Making Concrete steps for an entry?

[JKPAO]

Sealark stated the proper process! A continuous pour is best as you will not get a slurry in between pours or pumps. Forms will be needed along with a method to get the concrete thru the water without mixing in the water. If not it will turn into a loose slurry, which will fall apart easily. Any concrete will dry under water, it is a "chemical reaction" that makes it harden.
See you topside. John

 

[cool_hardware52]

The Romans discovered "Hydraulic Cement" "Fly Ash" or Pozzolana is added to create Pozzolanic Cement.

Portland cement "Hydrates" it doesn't dry like paint. This hydration reaction requires water (in the proper ratios to the Portland Cement) *AND* "Flocculation" Flocculation can only occur when the mixture is at rest. This is why the drums on concrete trucks turn as they drive to the jobsite. The agitation prevents flocculation.

Placing Portland cement concrete underwater uses a pipe or "Tremie"

http://www.ce.berkeley.edu/~paulmont/165/tremie.pdf

One fairly easy way to place concrete underwater is to use a concrete pump. A 2" "Grout" pump has a hose that is relatively reasonable to man handle into position (bring plenty of help the hose is very heavy!)

I'd consult with the local batch plant regarding the recommended mix. I'd be tempted to use faster setting cement and mix it as stiff as the pump will handle. The local RediMix supplier will also be able to coordinate a local concrete pumper.

Stair forms can be complex, Concrete is heavy (~140 / cuft) so the forms need be robust and well located before you place the concrete. Remember you will need to "strip" the forms. Give some thought as to required access etc to do so.

You should also consider finding some professional concrete finishers. It's tricky, requires a truck load of special tools, and stairs only more so.

Tobin (who has placed many 1000's of cubic yards of concrete)

 

[ScubaAl]

I've been doing concrete work since 1967, a Cement Mason from 1973 to present(retired). Send me a plane ticket :-')
University of Minnesota, Minneapolis, MN - Google Maps
Click on this link to see a set of steps I did (with much help) some years back. The entire area in the picture including the landscape areas are sitting on a post tension concrete slab that is the roof of a underground parking garage. The slope was something like 15%
Al

 

[cool_hardware52]

I've been doing concrete work since 1967, a Cement Mason from 1973 to present(retired). Send me a plane ticket :-')
University of Minnesota, Minneapolis, MN - Google Maps
Click on this link to see a set of steps I did (with much help) some years back. The entire area in the picture including the landscape areas are sitting on a post tension concrete slab that is the roof of a underground parking garage. The slope was something like 15%
Al

Very nice! Stairs are hugely labor intensive.

(but i want to see it after a rain to check for bird baths )

Tobin

 

[Akimbo]

Bit of a sidetrack here. I recently built an all concrete house, over 500 Yards³. There is a universal guarantee from concrete contractors: “It will crack, it will not burn, and nobody will steal it”.

 

[cool_hardware52]

Bit of a sidetrack here. I recently built an all concrete house, over 500 Yards³. There is a universal guarantee from concrete contractors: “It will crack, it will not burn, and nobody will steal it”.

Wow.

I like it. Nothing like a bit of thermal mass.

Tobin

 

[Akimbo]

Wow.

I like it. Nothing like a bit of thermal mass.

Tobin

Yeah, I use about a quarter of the propane my neighbors do. I consider it a lucky balance between solar gain, thermal mass, insulation, and hyper low infiltration. A/C here on the north coast is virtually unheard of so can’t compare there.

 

[ScubaAl]

Bit of a sidetrack here. I recently built an all concrete house, over 500 Yards³. There is a universal guarantee from concrete contractors: “It will crack, it will not burn, and nobody will steal it”.

I tell people the same thing all the time, with a huge smile of course.
Tobin, bird baths? well if it gets deep enough it will run:-') Every some many steps the is a trench drain install. This set had 110 risers, at the top 13ft wide, 27ft wide at the bottom. Poured the walls first then steps starting at the top. Something that made this more difficult, being its all on a post tension slab we could not drill or anchor into it. Some areas were marked out when we did the walls that we could drill into. When the steps started these areas were no longer available. I always like the challenge figuring how to build something. Like an architect once told me when I asked how he expected us to do what he had drawn, "I draw it, you build it" well okay then.

 

[cool_hardware52]

This set had 110 risers, at the top 13ft wide, 27ft wide at the bottom. Poured the walls first then steps starting at the top. Something that made this more difficult, being its all on a post tension slab we could not drill or anchor into it. Some areas were marked out when we did the walls that we could drill into. When the steps started these areas were no longer available.

Pretty good trick to hold the forms in place with duct tape and bubble gum.

Bad form to rotohammer through a post tension tendon.......

Tobin

 

[Iknee]

The biggest challenge you are going to have isn't placing the concrete under water, it will be the wave action in the surf zone. As mentioned in the other replies, ordinary concrete can be placed under water.

For a comfort margin, you can use a welan gum based Anti-Washout Admixture (AWA) to minimize washout during placement. Your local ready mix concrete supplier could get you some to add to the truck.

Precast would definitely be easier. Either way, make sure the concrete meets the durability requirements for the exposure condition (minimum .40 w/c, use of SCM). The American Concrete Institute produces specifications and guidelines you can reference. ACI 318 gives exposure recommendations, but ACI 357 is the "Guide for the Design and Construction of Fixed Offshore Concrete Structures".

Call your local ready mix concrete's QC department and ask for them to make you a copy, and give you additional help. Or you can PM me and I can send you a copy and give you advice for mixing it yourself.