dik
Structural
- Apr 13, 2001
- 26,037
I'm looking for information on the relationship between concrete strength and abrasin resistance. Does anyone have a link that has published information. I realise that concrete strength is only one of several factors affecting concrete abrasion resistance. The concrete I'm dealing with has about 25% flyash substitution.
A second question related to the first and more of a puzzle:
A large mass of concrete was placed and the specs required that a layer of sand/cement grout be placed between this and the next layer. The layer of grout was out of spec for strength by about 60% but no cylinders were taken. A second layer of mass concrete was placed over the cement/sand grout.
The grout layer was hydroblasted to remove it and in the process, the upper layer of new mass concrete was eroded by the water jet. Water pressure was 12,500 psi (common). The mass concrete on the lower layer was, with the exception of minor surface abrasion, unaffected. It is puzzling why the mass concrete over the grout joint was severely affected; under the same hydroblasting effort as the mass concrete below, the top mass concrete layer was gouged approximately 3/4" deep. There was a distinct change in colouration between the concrete matrix of the outside surface and the inner surface. The inner surface was a dark green-grey colour and the exterior surface was noticeably lighter in colour. Concrete specified was 35MPa with 25% flyash. Both layers of mass concrete were in excess of two months old. The problem appears to be extensive; an area 50' away had a similar erosion with a similar hydroblasting effort and both mass concrete layers had been cast approx 4 months ago.
Can anyone offer a suggestion about why there would be an apparent separation within the concrete mix?
Dik
A second question related to the first and more of a puzzle:
A large mass of concrete was placed and the specs required that a layer of sand/cement grout be placed between this and the next layer. The layer of grout was out of spec for strength by about 60% but no cylinders were taken. A second layer of mass concrete was placed over the cement/sand grout.
The grout layer was hydroblasted to remove it and in the process, the upper layer of new mass concrete was eroded by the water jet. Water pressure was 12,500 psi (common). The mass concrete on the lower layer was, with the exception of minor surface abrasion, unaffected. It is puzzling why the mass concrete over the grout joint was severely affected; under the same hydroblasting effort as the mass concrete below, the top mass concrete layer was gouged approximately 3/4" deep. There was a distinct change in colouration between the concrete matrix of the outside surface and the inner surface. The inner surface was a dark green-grey colour and the exterior surface was noticeably lighter in colour. Concrete specified was 35MPa with 25% flyash. Both layers of mass concrete were in excess of two months old. The problem appears to be extensive; an area 50' away had a similar erosion with a similar hydroblasting effort and both mass concrete layers had been cast approx 4 months ago.
Can anyone offer a suggestion about why there would be an apparent separation within the concrete mix?
Dik
