25 posts
clinker litrweight
hello friends. friends sometimes we face the problem of low litrweight but still having clinker in good shape and no brown core but clinker found in very porous form. y this happend that clinker shape and color good but litre weight low.
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537 posts
Re: clinker litrweight
Hello Prisoner,
About a year ago, I answered a similar question with the following explanation;-
"I found that large dry-process kilns are generally very 'dusty'. i.e. large amounts of clinker dust returning with the secondary air. This dust may have already passed several times through the burning zone and therefore has zero free lime content and is composed mainly of alite crystals.
The dust forms an outer coating on clinker nodules which is typically 1-2mm thick. Under the microscope, it can be seen that this layer is extremely porous and is built up from individual dust particles cemented together in a sponge-like structure by thin bridges of liquid phase (originating from coal ash melted in the flame).
At first glance you might dismiss a 1-2mm thick layer as inconsequential, but the smaller the nodule selected for the litreweight test, the stronger the influence that this type of layer has on the overall nodule density. For example, if nodules with an average diameter of say 6mm are selected, a 1mm layer represents 70% of the total volume of the nodule! Even for a 10mm nodule, a 1mm layer comprises almost half of the volume of the whole nodule. So, the influence of a very thin, low-density layer is very significant.
As a result, such clinker nodules result in a low litreweight while at the same time a low free lime content."
Hope this helps,
Ted.
25 posts
537 posts
Re: clinker litrweight
Hello Prisoner,
No, the quality of the clinker is not greatly affected by the dusty layer, but this type of clinker tends to become more dusty as it is transported. The outer friable layers abrade away easily and create additional dust. This dust component is usually composed of large alite crystals which are more difficult to grind.
See also;- "Texture and grindability of the dust component in portland cement clinker", I. Maki, S. Ito, K. Maeda and K. Fukuda, Cement and Concrete Research,Volume 24, Issue 3, 1994, Pages 497-502
The authors orf that paper claim that, "The dust component is inferior in grindability to the outer part of clinker nodules. This is due presumably to the difference in grinding hysteresis".
It must be remembered that this type of clinker is the result of a dusty kiln atmosphere which can also promote 'snowmen' in the cooler and disrupt the heat profile of the burning zone. This can certainly affect clinker quality.
Regards,
Ted.