How come some concrete is pitted from winter salt and some isn't?

[zonta223]

Also,to the guy who claims flyash is a better way to go....BALONEY! Flyash has been used AGAINST homeowners to STRETCH the mix(they may even cut the cement used when they add flyash)......nothing is a substitute for the proper amount of cement.
^)

I'm sorry but this statement is wrong.
Flyash is not a "stretcher" or "filler"
I work in a concrete lab making and breaking concrete of all types and all different mixes.
Flyash mix concrete (with 15 to 20% flyash) after 56 days will be harder than standard concrete as long as the correct water cement ratio is used. It is also more resistant to attack by sulfates in the soil than standard concretes. Its heat of hydration is a lot lower than standard concrete mixes which is very important when you are pouring large slabs. Standard concrete generates so much heat when curing a large slab it may crack etc.

 

[zonta223]

We make upwards of 200 sets of cylinders(Also ACI certified) in our lab in a years time, both field and lab created specimens, and I too can say that the flyash/slag/microsilica mixes far outperform those without, with a lot of economical benefits to the customer:thumbsup:

x2. We make about 1500 sets of cylinders plus thousands more ISO's every year and you are 100% correct on strengths

 

[Rock knocker]

I'm sorry but this statement is wrong.
Flyash is not a "stretcher" or "filler"
I work in a concrete lab making and breaking concrete of all types and all different mixes.
Flyash mix concrete (with 15 to 20% flyash) after 56 days will be harder than standard concrete as long as the correct water cement ratio is used. It is also more resistant to attack by sulfates in the soil than standard concretes. Its heat of hydration is a lot lower than standard concrete mixes which is very important when you are pouring large slabs. Standard concrete generates so much heat when curing a large slab it may crack etc.

Absolutely corect. I spent quite a while in a concrete class by Glacier in Seattle many years ago. The class was complete with photomicrographs and all sorts of concrete "petrology", which just so happened to be my specialty in graduate school.

Concrete with flyash is better than concrete with no flyash, as long as the flyash is added in correct proportions

 

[adirondackmtnman]

I'm sorry but this statement is wrong.
Flyash is not a "stretcher" or "filler"
I work in a concrete lab making and breaking concrete of all types and all different mixes.
Flyash mix concrete (with 15 to 20% flyash) after 56 days will be harder than standard concrete as long as the correct water cement ratio is used. It is also more resistant to attack by sulfates in the soil than standard concretes. Its heat of hydration is a lot lower than standard concrete mixes which is very important when you are pouring large slabs. Standard concrete generates so much heat when curing a large slab it may crack etc.

Couldn't have said it better myself...And besides those benefits, it's taking a rather nasty product which would otherwise end up in a landfill and encapsulating it safely in the concrete where it cannot do damage to either anyone's health or the environment...

 

[adirondackmtnman]

x2. We make about 1500 sets of cylinders plus thousands more ISO's every year and you are 100% correct on strengths

That's a lot of cylinders...I hope for your arm's sake you're vibrating those rather than having to rod them...

 

[/pine]

Absolutely corect. I spent quite a while in a concrete class by Glacier in Seattle many years ago. The class was complete with photomicrographs and all sorts of concrete "petrology", which just so happened to be my specialty in graduate school.

Concrete with flyash is better than concrete with no flyash, as long as the flyash is added in correct proportions

FWIW...

As the engineer for a marine construction co I was responsible for materials and coordinated between the client and the (sub) contractors and suppliers...in most cases the client was either the state of FL, a county or a municipality... every contract for bridge or seawall etc.(saltwater environment) projects required batch mix statements that stated there was NO flyash in the mix as per the contract specs/requirements...the only exceptions were on fresh water projects...I can't tell you how many trucks of ready mix I sent back to the plant full because they sent out batches that had fllyash...

 

[orezok]

CrazyAL .......the guy who told you order a 2"slump means well,but, he doesn't know what slope you have.I don't either,but you can pour DOWNHILL with a 4"slump very easily,unless it's more than 5"thick.
Thickness of the pour has EVERYTHING to do with pouring on a slope.
Also,crushed stone will hold better on a hill than river gravel that is rounder.
In short,every pour is different,requiring a different strategy if skilled labor isn't at hand.A skilled concrete finisher RARELY pours uphill......it's way too much WORK!
Also,to the guy who claims flyash is a better way to go....BALONEY! Flyash has been used AGAINST homeowners to STRETCH the mix(they may even cut the cement used when they add flyash)......nothing is a substitute for the proper amount of cement.
Also,the finisher IS at fault a lot, but not any more frequently than the `CEMENT Stretchers'batching it out. don-ohio ^)

I did a stadium on one of my school projects and the foreman for the concrete contractor decided to pour "downhill". This was a 600 CY pour with over 40 finishers/laborers on it. Two 30 meter pumps.

It doesn't work because the aggregate will settle to the bottom of the pour as the concrete creeps. We discovered nothing but rock pockets on the underside as the forms were stripped. many areas of completely exposed rebar. This pour was made with the State Inspector of Record objecting, but he cannot stop work, only reject it later. Stopping work would subject him to a lawsuit.

It cost the contractors bonding company over $1,000,000 after the contractor spent $500,000 and went bankrupt. You can pour downhill, but I certainly wouldn't recommend it.

 

[don45640]

Poured concrete all my life.....and you are textbook junkies that'll believe east is west and west is east. Just print it out in a manual and you guys'll gobble it up,with no experience in the real world.
FLYASH has ALWAYS been used as a STRETCHER in the real world.....that's fact,fellows! Also,air entrainment has been used as a stretcher. ANYTHING that they can rob the lil' guy that doesn't know any better,they WILL do. But on my jobs,they NEVER got to rob the householder.....concrete with flyash and PLENTY of cement is okay,but you don't NEED it,you just need the cement.
And as for pouring uphill....you are crazy if you do that and you're wearing out your men for nothing. don-ohio ^I

 

[/pine]

Poured concrete all my life.....and you are textbook junkies that'll believe east is west and west is east. Just print it out in a manual and you guys'll gobble it up,with no experience in the real world.
FLYASH has ALWAYS been used as a STRETCHER in the real world.....that's fact,fellows! Also,air entrainment has been used as a stretcher. ANYTHING that they can rob the lil' guy that doesn't know any better,they WILL do. But on my jobs,they NEVER got to rob the householder.....concrete with flyash and PLENTY of cement is okay,but you don't NEED it,you just need the cement.
And as for pouring uphill....you are crazy if you do that and you're wearing out your men for nothing. don-ohio ^I

The main reason air entrainment is to prevent freeze-thaw issues...

 

[orezok]

Poured concrete all my life.....and you are textbook junkies that'll believe east is west and west is east. Just print it out in a manual and you guys'll gobble it up,with no experience in the real world.
FLYASH has ALWAYS been used as a STRETCHER in the real world.....that's fact,fellows! Also,air entrainment has been used as a stretcher. ANYTHING that they can rob the lil' guy that doesn't know any better,they WILL do. But on my jobs,they NEVER got to rob the householder.....concrete with flyash and PLENTY of cement is okay,but you don't NEED it,you just need the cement.
And as for pouring uphill....you are crazy if you do that and you're wearing out your men for nothing. don-ohio ^I

The mix used in my stadium project had 15% flyash and it was not used as a "stretcher". All mix designs used on my public works projects have to be approved by the Engineer of Record as approved by the State Architect. Typical breaks on this stadium ran in the 5,500 to 6,000 PSI range. This was one of many projects I have done that contain over 10,000CY of concrete. I suppose you have done those also.

As to wearing out the finishers, the contractor tried to save a few bucks to make it easier on them and it cost him his business and $1,500,000 in total loss. Cut corners if you want.