Concreting on sloping surface 1

[19652022]

Hi All,
I have to cast 100 mm thick concrete slab on a sloping surface with 30%(10 horizontal,3 vertical) slope.The concrete must be very dense and waterproof. If vibration is used all concrete will slide down the slope. So how can I then compact the concrete? What is the solution to this problem?

 

[cvg]

use very low slump or try shotcrete

 

[BigH]

Won't be able to vibrate - at least using poker. What we did in China was to use a wooden 2by4 and tap tap tap tap, etc. Then trowel well. Ensure that laitance is removed. As cvg says - use low slump (e.g., 25mm) concrete. Might want to check out admixture so concrete is non-shrink - also might want to use fibre reinforced to minimize potential for cracking. Ensure that you follow good practice to prevent plastic cracking - use fog spray if hot low humid and windy day.

 

[JedClampett]

We build a lot of hopper bottom reservoirs. The side slopes are anywhere from 1 vertical to 1.5 horizontal to 1 vertical to 3 horizontal. We require the contractor to pour from the bottom up. To do this they need a rotating screed (about 15 to 20 ft. wide) that they drag up the slope to screed the concrete. Pouring from the bottom up assures the best quality concrete in this situation since gravity is working with you in compacting the concrete. We typically allow a two to four inch slump.
I'll ask some of our inspectors (they've went home already today) how the vibration is accomplished.

 

[locksman]

I don't know exactly what the application of the slab is for but I have seen concrete bags (or mats) used to protect slopes. Only two companies I know of make them. It seems many people are unaware of them. This may not be of any help but it may be useful in future projects.

 

[dicksewerrat]

Gabions work well. Wire baskets filled with rocks. make them any thickness. Hand placed concrete blocks and filled with dirt and wildflower seed is nice too.