Development of a new high-performance belite cement

（1）间隙熔体的结晶机理：首次发现了水泥熟料在冷却过程中发生了分步结晶。这种反应原则上决定了晶体和熔体的化学成分。以Ca_2SiO_4（C_2S）-Ca_2AlFeO_5伪二元系为例，在1375 ~ 1635℃温度范围内，C_2S固溶体Ca_2Al_（10.41）Fe_（0.5905）与熔体共存。在1375℃以上，C2 S（ss）和熔体两相稳定。因此，Ca2Al0.41FeO.59O5从熔体中结晶出来，因此共存熔体的化学组成中Fe 2 O3组分变差。(2)铁铝酸钙的带状结构，记录了结晶过程的信息：由于分离结晶的作用，铁铝酸钙晶体呈现带状结构，Al/（Al+Fe）值从核心向边缘逐渐增大。铝酸三钙固溶体最终从差异化熔体中结晶出来。(3)铝酸三钙的阳离子取代：掺杂Na，K，Mg，Fe和Si的铝酸三钙的化学式为（Na，K）2x（Ca，Mg）3-x-y[（Al，Fe）1-ySiy]206（0 μ x<0.158，0 μ y<0.136）。(4)取代离子对铁铝酸钙和贝利特稳定相的影响：铁铝酸钙的晶体结构与Al/（Al+Fe）值（=x）有关。0.235 μ x <0.7的空间群为Ibm 2。随着杂质氧化物浓度的增加，α' -向β-转变的起始温度从680℃逐渐降低到室温以下。

In the present research, we have obtained the following results(1) Crystallization mechanism of interstitial melts : we have found, for the first time, the occurrence of fractional crystallization in cement clinkers during cooling. This reaction, in principle, determines the chemical compositions of the crystals and melts. In the pseudobinary system Ca2SiO4(C2S)-Ca2AlFeO5, for example, C2S solid solution, Ca2A10.41Fe0.5905, and melt coexisted at temperatures between 1375 and 1635℃. At temperatures above 1375℃, the two phases of C2S(ss) and melt was stable. Accordingly, Ca2Al0.41FeO.5905 crystallize out of the melt, thus the chemical composition of the coexisting melt becomes poor in Fe2O3 component.(2) Zonal structure of calcium aluminoferrite, which records the information on the crystallization process : As the result of the fractional crystallization, the crystals of calcium aluminoferrite showed the zonal structure, the Al/(Al+Fe) values of which seadily increases from the cores toward the rims. Tricalcium aluminate solid solutions eventually crystallize out of the differentiated melt.(3) Cationic substitution of tricalcium aluminates : the chemical formula of the tricalcium aluminate doped with Na, K, Mg, Fe and Si has been developed to be (Na, K)2x(Ca, Mg)3-x-y[(Al, Fe)1-ySiy]206 (0≦x<0.158, 0≦y<0.136).(4) Effect of substituent ions on the stable phases of calcium aluminoferrite and belite : The crystal structure of calcium aluminoferrite was dependent on the Al/(Al+Fe) value (=x). with 0≦x<0.235, space group was Pcmn, while, it was Ibm2 with 0.235≦x<0.7. The starting temperature of the α' -to-βtransformation steadily decreased from 680℃ to below the ambient temperature with increasing concentration of foreign oxides.