Cold weather placements 2

[Dryhands]

I'm a newly certified concrete tech and have been certified in soils for a little bit. Soils was easy to tell what was acceptable because moisture was the only thing I had to really watch out for. I trained for a while under some good techs and learned the general acceptability range for concrete, I can tell whats good enough. I know they put a bunch of funky stuff in the concrete to keep it viable in the colder weather (under 32) but does this affect me at all? Basically I'm wondering wether I should be more or less lenient, allow the batch plant todo there thing and trust in Jesus, keep them in normal perameters or be stricter? Also is there anyway the added chemicals could specially influence any of the tests? I just test the stuff so I guess I don't really need to know but I was also curious what the cold weather chemicals they add are if anyone knows

 

[Ron]

From reading your post, I can see that you take your work seriously and it's always refreshing to see someone who is dedicated to what they do and always wants to learn more. Good for you.

As for concrete, it is a relatively complicated material in some respects and very simple in others. Chemically, it is very complex. While we are still learning about the complex chemisty of cement and concrete, we know enough about the basics of cement and concrete technology that we can predict its performance based on initial characteristics and some basic testing.

As a technician, your job is to observe, test and report....plain and simple. Your task is not to troubleshoot the mix or modify the mix in any way. However, the accuracy of your observations, sampling, testing and reporting will go a long way toward helping others who have the responsibility to correct concrete problems.

The concrete is typically produced by a ready-mix supplier. That supplier has the responsibility to deliver a concrete mix to the jobsite that is within the requirements of the specification. When it arrives to the jobsite, it should not be changed in any way (such as adding water to the mix) except by the ready-mix supplier's quality control person. That is not you, that is not the concrete placement foreman, that is not the project superintendent or anyone else except a quality control employee of the ready-mix supplier. If anyone else changes the mix before it is placed, that person then takes on the responsibility for the performance of that mix.

In order to further understand concrete placement in cold weather, I suggest you obtain and read a copy of ACI 306R "Guide to Cold Weather Concreting". The National Ready Mix Concrete Association (NRMCA)has a guide for cold weather concreting that has some good information, but is certainly not complete in its treatment of the subject. I am attaching a copy of the NRMCA document for your use. I cannot post a copy of ACI 306R as it is copyright protected and sold by ACI.

An excellent book to give you a thorough background in concrete technology is "Properties of Concrete" by A.M. Neville. Any edition will help, but the latest are the 4th and 5th editions.

Good luck and keep knowing that your task is important. Be well informed and learn as much as you can.

 

[Dryhands]

Thanks for the reference material, I'll at least find a copy of the aci standard somewhere. My boss told me he'd kill me if I sign a water ticket or anything of that nature. I believe there's an older addition Portland cement book in my lab floating around, I'll take a look at that. I looked at it a couple months ago and it all went over my head but I think it will be easier to understand now. Thanks again for pointing me in the right direction

 

[Ron]

It also sounds like your lab does not have proper reference material. Ask your supervisor to purchase appropriate references for all of you to use. It will protect your company's liability in the event that they are ever brought into a lawsuit....which is a common occurrence. If it comes out that you don't have adequate equipment, proper references or good training, your company will be nailed to the wall!

 

[bb29510]

when it comes to testing anything, just write the number down. do the test, write the results and think about whats for lunch, you are just a data collector, let the engineers worry about theater its too cold to pour.

 

[Ron]

bb29510...WRONG!

A technician is not just a data collector. They are your eyes on a jobsite and if you have brain in your head you'll learn to listen to them. They can offer insight and experience that you'll probably never get because of your elitist attitude.

Your comment is a disservice to technicians who are out there protecting your a$$ on a daily basis.

 

[BigH]

Agree wholeheartedly with Ron - and to add another point - do testing, write the results - CRAP - you need to make sure the results make sense. Something I saw no more than 90 minutes ago - my lab gal came in and showed me some test results by the contractor's lab (Contractor is responsible for QC) - the bulk density of a reddish brown clayey silty sand with some gravel was 3.662 Mg/cc - something is wrong here and the lab technician and the checker should have found it.

 

[Ron]

Hmmm.....math error and order of magnitude eh, BigH?!

I agree with you that technicians need to be able to spot test anomalies and know when they have good data or crap.