Minerals as Cr (VI) Reducing Additives and their Impact on Cement Performance

Abstract: A potentially serious condition could occur when cement containing Cr (VI) comes into contact with the skin causing irritations and eczema. A common strategy to surmount this difficulty is to reduce hexavalent chromium in cement using a reducing agent in wet condition before putting to use cement-water paste. The objective of the present research work is to evaluate the effectiveness of various minerals as Cr (VI) reducing additives to Portland cement. The minerals used in the present study are bauxite, bentonite, attapulgite, china clay and jarosite. The Cr (VI) levels were tested using 1,5- diphenylcarbazide method at 540 nm on an UV-Visible spectrophotometer (according to the EN-196-10 method); the same were confirmed using ICP-OES technique. The physical testing of the cement mortar samples was carried out in order to understand the effect of these additives on cement quality. The mineral jarosite, was found to be the most efficient additive for reducing Cr (VI) in cement and also, it was observed to be storage stable for the longest period (up to 90 days). XRD and SEM studies reveal that no phase alterations took place compared to the original cement sample. Thus, jarosite emerges as a good reducing agent for the reduction of hexavalent chromium in cement at 3 % (w/w) solid dosage form, on account of its reduction efficacy, good storage stability, without impacting the physical properties of cement and its low cost