Poor design led to I-35W bridge collapse?

Status reports are part of maintenance.

/BAH

Spending does not necessarily mean doing the real work. That's the problem.

/BAH

Where are these holes made? On the top or from the bottom? Do they fill them in after taking the sample?

I always thought that, the higher the tech, the more it costs. Does the radar device make a picture like an MRI does?

Oh, not water but other stuff. damned news. This particular concrete was supposed to waterproof the tunnels. And the word slurry is a common noun used in the news reports. I don't know what that is either.

I must be misremembering something my Dad said. I thought he'ld told me that too much water does not let it cure to hardness. It eventually falls apart.

That's true about all the news these days.

Liberals, honey. City slickers who believe that fairy tales are true ;-).

That's why I keep wondering why the state chemist wasn't doing his/her job. I would have assumed that samples of the cement were taken before pouring.

Any bodies? ;-) I just read a bio about Daley, the father. I knew Chicago was bad but not that bad.

Poor baby, can't bid. There are ways around that. I would have given him the task of fixing his mess-- one square foot at a time.

/BAH

Top down. Yes, they are filled in.

I'm sure that someone scratching deeply can find one that doesn't store images but most do. Perhaps not quite like an MRI though.

Concrete is another of those things that behaves differently whenever one gets off the ideal blend with any of the components. As with everything else, a little too much plays into a little determent. When you're talking about too much water then some too much isn't the same as much too much. The two paragraphs above are saying the same thing, you're not misremembering.

Today's news reporters are making themselves part of what they're reporting about.

They are what they eat.

Pre-pour "slump testing" is all there is. There's no test available to determine whether or not the blend is correct or what the cured strength of the concrete is going to be. Post cure destructive testing tells all.

Who knows. Helen Brach is still missing. But Lake Michigan is h-u-g-e and easily accessible. I think you're more apt to find bodies in the deep parts than under roads.

You maybe read Royko's biography of Daley?

Richard M is a wimp and a wuss. Richard J was a power to be held in awe. To this day the one thing that visitors to Chicago all comment on is how clean the place is, one of the old man's legacies.

Richard J has been rehabilitated in the years since his death.

It is only a couple of years more till Richard M is mayor for as long a period as his dad was. I think he's been a lot better in the job than those few who were in that office between Richard M and his dad.

Even if it were all spent on doing the real work the amount might be inadequate.

They should take sewing lessons. A breach becomes a weak point. Doesn't this happen with bridges?

hmm...I'm trying to picture in my head how a fault can be detected if slices of cross sections of the bridge can't be taken. I guess I'm stumbling over stuff I didn't know I didn't know.

OK. Good. At least some of my memory cells are functioning :-)

Yea, I know. What I try to do now is negate what they are saying and then try to figure out why there is a need to lie. I never did think of an answer when Clinton moved his lips.

Which is all produced by magicians in the back room of the grocery store.

JMF's cousin is a chemist. His job is to test the stuff before it leaves the cement plant. Each job has a different chemical construction requirement. I had assumed that, if this can be done at the cement plant, a similar chemistry analysis can be done with samples taken at the pour site. I had assumed that part of the ongoing inspection activity would involve this kind of chemist. But, alas, this would be common sense. Silly me ;-).

Nah. The Lake is too frisky to keep bodies on its bottom.

I can't remember the author and I don't know where I put the book. It was a newspaper guy who had covered Daley's administration.

Is he really? Then who runs him?

I've been reading about the political machines. They did a better job training politicians than what we have now. I simply can't think of a way to instill a checks and balances system in the machines because the successful ones are based on a personality; this is also the cause of corruption (there's no turnover to keep people from becoming entrenched in their little empires they built).

/BAH

It doesn't seem to be a problem. A nice round hole distributes the stresses evenly, and these days they avoid the rebar.

Horizontal fractures seem to me to be rare.

They have a lab at the plant, not reasonable to have in the field to intercept and test every load that arrives and pass it before they pour their load and head back for another. If the state actually wanted to I'm sure they could put an observer (liaison) in the chem lab where JMF's cousin works and just watch over the guy's shoulder when batches destined to their jobs are being checked. There's usually no need to get into depth with this issue. Most providers are honest.

Well weighted down makes excellent fish food. They don't last very long down there, and I don't think bones float real well.

Royko.

That's not a given. Little pockets of corruption are prevalent. See the web site for the "Better Government Association" when you're next at the library.

It was an upward mobility issue for machines like Tammany Hall in its heyday. Today's politicians are lacking for nothing when they enter the arena, leaving little to lose if they don't make it (with help) in politics. You just can't keep a guy who has other options in line as you can with a man who has only "this one shot" at being well off.

Glass ceilings also lead to corruption. An individual refused continuing ascent often branches out in other ways to make up for what he thinks he's entitled to but isn't getting.

Part of the problem is that the post WW2 generations have been raised to think that upward mobility is another of so many absurd entitlements. Today just about every mailroom kid thinks they'll be running the company some day. The classical "American Dream" doesn't seem to count for anything any more.

This is a universal problem, not limited to politics.

Why would any kind of chemical analysis done at the pour site give any different results from that done at the batch plant?

The point, in this branch of the thread was that Corrosion of Steel encased in Concrete is a concern such that simply replacing steel bridges with concrete bridges does not remove the requirement of maintenance, nor automatically provide that a concrete bridge will last longer than steel.

The fact that the I35W bridge collapsed, appears to be a compelling example that spending has not equaled real work, or at least expected results. None the less, corrosion of steel in concrete structures is a known concern.

...

I used to work for a Concrete Ready-mix producer in Minnesota. This is how it's done here. It can be different in every state.

These are not just holes, they are Cores. They are used to verify the distribution of aggregates and other additives (steel or polypropylene fibers) within the structure of the placed concrete. These core cylinders are then structurally tested by breaking them in a press at a 3rd party lab. (Not the Concrete Producers, nor the Contractors)

Concrete Producers also cast test cylinders on site with a frequency up to every truck, or every few hours depending on the size of the pour. These cylinders are kept by the Concrete Producer in a climate controlled lab for break testing after 28 days. Nearly all concrete mixes are specified to reach their designed strength after no more than 28 days. Environmental or manufacturing anomalies can cause the specified strength to not be met within the 28 days. Concrete continues to cure well past 28 days and often the final, stable strength will be much higher than the 28 day specification.

State, Federal, and Airport pours require a STATE INSPECTOR at the plant producing the material, as well as at the job site. State, Federal, Airport, and some contractors require manufacturing Batch Weights to be printed on the delivery tickets. Concrete is mixed in batches by weight and volume. The batch weights computed based on the mix design and the qty of product to be produced by the Batch Plant computer system. This system is then responsible for printing the weights on the delivery tickets.

This is so the Inspector at the job site can ensure the proper mix design for the particular placement is in the truck that just arrived. Batch weights for all product run through the concrete plant are printed on to a paper report as well as stored in a file that is sent for storage on a central server should any review be necessary. This information is used by engineers at the concrete producer when they break cylinders so they can validate mix design with actual performance.

Scales at Concrete Plants in Minnesota are required to be certified every 12 months.

...

Slurry is a term used in Ready-Mix operations to define the "wash water" used in rinsing out the plant or the trucks. Ready-Mix producers are being forced to be more environmentally friendly. In some locations they are required to "reclaim" their wash water. The trucks need to be rinsed out when they get back to the plant, or the plant itself may need to be washed out. Once a truck unloads at a job site, the driver will dump water into the drum to keep any remaining concrete from hardening to the interior of the drum (assuming all concrete was off loaded or any remaining will not be re-used) When the trucks arrive back at the plant the discharge this water/cement/ rock/sand mix into recovery system. This recovery system will extract the aggregate, sand, and cement back into the component parts.

Currently the best they can do to extract the cement is to suspend it in the water, producing a "slurry" mix. In some applications (quite few in fact for the producer I worked at due to huge variability in the actual composition of the slurry water) this slurry water can be used as the water component of the concrete mix, and due to its cement content, dry cement added can be reduced. For this to work though, the content of the slurry must be closely monitored as its makeup can change at any time as it flows.

Water increases the heat of the curing concrete as it gives the cement more active elements two work with. The problem is that the water is taking up space in the matrix thus while the concrete may appear to cure faster it actually ends up curing less dense, and thus weaker. The strength of concrete comes from the mechanical bonds between the aggregates and the cements. The right amount of water achieves the best. Too much water and you might as well have not added enough.

Note there are admixtures commonly that cause the concrete to act like a high water content but actually has low water content. Say the spec calls for a 6" slump (when using a slump cone filled to the top and tipped over and lifted, the concrete will drop 6" or slump) yet a high strength at 28 days, a 4" slump mix will be used and then an admixture will be added that causes the concrete to act like a 6" slump. These admixtures bond to the cement and restrict curing. With standard dosages, you get about 1.5 hours to get the concrete off the truck and placed before it suddenly becomes 4" slump concrete.

These admixtures are quite expensive.

That is a very good question. I'm sure we won't hear about it in the national news, but I'd like to hear how the cylinder break tests went for those test cylinders. My guess is that either they "forgot" to make test cylinders for those sections, or they "lost" them.

When that happens, it almost always will require a core to be drilled to allow for testing.

Less chemical analysis more physical analysis.

Things done at the plant:

Moisture tests - Verify the moisture content of the aggregates as these numbers are plugged into the batch computer for it to optimize the water content calculations

Gradation Tests - Verify the size and weight of the aggregates using screens and scales.

Slump Tests - Verify batch plant calculated slump is achieved.

Flow tests - Using graduated beakers, verify that if the computer says it just put 300ml of fluid out the valve, that that is really what came out.

Things done at the job site:

Slump Tests

Create Test Cylinders

Verify Batch Weights on Delivery Tickets

Verify Time in truck. - Most states have a specified amount of time concrete is allowed to have been discharged from the plant to being placed. Say if you are pouring a 300cy pad with a pump truck and you have 4 trucks on site waiting to unload. If the pump breaks down, the last truck in line may not get the concrete off in time. In which case the inspector will reject the load.

Producers then will try to use that concrete elsewhere. (Say if it's

5000psi spec concrete for a state load, but it's getting old, it'll work fine in a footing for a house or garage that normally only specifies a 3500 psi concrete. This because if the concrete is old, they will need to add water to keep it flowing which will bring down it's final strength.

Nice post! Thanks

Brian Whatcott Altus OK

Lots of things can happen on the way to the forum.

/BAH

Thank you for taking this time to teach me!

I had no idea cement can be cored. What kind of drill do you need? Does it need diamond edging?

ARe the forms for those cylinders laying down or are they upright? Does it make a difference which way they lie?

Oh!!!!

Now I understand. It appears that everything having to do with the Big Dig was put into "hurry it up" mode. So they^WThey used things that dried fast. The only company to get its hand slapped (so far) in the tunnel ceiling failures is the company that provided the glue to stick the cement slabs to the ceiling. It was a fast drying epoxy and the company has stated that they sent memoes warning about using the quick-drying materials.

The same thing must have been done with the cement that was (according to the news) supposed to make the various tunnels water proof.

OK. I may have leapt to the wrong conclusion but now some things are making sense to me. THANK YOU VERY MUCH!!!

I've just tripped over more stuff that I didn't know I didn't know. Kewl! Unfortunately, I don't not-know enough to ask questions.

I have a hypothesis. The brother-in-law who had this job never showed up for work. That seems to be SOP in this state.

And I'm sure we won't hear about it in the local news.

MIT kept sending students to observe the construction over the

15-20 years it was getting done. Would these "newbies" know enough to look for them?...and look at them?

Does every concrete piece of a project have these sample cores stored somewhere in the world in perpetuity?

/BAH

I guess you missed this when I wrote about it a few posts back.

A core drill with an abrasive edge.

Most do though there are those with carbide. One of the partnered businesses I started refurbishes spent core drills by brazing new diamond segments to the spent drill. We currently refurbish from 2 through

24 inch units.

A favorite method of examining rock remanent magnetism, in connection with geomagnetic reversal research, is to use a one inch or two inch core sampler, having marked the compass orientation and slope of the sample. The read out takes a sensitive magnetometer, and sometimes a bakeout.

Brian Whatcott Altus OK

...

Just to throw out a common jab that folks in the ready-mix industry do, cement isn't cored, concrete is cored. Cement is a component of concrete. Cement is a powder, Concrete gets hard.

To get any life out of anything used to cut concrete, they almost always have a diamond impregnated cutting edge. Expansion joints in concrete driveways are often cut with diamond edged saw blades. Both saws and drills almost always use water as a coolant during cutting.

Test cylinders are a round cylindrical shape and the manner in which the material is collected and tested is specified by the ASTM. Here is a guide on how this is done from the National Ready-Mix Concrete Association.

...

Test cylinders are almost aways destroyed in testing. Thus they don't hang around. The testing that will take place is dictated by the Contractor, Architect, Engineer, and often Concrete Producer.

The Contractor et al, will want them to validate the designed strength is met allowing them to avoid taking core samples. The Concrete Producer will make the samples if they are trying to validate a mix design or design change.

Note that in nearly every case, when discussing the "strength" of concrete, we are discussing the "compressive" strength of the material. Basically how well it resists crushing.

If there are any cylinders still around after 28 days, it is because one cylinder was found to have not met the spec after 28 days. Thus the engineering group has decided to test again after another 28 days to verify that the engineered strength will eventually be met. This can happen on a pour if environmental, or issues at the plant cause a slight mix change that isn't noted. Baring any significant problem, the concrete will eventually cure.

That's not true. Expansion joints are poured in with a compressible material filling the joint. What you're talking about is scoring that's put in after the concrete is poured and partly set. The score lines have the purpose of giving future cracking someplace specific to go.

Yes.

snip

...

You are correct, I used an incorrect term. The joints cut into the concrete are called "control joints" and are used to promote cracking in a specific location. Expansion joints are as you stated, gaps filled with a compressible material. Such joints are necessary wherever a slab comes in contact with another object (another slab, a wall, a curb) otherwise the expansion of the slab when heated could push against things and either move them, or crack the concrete.