Burning Alite-Rich Portland Clinker And Study On Doped Alite

Alite-rich portland clinker (ARPC) was researched, in which the content of alite was increased to 70%. The relationships between clinkering process with doping technology and its properties with the Alite's microstructure were investigate. The ARPC with different mineral match and doped different impurities singly or complexly were experimentally burnt. The impurities were deal with anions and industrial wastes. Single minerals C3S and its solid solutions were synthesized. With chemical analysis, petrographic analysis, physical properties tests, scanning electronic microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), thermo analysis (TA), optimized mineral match, the doping technology, clinker's properties and microstructure, the polymorph of alite were studied.The experimental result and the lithofacies map of CaO-SiO2-Al2O3-Fe2O3 indicated that LSF is more correlative with burnability than KH. In the range of (KH=0.98, SM=1.90) ~ (KH=0.94, SM=3.00) and with a proper IM, the ARPC can be designed with good burnability. This shows that ARPC is applicability with raw materials. The proportions of ARPC have a wid proportion scope, and the high KH, high SM and high IM can make ARPC good burnability.To common portland clinker, the module SM was used to control the content of liquid in clinkering process, and IM was used to control the viscidity. Based on the understanding, common clinker with good burnability should be low SM and IM values. But the liquid content was more important in ARPC burning system, because the liquid phase is fewer than in common clinker system. In the case of burning ARPC, for a high SM (often greater than 2.0), the influence of liquid content variety is more evident than the effect of viscidity variety on the burnability caused by change of IM. So the match of high SM with low IM can not make good burnability.Doping gypsum and fluorite into ARPC, whether singly or doubly, they all could only accelerate the combination of f-CaO at low temperature, and were little effect at high temperature. If doping sulfur only, especially, the residue of f-CaO in ARPC burnt at high temperature were more than it in control sample that doped no any impurity, which may be related with the high volatility of sulphate. The mineralizers gypsum and fluorite were more suitable for burning at low temperature.Doping phosphor could reduce the residue of free lime in ARPC burnt at normal clinkering temperature. But it is not efficiency at low temperature. Doping phosphor singly is more fit for high temperature burning process. Doping phosphor and fluorine doubly could accelerate the clinkering ARPC at all range of burning temperature from 1250°C~1500°C. Doping phosphor and fluorine doubly is a technology for new dry process.The researched wastes were deal with the phosphor-making slag (PMS), blast furnace slag (BFS), chrome-making slag (CrMS), calcium rich flay ash (CRFA), steel-making slag (SMS) and(RM). Among all the wastes, PMS and SMS can efficiently accelerate clinkering process, and the PMS was more efficiency. Mixing PMS singly into raw meal, the burnability of ARPC could be significantly ameliorated; the clinkering of ARPC could be completed at industrial burning temperature. RM, BFS and CRFA had not effective influence on the burnability. The CrMS even had negative action. The SMS and PMS cooperated with F and P2O5 were most efficient.A function was put forward to calculate the conversion ratio of CaO transformed to C3S in clinker system. The apparent activation energies of C3S formation for series ARPC systems were calculated. They could be used to compare the activities of series clinkering systems. Doping some industrial wastes, fluorine and phosphor anions singly or compositely can decrease the apparent activation energy. The reason may be the fluxing function of the wastes and the anions. The anions improved the mass transferability and accelerated the crystal core formation and growth.Doping phosphor singly, the strengths of ARPC were heightened at ages of 3d and 7d, and were same as control sample at 28d. The phosphor'concentrations have a proper range in the ARPC, very low and very high contents cannot improve even decrease the strength. Double mixing phosphor and fluorine within a proper proportion, the strengths of experimental samples were hither distinctly than the control samples. Doping fluorine, sulfur and phosphor at proper concentrations, the action was similar as doping phosphor singly, and was not as efficient as dual doping of phosphor and fluorine.Doping phosphor with compounds CaHPO4, Ca(PO4), P2O5 ways made ARPC different strengths. The early strength of the samples mixing CaHPO4 were lower a little than that mixing Ca(PO4) or P2O5, then their strengths after 28d were same. The strengths of the sample doped PMS were higher than doping the three compounds. Dual doping CaF2 and PMS, the strengths could be heightened further. Mixing SMS singly could not increase the strengths. Doping P2O5 and CaF2 with SMS, the strengths can get advances.The volatilities of the anions were different in clinkering process. The Fluoride and phosphate had lower volatilities than sulfate. The sequence of anion's volatilities was: sulfur>fluorine> phosphor.The alite and intermediate phase in experimental clinkers contained many impurities. MgO mainly solute into matrix, and a few of went into alite. Average K2O was into alite and matrix approximately. The solution ratio of P2O5 in alite and matrix were about 2:1. When sulfur dissolved into alite, the concentration of P2O5 in alite was increase and it was decrease in intermediate phase a few.With the rising of burning temperature, the concentration of P2O5 in alite decreased a few and it increased a few in matrixes. The solution ratio between them was still about 2:1. The solid solute content of Fe2O3, Al2O3 and other ions were depressed with the temperature rising. P2O5 distributes averagely at the alite section, does not beneficiate in center or border.If a P5+ ion went into alite cells, it replaced a Si4+ ion. Because of the difference of valences, the electronic defects need be balanced by other defect reactions, such as a positive three-valencecation (Al3+, Fe3+) replaces a Si4+, or a negative 1-valence anion (F") replaces a O2- anion, or a O2-vacancy forms. On condition that ions Fe3+, Al3+, P5+, F- coexisted in alite, based on the compares with thire chemical structural parameters, the replacements between the Fe3+ and Ca2+, Al3+and Si4+, P5+ and Si4+ , F- and O2- were most able to take place in the all guessed defect reactions. The solid solutions caused alite crystal lattice adjustment and distortion.The lattice constant varies caused by impurity defects were calculated for experimental Alites. They accorded with the values of the alite stabilized by ZnO, which reported in some literatures. The calculation results guessed that the symmetry of doping Alite could be advanced. And the some experimental alite was able to exist at rhomboheral pattern stably. The XRD and TA firmed the conclusion.ARPC have higher strength than ordinary clinker. The one of the important reason is the rich content of alite, the other is most of alite in ARPC existing at more symmetric crystal pattern, R polymorph, which made the alite more efficient hydrate activity.