| In the21st century, traditional portland cement is still one of the most important building materials, because of its well building performance and more and more advanced production methods. But it has some shortcomings,such as lower early strength, the bulk shrinkage of hardening paste and high sintering temperature etc., which can not meet the requirements for special modern construction projects. The invention of new cement minerals can provide a basis for the development of new high-performance, low environmental load of cement and sustainable development of cement industry. Barium calcium sulphoaluminate cement is invented on the basis of sulphoaluminate cement, and it has better early strength, high strength and impermeability properties than sulphoaluminate cement. But the system is still not perfect because of its started relatively late. Iron phase of barium calcium sulphoaluminate cement clinker plays an important role in selection of raw materials and formation and performance of cement clinker.This article is studied using pure chemical reagents as raw materials under laboratory conditions. Firstly, influence of5%of different iron phase composition on formation and performance of barium calcium sulphoaluminate cement was studied, and according to experimental results to analyze the impact of the law and get the best iron phase composition ratio. On this basis, this article also studied the different iron phase content for barium calcium sulphoaluminate cement formation and performance. Barium calcium sulphoaluminate cement clinker, hydration microstructure and composition were characterized by used XRD, SEM-EDS and thermal analysis etc.analytical testing methods.The results show that:the iron phase in the process of cement clinker, which can effectively reduce the decomposition temperature of calcium carbonate. From the XRD analysis can be seen that Ba2+replaces Ca2+occurred replacement substitution reaction to generate barium calcium sulphoaluminate mineral with increasing temperature in the calcination process.The main diffraction peak of d values of barium calcium sulphoaluminate mineral is gradually increasing from3.7543,3.7925,3.7945to3.7957, with the iron phase of Fe and Al molar ratio increasing in the same temperature. From the SEM-EDS analysis of clinker minerals we know these clinker minerals mainly generated a mass of rhombic dodecahedron of the C2.75B1.25A3S and round granular of the dicalcium silicate. Ba elements are mainly distributed in the barium calcium sulphoaluminate mineral region, and some been solid solution to C2S. Fe elements that been formed an iron phase as solid solution play the role of the flux of minerals, which distributed in the between C2.75B1.25A3S and C2S grain. From the compressive strength, XRD analysis, SEM analysis shows that the iron phase composition of C4AF is the optimal. The compressive strength can reach up73.2MPa,97.9MPa and106.9MPa at1d,3d and28d curing ages.From the macroscopic view of these clinker minerals, they are changed from pale green to dark green gradually with the increase in the amount of iron phase. Also the density is increasing, grindability is getting worse. However the hydration strength is still better performance when the C4AF content of up to15%. The compressive strength can reach up73.2MPa,97.9MPa and106.9MPa at1d,3d and28d curing ages. Amount of iron phase can reduce the eutectic melting point of the system, increase the liquid content, reduce the liquid viscosity and effectively accelerate the migration of mineral ions to promote the formation and growth of the mineral. When the iron phase composition for C4AF iron phase was5%, early hydration and post-strength performed best.Combination of XRD and SEM analysis shows that the series of cement hydration process is as follows:C2.75B1.25A3S+H2Oâ†'BaSO4+CAH10+AH3and C2S+H2Oâ†'C-S-H+CH. |
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