Recovery of ilmenite mud as an additive in commercial Portland cements.

This work is focused on the manufacture of commercial cement using as additive ilmenite mud, a waste generated during TiO 2 pigment production. The cements were produced by adding different proportions of mud (2.5, 5 and 10 wt%) to ordinary Portland cement (OPC). The ilmenite mud and the ilmenite mud cements (IMCs) were characterised physico-chemically by X-ray fluorescence (XRF), inductively coupled plasma mass spectrometry (ICP-MS) and X-ray diffraction (XRD). Moreover, the technological properties of the IMCs were evaluated and compared with a reference material (OPC). Since waste from the TiO 2 industry is classified as a NORM (naturally occurring radioactive material), the concentrations of radionuclides were measured by high-resolution low-background gamma and alpha spectrometry techniques. Finally, the TCLP leaching test (Toxicity Characteristic Leaching Procedure, USEPA), the radiological index ("I") and the Ra equivalent concentration were also calculated to evaluate the environmental risks. As a final conclusion, it can be pointed out that the addition of ilmenite mud to OPC plays a beneficial role since it reduces the heat of hydration, the final setting time, the expansion and the linear retraction compared to standard OPC. The compression strength improves with the addition of up to 5 wt% mud. Moreover, the environmental impact of IMC2.5 and IMC5 can be considered negligible.