Utilization of red mud as raw material in the production of field road cement

Abstract

The total utilization amount of red mud is limited due to its high content of alkali, heavy metals and naturally occurring radioactive element. In order to rationalize the use of red mud, a typical field road cement using dealkalized red mud (content of alkali lower than 1%) as raw material was firstly prepared in this paper. Then, a preliminary research on the radioactivity of the red mud based field road cement has been carried out. For that reason, two samples of raw materials were prepared. One was with ordinary raw materials, as the control group (CG), the other was with 23w % red mud, as the experimental group (EG). The clinkers were acquired by sintering the above two raw materials at 1 400 °C. Subsequently, the two types of cement prepared by the above two kinds of clinkers were tested by measuring the normal consistency, setting time, mechanical strength and drying shrinkage. Meanwhile, the hydration products of the two types of cement were examined by XRD analysis at the curing age of 6 hours, 1, 3, 7, and 28 days, respectively. The radioactivity of the two kinds of cement clinkers was then measured by gamma-ray spectrometry. The experimental results indicate that the main mineralogical phases components in the EG field road cement clinkers are C₃S, C₂S, and C₄AF, the 28 days flexural and compressive strength of the EG field road cement mortars could be up to 8.45 and 53.2 MPa, respectively. The radioactive measuring results of the EG field road cement show that the value of radium equivalent activity index (Ra_eq) is 254.8 Bq/Kg^-1, which is lower than the upper limit.

Keywords

red mud / field road cement / preparation / hydration / sintering / radioactivity

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