Concrete – Follow up to the discussion on Damo’s Blog
Richard, All,
This blog is in response to a conversation on Damo’s last feed.
Here are some photos as requested. I must add that although this abutment will be black jacked (bitumen cover) and buried it was intended to look exactly like the finished bridge…we have some work to do!
The kicker should simply look like a line joint
The wing wall has had to be built up. This will not have the durability it should. If you look closely you can see aggregate viable on the top face.
Staining, we’re not sure why…has anyone had anything similar? I am conducting trails in a couple of weeks to try out different formwork materials
In other news, we hit an obstruction in the river and had to bring in a spud barge with 45tn machine. It proved to be a great spectator sport but not much work was done on site whilst it was here.
Holdfast Training Services Trial Blog 
We had the same issue with staining in Perth. I thought it may have been some of the additives but it had not occurred in other similar mixes. To be honest the issue came pretty low on my radar as the columns were being clad and the strength, if I remember correctly was a ridiculous 80MPa trial. Potentially unclean forms but more likely something to do with curing, whether in the for work, or wrapped in polythene.
Olly are you using bog standard reinforcement steel. I showed someone here and they wondered if your steel might be galvanised or stainless? Apparently that can sometimes cause the greeny blue stains you’ve got.
Thanks guys,
The rebar is bog standard steel and the forms were brand new on this pore. They were struct 24hrs after the pore. I can only assume the staining is a result of the de-bonding agent or an additive.
I’m running a PT duct grouting trail next week. The scope of the trail has been increased to facilitate various forms and de-bonding agents. If that doesn’t solve the issue then we know the problems is with the mix and not how we are handling it.
Olly
In quite a few previous attachments there are always trials with different materials and formwork to get an acceptable finish. Has no one suggested that or is it not in the contract/specs?
NJP
Already on it.
The spec requires us to conduct a tendon grout trail and a concrete finish trail only. It has been decided that due to some concert problems shown here and a couple of things that have happened since we will expand the trail to also look at three different plywood formers with two different debonding agents. We are also testing the accuracy of the duct fixing through a curved section and the fixing of the PT jacking trumpet. Another trail will allow us to fully construct two PT end blisters with all of the rebar. The placing of the helical link through all of the mats is a nightmare.
I have picked up these tasks and have finalised the designs today, we should be running the first in a week or so and its attracted quite a bit of interest so stand by for me being RTU’d and requiring a new placement 🙂