aggregate to resist hydraulic erosion 3

[joncum]

I trying to complete a spec for aggregate for a CIP concrete spillway/ stilling basin for a dam. The water velocity will approach 40 fps so abrasion is a concern. Since it's mass concrete, the concrete selected will not exceed f'c 5000 psi to control heat of hydration (grade 10,000 psi w/ silica fume probably would not be suitable).

The coarse aggegate should therefore be hard, high quality, durable rock. Can anyone suggest any ref. papers, manuals, previously use specs. for guidance re. rock description, minimum testing criteria etc?

 

[Ron]

I would suggest you test the aggregate using the L.A. Abrasion test method for large size aggregate (ASTM C535) and limit the loss to about 10 or 15 percent. This will imply that you have an abrasion resistant aggregate.

Don't forget that the aggregate isn't the only part of the matrix susceptible to abrasion loss. The cement paste is very susceptible and its abrasion characteristics are directly related to the compressive strength of the mix. 5000 psi might be a bit low for the application you have and the result you desire. I understand your need for low heat of hydration, but you might want to consider using a higher compressive strength for durability and control the heat of hydration in other ways (use Type II or Type IV cement).

I would also suggest you test crushed samples of the final mix using the L.A. Abrasion test to compare with the "aggregate only" results.

Good luck.

Ron