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Description: Reviews the effects of lead, molybdenum, antimony, copper, cadmium, beryllium, titanium, vanadium, chromium, manganese, nickel, and zinc in quantities of 0.5% or 0.25% by mass on performance characteristics of clinker. Properties examined include clinker hardness (grindability), setting time, and strength development. The effects of these metals on clinker phase distribution and microstructure are also examined.
The effect of minor elements on the production and performance of portland cement
have been presented in this report. The elements studied are lead, molybdenum, antimony,
copper, cadmium, beryllium, titanium, vanadium, chromium, manganese, nickel, and zinc. The
elements are added at 0.5% and 0.25% by mass as single metals and multiple metals to the raw
mix. To simulate practical scenarios, industrial by-products with known metal concentration,
such as copper slag, sinter mix, and catalyst fines have also been studied.
Clinkers produced with single metal exhibited increased hardness. The clinkers did not exhibit
any burnability problems; distribution of C3S, C2S, C3A, and C4AF were within the normal
range without any free-lime increase. However, titanium and antimony enhanced the
formation of C3Aat the expense of C4AF, whereas barium and beryllium increased C4AF and
reduced C3A. Alite crystals in most clinkers were decomposed and clustered as opposed to
isolated, individual crystals. The belites were rounded but did form ragged edges. Amajority
of the metals were found concentrated into the aluminoferrite phases except vanadium, and
possibly chromium and lead, which were equally distributed in the aluminoferrite and silicate
phases. Zinc, copper, titanium, and beryllium delayed cement hydration and caused longer
setting times that affected the strengths. Beryllium at 0.5% addition was a severe retarder that
gave long setting times and very low strengths.
Clinkers made with multiple metals were also harder to grind. The distribution of major
phases – C3S, C2S, C3A, and C4AF was appropriate with negligible free lime; the exception
being nickel-vanadium-antimony that enhanced C3A at the expense of C4AF. Nickelvanadium-
antimony also formed irregular belite with wide lamellae. Other multiple metals
decomposed the alite crystals, and produced slightly irregular and ragged belite, except
copper-nickel-zinc which had very little effect on both alite and belite formation. Multiple
metals imparted varying effects on the early hydration of cement, but all produced high early
strengths except for nickel-vanadium-antimony, which delayed setting and reduced cement
strength; copper-lead-zinc accelerated the setting.
Addition of industrial by-products such as copper slag, sinter mix, and catalyst fines
affected the crystallinity of clinker. Alite crystals were decomposed and cannibalized, and
belite crystals were irregular with ragged edges. The clinkers were harder to grind. Paste
strengths with all by-products were notably reduced.
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