The effect of the combined addition of copper, lithium and sulphur on the formation of Portland cement clinker

Both copper and lithium act as strong fluxes and lower the temperature of the clinker melt formation. Sulphur promotes the stabilisation of more hydraulically active modification of alite M1. It is expected that this combination could produce an alite clinker at significantly lower temperatures with high quality technological parameters. In this paper, the effect of combined oxides of copper, lithium and sulphur addition on the phase composition and clinker structure of Portland cement was investigated. The reference raw meal was prepared from common cement raw materials. Each of the mentioned oxides was added to the reference raw meal in two different concentrations, and 8 combinations were prepared. Chemically pure compounds (NH4)2SO4, CuO and Li2CO3 were used as a source of these oxides. The raw meals were burned to equilibrium at 1450 degrees C. Their phase composition was determined by X-ray diffraction analysis, the microstructure was monitored by optical microscopy, and the microchemistry of the clinker phases was observed by electron microscopy with EDS analysis. It was found that in samples with high lithium or copper content, there is an increase in belite and free lime at the expense of alite. The combination of Cu + Li has the most negative effect, followed by Li alone and Cu alone. The higher SO3 content slightly offsets this negative effect. Clinker is the main intermediate in the production of Portland cement. It is formed at high temperatures in a rotary kiln and its main component is the mineral alite - tricalcium silicate. Alite crystallises in several polymorphic modifications, and sulphur stabilises the modification that increases cement strength. Both copper and lithium act as strong fluxes and lower the temperature of the clinker melt formation. The addition of a combination of these 3 elements to the raw meal for clinker burning is expected to lower the melt formation temperature, and clinker with a high alite content will be formed at lower temperatures than normal. This would both save energy consumption for burning and reduce CO2 emissions in cement production. In this paper, the effect of combined of copper, lithium, and sulphur addition on the phase composition and clinker structure of Portland cement was investigated. The reference raw meal was prepared from common cement raw materials, two limestones, clay shale and Fe correction. Each of the mentioned elements was added to the reference raw meal in two different concentrations, and 8 combinations were prepared. Chemically pure compounds (NH4)2SO4, CuO, and Li2CO3 were used as a source of these elements. The raw meals were burned at 1450 degrees C. Their phase composition was determined by X-ray diffraction analysis, the microstructure was monitored by optical microscopy, and the microchemistry of the clinker phases was observed by electron microscopy with energy dispersive spectroscopy. It was found that in samples with high lithium or copper content, there is an decrease in alite. The combination of Cu + Li has the most negative effect, followed by Li alone and Cu alone. The higher sulphur content slightly offsets this negative effect. Finally, a clinker was prepared with the addition of these 3 dopants at a temperature of 1325 degrees C, 125 degrees C lower than in conventional industrial production, which had a high quality phase composition with a high alite content.