Urgent - Layer Wise Concreting

I'd say the maximum time allowed between placing the second layer of concrete would be unlimited. You might want to etch, or otherwise prepare the "old" surface proir to placing a second layer if it's been awhile since the first layer was poured.

Now, the minimum time would be much shorter, but that's not what you asked.

Agree. If rebar is being used, have some covered by the first layer and extend upward, exposed, so it will grab onto the next layer of concrete to help bind the two layers together.

The concrete needed should be homogeneous and is a single pour as it is for turbine deck. Hence second layer should be placed immediatelyafter first layer.

Hence what is the maximum time before which second layer must be poured in order to allow a homogeneous mix.

I think it should be before final setting time that second layer should be poured.

Do you agree?

Have you placed an urgent telephone call to the concrete supplier?

A: Yes, but I did not like the answer he gave me. I hope you give me the answer that I am looking for. Then when failure occurs, it is still not my fault.

B: No, why? Would that be a good idea?

Be nice if the guest mentioned what they are up to. Such as a motor foundation, building column or simply laying down a cover coat (screed layer).

If you have a cold joint in your concrete work you can always apply a "concrete bonding agent" to the exposed surface prior to placing the new concrete to form a monolithic structural member. Make sure the exposed cold surface is roughened-up and thoroughly clean of debris and fines.....power pressure washing w/ clean water or high pressure air blasting works fine.

Contact an appropriate chemical manufacturer of concrete products for details and technical advice. Also check out Sweet's Catalog online for a starting point.

If you are trying to avoid a cold joint then you must place the second layer before the initial set of the lower layer. This is usually about 2 to 3 hours after the concrete has been mixed.

The actual initial set time depends on many factors and can be extended with the use of retarding admixtures.

Thanks a lot. That will solve the issue.

Considering where am working now, only 90 minutes to prevent cold joint.

aCres

Guest,

You have some points to consider concerning your question! More important than the "Time" between lifts is; what you do to prepare for the next lift and what operations are continued while you wait.

The comment about a bonding agent is close , but No Cigar. PM me and I'll send you photographs of what it looks like if you don't do it right.

You mean that if one buys your angel dust the next pour can be done at anytime? As in next week? Or next month?

I knew Labs/Retriever's were very smart dogs. Glad he gave you the correct information. By the way our clients jokingly refer to it "Miracle Piss" or "Whiffle Dust" not angel.

Yes, next month or next year is OK, [providing you keep your ears open and mouth shut], but projects we are involved with typically trigger faster than that. A project having 18" poured, pumped or shot walls that is then taken hydraulic for a leak check will show you cold joints in about 1 hour if you've screwed them up!