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cement paste porosity
- Thread starter mizz
- Start date
Might it be that due to the finer grindage of modern cements, only part of it is reacting/properly mixing with the other components and such nodules be then more source of irregularity to infill than infilling partners? In such condition a more uniform mix might produce lesser porosity.
Also, might some of the components be pre-reacted or aged past the point of proper application? Or some way spoiled?
Also, might some of the components be pre-reacted or aged past the point of proper application? Or some way spoiled?
- Thread starter
- #3
yes, I do agree there is posibbility of not uniform mixes or leaching. However, I also carried out sorptivity test which shows reduction in absorption compared to cement paste only. Therefore, it hard to conclude due to different trend in porosity.
Then it sounds as if we are getting more shrinkage in the cement combination paste that in the cement paste.
If the materials are less absorptive, the matrix formed in the combined paste must be allowing the formation of some form of structured shrinkage with the bigger porositiy.
This points again to first a formation of the bigger matrix, the additions upon reactivity taking part, and gaining strength, and then shrinkage happening supported upon such bigger matrix.
If such is the case, ensuring such hardened matrix can't form beforehand would be the way to go.
If coming from over-reaction, the additions being too fine could be the cause, but the formation of structures before the proper time could point exactly the contrary way, too coarse grains promptly reacting at their surface and allowing the bridging.
In any case, for mixes of materials well known to the chemical experts, I would look at the granulometry of the materials (and purity of the water).
If the materials are less absorptive, the matrix formed in the combined paste must be allowing the formation of some form of structured shrinkage with the bigger porositiy.
This points again to first a formation of the bigger matrix, the additions upon reactivity taking part, and gaining strength, and then shrinkage happening supported upon such bigger matrix.
If such is the case, ensuring such hardened matrix can't form beforehand would be the way to go.
If coming from over-reaction, the additions being too fine could be the cause, but the formation of structures before the proper time could point exactly the contrary way, too coarse grains promptly reacting at their surface and allowing the bridging.
In any case, for mixes of materials well known to the chemical experts, I would look at the granulometry of the materials (and purity of the water).
concretemasonry
Structural
Take a look at the fineness of the cement (Blaine or other measure). The fine grinds will give a quicker reaction and change the paste structure.
There are many complex combinations of cement to balance the chemistry and fineness for the best performance for what is produced. There is not a simple answer to your question.
Much depends on the use of the cement and requirements for the paste properties. If you do not have enough volume, you will have to work within the current Types and variations that different manufacturers offer. If this is the case, contact a major cement supplier and talk to the technical lab people. They know more about cement properties and use since the involvement of international ownership and high tech research.
For many years, we used a totally non-spec cement for the production of manufactured concrete elements. It was between a Type I and a Type III with a little extra air and a very short initial set. It produced a product that was superior in end use to the standard ASTM Type categories. The cement companies also liked to produce it because it was a relatively constant demand product and could be produced in the off-season and ground when the inventory got low.
There are many complex combinations of cement to balance the chemistry and fineness for the best performance for what is produced. There is not a simple answer to your question.
Much depends on the use of the cement and requirements for the paste properties. If you do not have enough volume, you will have to work within the current Types and variations that different manufacturers offer. If this is the case, contact a major cement supplier and talk to the technical lab people. They know more about cement properties and use since the involvement of international ownership and high tech research.
For many years, we used a totally non-spec cement for the production of manufactured concrete elements. It was between a Type I and a Type III with a little extra air and a very short initial set. It produced a product that was superior in end use to the standard ASTM Type categories. The cement companies also liked to produce it because it was a relatively constant demand product and could be produced in the off-season and ground when the inventory got low.
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