Formation Of C3S Research Articles

Effect of alkalis on the mineral formation and properties of alite-sulfoaluminate cement

This work studied the effects of alkalis on the mineral formation of alite-sulfoaluminate cement clinker and the properties of its cement, using limestone, fly ash, clay and gypsum as raw materials. The results indicated that minor amount of alkalis can improve the burnability of raw mixtures and accelerate the absorption of free lime. Excess amounts of sodium oxide (Na2O) or potassium oxide (K2O) (about 1·2%) were found to be adverse to the formation of C4A3S¯. The alkali distributes mostly in the interstitial phase, much less in belite crystal and then only traces in alite crystal. When the amount of alkali is about 1·2%, Na2O benefits the formation of C3S and can increase the early strength of cement. K2O, on the other hand, decreases the amount of formation of C3S and lowers the various age strengths of the cement. Adding alkalis prolongs the cement setting time.

Effect of Barium on Formation and Metastable Structure of Tricalcium Silicate

The effect of barium on the formation, structure and phase transition of tricalcium silicate (C3S) has been studied by X-ray powder diffraction combined with Rietveld method, Differential scanning calorimetry and Fourier transform infrared spectroscopy. The results showed that the low contents of barium was favorable the formation of C3S with up to 1.5% BaO. Higher amounts of BaO inhibited the C3S crystallization and lead to preferential formation of dicalcium silicate solid solution. Three triclinic forms T1, T2 and T3 of C3S were stabilized. The lattice parameters changed linearly to the barium content, however the discontinuity appeared at the phase transformation boundary, which follows the Vegards law. The crystallographic structure of T1 and T2 was similar to that of T3. The SiO44- tetrahedra were distorted in T1 and T2, while that was approximately regular tetrahedron in T3. The phase transitions of C3S were influenced by the incorporation of barium. It was believed that the stabilization of high temperature polymorphs of C3S was related to the lattice distortion caused by ionic substitution.

Influence of MgO on Sintering and Property of Belite-Barium Calcium Sulphoaluminate Cement

The effect of MgO on performance of belite-barium calcium sulphoaluminate cement (B-CBAS) was investigated through orthogonal tests. The results show that the formation of C3S can be improved at low temperatures by mixing MgO. SO3 decreasing the viscosity of fused mass in sintering process was beneficial to solid solution of MgO in B-CBAS clinker. The solid solubility of MgO in B-CBAS was higher than that of Portland cement, which indicated that high-magnesium limestone can be used in B-CBAS. Even MgO content reached 5.14%, the soundness of B-CBAS was still in safe, whose compressive strength at 3d and 28d curing age were 49.1MPa and 81.9MPa. This indicated that this kind of cement has good mechanical properties.

Solid Solution Mechanism of CO2O3 During C3S Formation

Polymorphism of tricalcium silicate were prepared by a calcination method with Ca(OH)2 and SiO2 as crude materials and Co2O3 as doping agent. The solid solution mechanism of Co2O3 during C3S formation were studied by means of chemical analysis, XRD and phase diagram analysis. The results show: according to phase analyse of CaO-CoO and CoO-SiO2, Co2O3 accelerated solid reaction of CaO-SiO2. When Co2O3 additive was less than 1.5% in mass, the content of f-CaO increased with the increase of Co2O3, and the formation rate of C3S was accelerated by Co2O3; when Co2O3 addition exceeded 1.5%, the content of f-CaO decreased with the increase of Co2O3. By the least square method and defined f-CaO, the molecular formula that Co2O3 solidified in C3S could be deduced: (Ca3-0.86x Co0.86x) (Si10.14xCo0.14x) O5 (x=0.0209).

Preparation and in vitro bioactivity of zinc incorporating tricalium silicate

Zinc incorporating tricalcium silicate (Zn-C3S) at various concentrations (0.80–8.00wt% Zn) were prepared and investigated as compared with the pure C3S. The incorporation of Zn promotes the formation of C3S phase during the calcining process, and inhibits the phase transformation and decomposition of C3S during the quenching process. The excessive incorporation of Zn (≥4.80wt%) results in the disappearance of the main heat libration during the hydration of Zn-C3S. The incorporation of Zn decreases the pH value of SBF solution after soaking, and increases the ionic dissolution concentrations. The deposition of apatite on Zn-C3S paste surface is inhibited during the first 12hours of soaking. However, the apatite layer could deposit on the surface of Zn-C3S paste after soaking for 3days. Our results indicate that the incorporation of Zn significantly improves the formation and stable of C3S, and alters the bioactive behaviors and ion releases to the SBF solution.

Effect of MgO on the Composition, Structure and Properties of Alite-Calcium Strontium Sulphoaluminate Cement

The influence of MgO on the composition, structure and properties of alite-calcium strontium sulphoaluminate cement were investigated by means of X-ray diffraction, SEM–EDS and light analysis. The results show that when the mass fraction of MgO is 1~5%, the early strength of cement can be enhanced significantly. The optimal content of MgO in the cement clinker is 2% and the compressive strengths of the cement at 3, 28 d are 64.3, 103.6 MPa respectively. A suitable amount of MgO can promote the formation of C1.5Sr2.5A3 , while the formation of C1.5Sr2.5A3 can be hindered if the content of MgO is excessive. The existence of MgO can improve the formation of C3S, increasing the mechanical property of the cement. Compared with the Portland cement, alite-calcium strontium sulphoaluminate cement has a higher capacity to dissolve MgO, which indicates that low-quality high-magnesium limestone can be efficiently used in the cement production.

Effect and Solid Solution Mechanism of Co<sub>2</sub>O<sub>3</sub> during C<sub>3</sub>S Formation

C3S is one of the most important mineral phases in silicate cement clinker; alternative ions could be solidified into C3S crystal lattice. Therefore, the research on solid solution mechanism was studied, which was about C3S doped with ions, Meanwhile, the achievement of this paper could be taken as a guidance for cement clinker industry. The effect and solid solution mechanism of Co2O3 during C3S formation were studied by means of chemical analysis, XRD and phase diagram analysis. The results show that when Co2O3 additive was less than 1.5% in mass, the content of f-CaO increased with the increase of Co2O3, and the formation rate of C3S was accelerated by Co2O3; when Co2O3 addition exceeded 1.5%, the content of f-CaO decreased with the increase of Co2O3.By the least square method and defined f-CaO, the molecular formula that Co2O3 solidified in C3S could be deduced: (Ca3-0.86x Co0.86x) (Si1-0.14xCo0.14x) O5 (x=0.0209).

Formation of Tricalcium Silicate Prepared by Electric and Microwave Sintering

A microwave sintering method was used to prepare C3S from Ca(OH)2, SiO2 and MexOy. f-CaO assay, X-ray diffraction and SEM were used to characterize the sintered samples.The results indicated that ion oxides played a very important role in C3S formation in conventional sintering, the use of MexOy as an additive was so effective in promoting C3S formation. The experimental results showed that samples were heated at an electric heating temperature(1500°C) and then further sintered with microwave for 30~60 min, tricalcium silicate could be formed with kilogram step. The new burning technique can greatly increase the forming speed of tricalcium silicate, MnO2, CuO and Ni2O3 could enhance the microwave sintering.

Effect of grain size of CaCO3 and SiO2 on the formation of C3S under different conditions

The effect of grain size of CaCO3 and SiO2 on the formation of C3S under various conditions, such as rapid heating rate(800 °C/min), normal heating rate(30 °C/min) and in the presence or absence of ZnO, was studied. The results show that the decomposition temperature of CaCO3, the temperature of appearance of liquid phase and the f-CaO content descend when the grain size of CaCO3 and SiO2 becomes smaller, which attributes to the reactive activity enhancement of powders due to the decrease of the particle size. When the grain size of CaCO3 and SiO2 is below 1 μm, the rate of the formation of C3S is greatly raised. A rapid sintering rate and the presence of ZnO have an important effect on the formation of C3S and can lower the temperature of the formation of C3S by about 50 °C.

Formation of Portland clinker—studies on synthetic raw meals

Synopsis On a series of laboratory made raw meals that contained only the four main oxides CaO, SiO2, Al2O3 and Fe2O3the sequence of reactions leading to the formation of Portland clinker was studied. Pellets made from raw meals of different composition were heated to different temperatures and analysed after quenching in air. It was found that the sequence of reactions taking place in the burning process and the temperatures at which new phases became detectable were virtually independent of the A/F ratio (Al2O3/Fe2O3) in the raw meal whereas the rate of C2S and C3S formation was distinctly accelerated with increasing iron content.