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The effect of representative admixtures on hexavalent chromium concentration in concrete was also evaluated, but technical limitations made evaluation difficult. Soluble chromium levels in cement ranged from 0.225 mg/kg in the US sample to 0.036 mg/kg in the Singapore sample.
Hexavalent Chromium in Cement Manufacturing: Literature Review. With regard to chromium and health and safety aspects, the water-soluble compounds of chromium in cement are most relevant, specifically compounds of the form Cr (VI). Chromium in the cement can originate from: 1) raw materials or fuel, 2) magnesia-chrome kiln refractory brick, if ...
Durability and service life of concrete structures can be endangered by chloride ions. Two phenomena help to keep control of chloride effects. On one hand cements are able to bind chloride ions by their aluminate clinker phases or by the clinker substituting materials. On the other hand resistivity of concrete against chloride penetration can be improved by careful …
Raw materials for manufacture of Portland cement in Lukavac contain traces of chromium.Chromium in the cement can originate from: 1) raw materials or fuel, 2) magnesia-chrome kiln refractory brick, if used, 3) wear metal from raw mill grinding process, if chromium alloys are used, and 4) additions such
INTRODUCTION. The purpose of this review is to summarize information related to hexavalent chromium, Cr (VI), in the portland cement industry. The catalyst for initiating this project was the content restrictions and labeling/marketing of cements based on the level of Cr (VI) in cement in Europe, and the potential for a similar situation in North America in the near …
Chloride binding in concrete has been investigated by analysing pore solution expressed from cement paste specimens using a pore press. For chlorides introduced at the time of mixing, cement type, the type and proportion of cement replacement material, the chloride salt and total chloride content were found to be the most important factors governing binding.
Abstract and Figures. In this paper, the effect of FeSO4.7H2O and SnCl2.2H2O on Cr (VI) reduction is compared by measuring Cr (VI) content before and after adding of reducing additives in cement ...
Chromium in the cement can originate from: 1) raw materials or fuel, 2) magnesia-chrome kiln refractory brick, if used, 3) wear metal from raw mill grinding process, if chromium alloys are used, and 4) additions such as gypsum, pozzolans, ground granulated blast furnace slag, mineral components, and cement kiln dust.
Feb 25, 2015 0183 32 The comparative analysis was carried out to know the effect of chromium hexavalent reducing additives such as ferrous sulphate FeSO 47H 2 O and stannous chloride SnCl 22H 2 O on the reduction of Cr VI by measurement of Cr VI before and after adding the reducing agent in cement sampl The results obtained after the action of reducing ....
The method according to claim 1 wherein the antimony(III) inorganic salt is selected from the group consisting of chloride, fluoride, carbonate, sulphate, hydroxide, sulphite, thiosulphate, nitrate, nitrite, thiocyanate, formiate, bromide, iodide, acetate, and phosphate salt. ... chromium reducer, which can be used in cement grinding especially ...
The effect of representative admixtures on hexavalent chromium concentration in concrete was also evaluated, but technical limitations made evaluation difficult. Soluble chromium levels in cement ranged from 0.225 mg/kg in the US sample to 0.036 mg/kg in the Singapore sample. ... Fresh US concrete, with 1.27 mg/kg hexavalent chromium, contained ...
grinding and during cement storage. This requires the use of very high dosages of ferrous sulphate, causing costs to be higher than expected as well as triggering unfavourable side-effects (formation of red spots on the concrete surfaces, due to the characteristic colour of Fe3+ compounds, is very frequent).
The amount of chloride in the cement is controlled during the manufacturing process and is defined as 0.01% or less by weight of cement and also specified in the literature as 0.01% (Neville, 2004). Total chloride in concrete is measured for each concrete mix according to BS 1881-124 (BS1881 Part 124, 1988 BS1881 Part 124, 1988).
Due to increasing environmental and health-related concerns, the amount of hexavalent chromium found in portland cement is coming under increasing scrutiny. Hexavalent chromium has been classified as a carcinogen, and its release into the air or groundwater is regulated and controlled under many Federal and State regulations. In addition to carcinogenic …
With regard to chromium and health and safety aspects, the water-soluble compounds of chromium in cement are most relevant, specifically compounds of the form Cr (VI). Chromium in the cement can originate from: 1) raw materials or fuel, 2) magnesia-chrome kiln refractory brick, if used, 3) wear metal from raw mill grinding process, if chromium alloys are used, and 4) …
control concrete having a low w/b of 0.35 has a chloride permeability greater than that of concrete with high w/b of 0.65 and containing glass powder . [22] Shayan et al. have shown that at constant water to binder mass ratio, the addi-tion of 20% of GP (particle size . 10 microns) significantly reduces the chloride ion permeability of concrete .
Cement grinding operation may be performed in one of the following mill setups. Ball and tube mills. Vertical Roller Mills (VRM). Roller press with Ball mill. Ball Mill. Ball mills with high efficiency separators have been used for cement grinding in cement plants all these years. Ball mill is a cylinder rotating at about 70-80% of critical ...
Keywords: Cement, FTIR, Reducing Agent, Spectrophotometer, Water Soluble Cr (VI) 1. Introduction The hexavalent chromium is of individual importance among many trace elements present in Portland cements 1. Because of extreme toxicity of Cr(VI) which cannot be completely stabilized in cement matrix, which gener-
Hexavalent chromium in cement, 15 years later. All author/Mapei. The object of this paper is to review, more than fifteen years after the introduction of directive 2003/53/EC, the technological aspects of the formation and reduction of soluble chromates in Portland cements. Since January 2005, following the implementation of directive 2003/53 ...
Chromium in the cement can originate from: 1) raw materials or fuel, 2) magnesia-chrome kiln refractory brick, if used, 3) wear metal from raw mill grinding process, if chromium alloys are used ...
The removal of hexavalent chromium by electrocoagulation involves two stages: the reduction of Cr(VI) ... High current efficiencies, greater than , are obtained for the anode oxidation due to the synergistic effect of chloride ions and protons, which catalyze the anode dissolution, especially at the higher concentrations of H 2 SO 4.
White dealing with the durability aspect of concrete, the chloride effect on concrete is the most important factor as it causes the corrosion of reinforcement of concrete. The statistical studies have shown that more than 40% structures have failed due to the corrosion of reinforcement steel. Due to high alkaline nature of calcium hydroxide ...
Portland cement–steel composites frequently take up chloride from their service environment. The degradation processes and test methods are described through a critical review of the literature. Plain cement paste is not much affected by chloride except for increased solubilisation of cement solids, but chloride is detrimental to the passivation of embedded …
Your contribution will be forwarded to the A study of the effect of chloride binding on service life author(s) for a reply and, if considered appropriate by predictions. Cement and Concrete Research 30(8): 1215– the editorial panel, will be published as a discussion in a 1223. future issue of the journal.
Jun 01, 1994· Studies at a California cement plant showed that more than half of the hexavalent chromium in the cement was contributed by the grinding media in the finish mill. Attempts to reduce the chromium to its benign trivalent form with ferrous sulfate failed in full-scale trial grinds, due to oxidation of the ferrous iron.
