The roadway maintenance thread

[bykfixer]

There's a lot of that in the gov't contract world as well IP. But I have found that most of the workers have good intentions yet do not at times understand the little details spelled out in our library of specs and standards. Heck, it's not unusual for us inspectors to discover an obscure spec was changed 3 years ago through an email from one office dweller to another and we built things by the old spec…… then an expert from the Taj Mahal whose sole purpose is to protect his or her job and suddenly it's like Pearl Harbor all over again…… over something trivial more times than not.

We refer to those changes as "only available in the mind reader manual". I get a kick out of reminding those types how a federal spec over rides their little ideas. Oh, they hate that.

In the meantime folks will get used to our little round about or they won't. We have another saying; "can't see it from my house".

 

[scout24]

All this talk of roundabouts... I get to encounter this one (Three plus a cloverleaf) often enough to have it stick in my memory to get a pic and post. I think there should have been an award given somewhere here... Thoughts, Mr. Fixer?

 

[knucklegary]

Two roundabouts on Williams appears overkill. Is that a high traffic area?

..bet it's fun on a bike?

 

[scout24]

KG- I can drag a footpeg on my Goldwing as long as Mrs. Scout isn't with me.The fun is coming off 81 south, using all 3 roundabouts, going back to the second one, and then taking the big looping on ramp for 81 north. Again, without Mrs. Scout. "Why the heck did we just do that?" "Because we could!"

Edit- Not particularly high traffic. Not sure what the thinking was.

 

[bykfixer]

That triple round about was perhaps brought to you by the same folks who brought us brail at drive up ATM's?

 

[knucklegary]

Scout, lol.. I thought the same, it's like a moto course. Too bad they didn't leave one circle dirt for riders (-;

 

[bykfixer]

The latest project is repair parts of bridges over a highway built in the late 1960's. It's called substructure repair as the vertical and horizontal items the bridge deck sets on. The part underway at this point involves busting off bad concrete, attaching what are called "sacrificial" anodes to the steel rebars and spraying a lightweight concrete over the area where concrete was removed.

Now ordinarily the decay of concrete comes from weather. As wind and rain hit these areas year after year it can be like sand paper on the surface. And the biggest problem with bridges is when the steel reenforcement rusts it expands and breaks up the concrete. Often that comes from salty water that comes from melted snow reaching the steel. Maintenance crews spread salt and sand over snow that later melts so you end up with salt water.

The client I'm working for has hired a contractor who fixes bridges near the ocean or at the ocean from Florida to Delaware. Some hard working fellows who grew up in coal country where you either worked at the mine or you work out of town construction. These guys are thin as twigs but strong as an ox, and smile very easily. They enjoy what they do. So for this inspector it's been fun to watch these guys do their thing.

One issue that keeps popping up is the rebar is too close to the surface of the concrete. The years of wind and rain caused rebars to become exposed and begin to rust. I won't critisize the folks who built these bridges in the 1960's but will say the inspectors sure did miss a lot of things that cost taxpayers a bunch of money that should not be needed to be spent.

Here's one that has steel buried about 1/8" instead of at least 2".
That led to rust getting deep into the rebars.

An area after bad concrete was removed.
Steel is cleaned and then an anode installed.

The anode looks like a Twinkee.
It is attached to the bars at specific distances, a resistance is read and if it's ohm number is 1.0 or less the anode is then the item that will decay instead of the steel rebar. The technology says they'll protect the steel at least 20 years.

After that concrete is sprayed over the area to become a patch.

 

[Poppy]

The latest project is repair parts of bridges over a highway built in the late 1960's. It's called substructure repair as the vertical and horizontal items the bridge deck sets on. The part underway at this point involves busting off bad concrete, attaching what are called "sacrificial" anodes to the steel rebars and spraying a lightweight concrete over the area where concrete was removed.

<SNIP>

Hmmmm, that was interesting

 

[KITROBASKIN]

Evaporative coolers can have sacrificial anodes. I've seen them degrade to particles with the bad mineral salt water at one location.

Maybe fixer can elaborate on the coated rebar that is often used in this kind of construction these days.

 

[PhotonWrangler]

I remember seeing an episode of Dirty Jobs where they were replacing sacrificial anodes inside of a structure. I think they were zinc and they were about the size of a brick. They lasted maybe 5-10 years before they had to be replaced.

 

[BVH]

I remember the old Clayton automotive dynamometer had a sacrificial Anode, to be changed every year or two depending on usage.

 

[Poppy]

https://youtu.be/pxODVsgHRfc

Hot water heater anode replacement

 

[bykfixer]

These are zinc on the inside PW. The outter coating is a weather resistant poly something or other. The manufacturer says they'll last 20 years in the environment they are being installed in. The manufacturer in this case used to use round disks but decided to go with a shape like a twinkie since it can fit behind steel easier in the case like where we are that steel is too close to the surface. They require the finished product to appear like the existing surrounding area so to give the steel proper coverage would require buldging patches.

Here's two patches
The client does not allow the use of trowels to finish the patch smooth. Using a trowel wicks the water that makes the concrete a semi-solid at first to the surface. So when water molecules wick to the surface they leave microscopic conduits that allows the salt to reach the steel. Lab tests over the years have shown that just scraping off the extra with a flat blade actually provides a more weather resistant surface than smoothing it with a trowel. After patches have cured 28 days the contractor will spray a heated epoxy over the entire "pier", which is the legs called columns and the top area called the "cap".


The steel in the bridges being repaired is called "black steel" as it's an uncoated, non treated version of steel used back in the 1960's. In the 90's various DOT's tried epoxy coated but found for various reasons it was decided to use stainless these days instead. I'm not a bridge guy so I'm not familiar exactly why they got away from epoxy coated. Years ago I tested the concrete used so I saw a lot of green (epoxy coating) steel get covered with concrete. Not long ago I was assigned environmental monitor duties around some bridges that were using stainless. I asked "no more epoxy coated steel?" and the answer was "not anymore". They were using black steel in the walls that line both sides of the bridges and stainless in the riding surfaces since around 2010 in my state.

Down the road a few miles there are some bridges that will be patched with experimental concrete that does not contain rust inhibitor additives along with sacrificial anodes and cathodes being used along with a zinc rich coating. They'll be used to provide data comparing various alloys on components that have decayed much worse than the ones being repaired now. I've been tapped to go elsewhere by then so the up and comer I requested will get to put that on his resume' when it's completed. We did some inspections of experimental stuff last summer and he really took to the travelling down a road in a decade and seeing whether it worked or not.

 

[PhotonWrangler]

Interesting, bykfixer - thanks. I've always wondered why rebar looked green and now I know. And I had no idea that the trowel would leave microscopic conduits for ingress. Fascinating.

 

[bykfixer]

If you've ever seen a frumpy old bent up guy finishing concrete you'd likely seen him rub, and rub, and rub the surface with a trowel to get what's called "bleed water" to the top as a way to get a nice, smooth finish. In the 80's concrete mixes began being produced in a way that limits how much of that bleed water can be brought to the surface since it had been discovered in the 1970's that bringing the bleed water to the top left tiny pores that allow salt water to reach the steel in the conctete. So the art of "blessing" the concrete was born. These days you see folks dunk a paint brush into a bucket of water and sling it onto the concrete surface like the Pope does when he blesses stuff. Bridge building contractors "fog" the surface to provide a uniform amount of water in a very limited volume. Another machine passes over the surface to rub the surface once. 28 days later a grinder machine cuts grooves in the concrete. It's gotten very scientific but the results are bridges that last longer.

Years ago I attended a seminar held by a guy with a doctorate in concrete production. My initial thought was "it's gravel, sand, cement and water, how complicated can that be?"…… Now in our certification classes we have a 22 chapter manual that we are tested from. Tested from 3 of the chapters. One year I read the manual cover to cover in small chunks while sitting on the toilet. About half way through I realized how somebody could spend 10 years in college learning about mixing gravel, sand, cement and water.

Some of the places needing patches have not been exposed to salt water, nor is the steel too close to the surface. In 7 out of 8 "caps" on the underside the concrete is just rotten for no apparent reason. Last night it dawned on me why. Again it's a workmanship issue. But again I will say the inspector should have caught it. You see, when concrete is poured into forms it can be fluffy. Fluffy concrete means it's not as dense as it could be, therefore not as strong. The solution is vibrating rods poked into the concrete to consolidate it. One drops the vibrating stick into the concrete briefly, like a second or two then lifts it out and moves it over a half foot or so. If left in the concrete too long the components of a well mixed batch of concrete begin to separate. The big stuff goes one way and the little stuff another. It's called segregation.

Now if it was under consolidated, one sees large pours called honeycomb when the forms are removed. Honey comb is a no no to most inspectors. And to the guy who has to go back and correct honeycomb areas it's also a no no. So the guy with the vibrator leaves it in the concrete a little longer to make sure there's no honeycomb. Sometimes they'll leave the vibrating tool in an area for 6, 8, 10 seconds. And when the tool is touching the form it also resonates over a wider area causing segregation. Unseen segregation unfortunately since when forms are removed it looks nice and smooth. Trouble is 20 years later frisbee sized hunks of concrete begin falling off the cap. Most inpectors I've worked with over the years do not recognize the issue. No honeycomb to them is the goal. Yet if done correctly a little bit of honeycomb is not unusual. Fist size here and there is better than segregated concrete.

I cut my teeth in maintenance so my default is what can go wrong in 5-10-20 years. The design is for bridges to last 100 years. So the work taking place on these 52 year old structures is not due to a poor design or poor materials. What I teach my trainees to watch for won't be known for decades. Probably after they have retired.

 

[KITROBASKIN]

"The design is for bridges to last 100 years"
And yet, ~1800 years ago:

Built in Rome in the 2nd century AD, the Pantheon is a massive concrete building capped by an impressive 142-foot-high dome—the largest in the ancient world. ... Many scientists have pointed to the practice of including volcanic ash in the concrete mix...

 

[Chauncey Gardiner]

"The design is for bridges to last 100 years"
And yet, ~1800 years ago:

Built in Rome in the 2nd century AD, the Pantheon is a massive concrete building capped by an impressive 142-foot-high dome—the largest in the ancient world. ... Many scientists have pointed to the practice of including volcanic ash in the concrete mix...

Affordable price

longevity

Pick one.

 

[bykfixer]

I wasn't there but if history is recorded correctly the Caesar did not have bridges built to be cost concious by the low bidder. Perhaps that plays a role in longevity?


The bridges I'm always astounded by are those rope and stick bridges that cross canyons.
But these days you can even buy those at Amazon……

 

[idleprocess]

"The design is for bridges to last 100 years"
And yet, ~1800 years ago:

Built in Rome in the 2nd century AD, the Pantheon is a massive concrete building capped by an impressive 142-foot-high dome—the largest in the ancient world. ... Many scientists have pointed to the practice of including volcanic ash in the concrete mix...

Affordable price

longevity

Pick one.

I wasn't there but if history is recorded correctly the Caesar did not have bridges built to be cost concious by the low bidder. Perhaps that plays a role in longevity?


The bridges I'm always astounded by are those rope and stick bridges that cross canyons.
But these days you can even buy those at Amazon……

I recall that roadbuilding was the traditional peacetime activity of Roman legions, who were kept busy so as to reduce the risk they presented to the state.

Also, in addition to the economic benefits that the roads brought, they were of prime military value ergo cost is less of a concern.

 

[bykfixer]

Funny you mention military uses. A long time ago I was inspecting what we called an erector set bridge in the middle of nowhere. The kind you snap your fingers and you've crossed it. Now the front pages of the plans have interesting stuff like how many axles are theoretically going to cross it per year and projected numbers in 50 years (and in some cases 100). The erector set bridge had a "G" rating. I asked my lead inspector what the G means. He told me the higher the G rating the heavier the military vehicles can be and even though it is nothing more than a thin line on a map this road is part of a strategic shortcut from Norfolk Va to Richmond Va in a way that would flank the enemy if need be.

I responded "glad they're on our side". I had wondered why the highway department was in such a hurry to rebuild that little bridge after tropical storm Gaston had caused the river under it to scour away critical soils that suppprted it. It was normally a 90 day project but it was done in 30, including Christmas and New Years day.