Mass loss evaluation of CSAB clinker raw materials composed with aluminum anodization sludge

Portland cement science is well established in Brazil and in the world; however, the development of calcium sulfoaluminate belite (CSAB) cements, considered a low-environmental impact material, is still in its initial stages relative to cement Portland abroad and there are even fewer studies nationally. One concern regarding the production of CSAB cements is the high amount of sulfur in the raw materials. Excess sulfur in the feed-stock of Portland cement causes the increase of SO₂ emissions, a dampening the efficiency of the pre-heater in the clinker factory, in addition to causing the formation of bonding rings inside the kiln. The viability of the production of CSAB cement depends on the availability of raw materials at low cost, preferably with the use of an alternative industrial waste. Thus, the aim of this work is to analyze the mass loss of lab-made CSAB mixtures up to a temperature of 1450ºC, in order to verify the decomposition of sulfated compounds and to evaluate the possibility of replacing bauxite by an alternative source of Al₂O₃, namely by aluminum anodizing sludge (AAS) residue, which presents itself as an interesting raw-material for the production of CSAB clinker due to its high content of alumina. Mixtures made with pure chemicals, AAS residue and conventional materials were produced. Raw materials were proportioned based on equations formation of compounds synthetic from the mixture oxides composition. To check the mass loss, thermogravimetric analyzes were performed. It was concluded that the maximum temperature for CSAB clinker production should be close to 1250ºC to avoid decomposition of sulfur-containing phases and their related SO₂ emissions.

sulfoaluminate cement; belite cement; CO₂ emissions; co-processing