SPILLWAY CONCRETE QUALITY C30/37 or C35/45

[cdous]

I am designing a chute spillway.
I was thinking of prescribing the concrete as C30/37 but I am having second thoughts of prescribing the concrete as C35/45

The environment is cyclic wet and dry. Hence according to Eurocode it is XC4 class designation.

The design working life of the structure is 100 years.
However the member has a slab geometry, special quality control of thge concrete production will be ensured and there will be a composition demanding low permeability e.t.c

 

[hokie66]

I would opt for at least 40 MPa concrete, maybe more, for a spillway. Surface erosion can be decreased with a higher strength concrete. I would consider steel fibre concrete to increase toughness and abrasion resistance.

 

[csd72]

Personally I would go with the higher strength concrete as it is a small price to pay for a bit more durability.

The only real problem with the higher strength (as well as the small additional cost) is the additional heat created which may have shrinkage implications for a large mass of concrete.

 

[cdous]

The shrinkage is treated as temperature fall.
Replacing in Eurocode's formula fcm=38mpa for C30/37 gives a Temperature fall of -25.17C
Replacing in Eurocode's formula fcm=43mpa for C35/45 gives a Temperature fall of -25.37C
The climate study revealed an average humudity of 79.29% actulaay the lowest value in August,..I am lucky because with such humidity shrinkage is kept relative low.
Calculation wise things will not change..alot since modulus og elesticity for C30/37 is 33GPA and for C35/35 is 34GPA
Only spice and anchorage lengths are reduced with higher concrete.