The question has been raised as to whether vacuum treatment results in a higher grade of concrete, so that a higher class of strength may be utilized for the surface layer or possibly for the whole cross section, and, if so, what recommendations should then be made for the procedure to be adopted in such cases. The objective of the investigation described in the present paper was to obtain the basic data required for answering this question. Concrete slabs, about 600 by 700 mm in surface area and 100, 200, or 300 mm in thickness, have been poured and vacumm-treated. Four core cylinders, 100 mm in diameter, were drilled from each slab. The cylinders taken from the slabs 200 and 300 mm in thickness were cut so as to produce test specimens 100 mm in height, and thus to enable the strength of the concrete to be determined at different levels. The increase in strength did not completely correspond to the quantity of water removed from the concrete, but seemed to continue until a certain definite quantity of water - a threshold value - has been removed. No marked improvement in strength appeared to take place after that value had been reached. The magnitude of the threshold value is dependent on the thickness of the slab, the type of concrete, etc. It was considered that the increase in the strength of the concrete in the surface layer (100 mm in thickness) corresponded to three classes of strength. Therefore, it is reasonable that this increase in strength should be taken into account in choosing the grade of concrete for floors poured in a single layer (see the Swedish house construction code HusAMA 1972). Furthermore, it appears reasonable, at least for a thickness of 100 mm, that a higher class of strength should be utilized in design for the whole cross section.
Cement och BetonginstitutDrottning Kristinas Vaeg 26
Stockholm 70, Sweden
- DAHL, G
- Publication Date: 1975
- Features: Figures; Tables;
- Pagination: 15 p.
- TRT Terms: Bridge decks; Concrete; Crash investigation; Floors; Strength of materials; Studies; Trimming; Vacuum; Water
- Uncontrolled Terms: Removal
- Subject Areas: Highways; Materials; Safety and Human Factors;
- Accession Number: 00125446
- Record Type: Publication
- Report/Paper Numbers: 7:75
- Files: TRIS
- Created Date: Nov 5 1975 12:00AM