigated by the Rietveld/XRD quantitative phase analysis. The results show that BaSO₄ is the essential intermediate phase for the formation of the Ba-doped ye'elimite. The solid-state reaction process of C4-xBxA₃$ is separately expressed as two main forms, corresponding to the cases in which the Ba-doping concentration (x) is larger than and less than "1", respectively. The Jander diffusion model shows the optimal fitting for C4-xBxA₃$ and it clearly proves that the C4-xBxA₃$ formation becomes increasingly difficult as the Ba-doping concentration increases. The correlation between the apparent activation energy (Ea) and the Ba-doping concentration is positively well related, which can be expressed as 'Ea) =71.9x+304' (kJ/mol).

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.