Examples of polished plane sections with the PetroPlaner. Above left is a surface prepared for air -void analysis using the RapidAir system according to ASTM C 457 or EN 480-11 after contrast enhancement. At center and right are examples of surfaces prepared for forensic, petrographic analysis.
In preparing polished plane sections for microscopical air-void analysis according to ASTM C457 or EN 480-11, it is crucial that the polishing be of very high quality. Both the paste and the aggregates have to be polished to exactly the same level and no erosion of the paste has to occur. In order to measure reliably the correct chord length of each air void, it is extremely important that the individual air voids have clear and sharp edges without any degradation. Otherwise, the results of the air-void analysis will be erroneous.
Polishing of concrete specimens for air-void analysis by ASTM C457 or EN 480-11 is especially difficult if:
- The paste is weak due to low maturity, poor curing, or a high water-cement ratio
- The paste is deteriorated
- The aggregates are extremely hard, having higher resistance to abrasion than the paste
- The concrete has a high air content causing erosion of the paste between individual air voids