Vagueness and the Aftermath - A sporadic diary

[outragous76]

oh no! you did that on purpose just to make me post in your diary again didnt you!

arg - it could lead to an exceedingly long post - you really wanna know?

Its not strictly frost action as it doesnt affect concrete on its own...............

lemme know if you really wanna know and ill tend to it later - ill try and find some C&P to simplify

[RED-DOG]

Hydraulics

It fascinates me to think about airport vehicles. Trucks, vans, 4WD's, coaches etc.  spending their entire working lives driving around the same few hundred yards of tarmac.

My works van Renault Kangoo has 29k on the clock 10 years old,never been of the airport(not taxed).Speed limit 20mph on side roads 5 mph on the ramp,rarely driven more than a few hundred yards at a time,completely shagged tbf.Miss my Bedford Rascal RIP.

Stop-start work is the worst thing for road vehicles. Everything gets loads of use, brakes, clutch, gears, doors, seats, etc, and the engine never really gets up to it's optimum operating temperature.

Also, when you start an engine, it tales a second or two for the oil to get around the main bearings. That means it's running dry a lot of the time.

Give me a 100,000 motorway miles motor instead of a 40,000 stop-starter every time.

[RED-DOG]

oh no! you did that on purpose just to make me post in your diary again didnt you!

arg - it could lead to an exceedingly long post - you really wanna know?

Its not strictly frost action as it doesnt affect concrete on its own...............

lemme know if you really wanna know and ill tend to it later - ill try and find some C&P to simplify

I really wanna know. I'm interested. Why do you think I photographed it in the first place?

[outragous76]

oh no! you did that on purpose just to make me post in your diary again didnt you!

arg - it could lead to an exceedingly long post - you really wanna know?

Its not strictly frost action as it doesnt affect concrete on its own...............

lemme know if you really wanna know and ill tend to it later - ill try and find some C&P to simplify

I really wanna know. I'm interested. Why do you think I photographed it in the first place?

ok i will post lkater

concrete defects used to be a speciality of mine!

[RED-DOG]

Found reeeeeally nummy buttermilk biscuits recipe today!  They're the proper 'dip in yer gravy' type too.  Saved the link, so give a shout if ya ever get baking brave.  GG diet.

Er, I don't know if you've noticed Dawn, but we're a civilised race, us Brits.

I've had this conversation before, in a restaurant, in the States. Civilised people dip their biscuits in tea, and gravy is brown and meaty, not pale and custardy.

[RED-DOG]

oh no! you did that on purpose just to make me post in your diary again didnt you!

arg - it could lead to an exceedingly long post - you really wanna know?

Its not strictly frost action as it doesnt affect concrete on its own...............

lemme know if you really wanna know and ill tend to it later - ill try and find some C&P to simplify

I really wanna know. I'm interested. Why do you think I photographed it in the first place?

ok i will post lkater

concrete defects used to be a speciality of mine!

Sorry Guy, I tried to think of a snappy comeback but you've floored me.

[RED-DOG]

oh no! you did that on purpose just to make me post in your diary again didnt you!

arg - it could lead to an exceedingly long post - you really wanna know?

Its not strictly frost action as it doesnt affect concrete on its own...............

lemme know if you really wanna know and ill tend to it later - ill try and find some C&P to simplify

I really wanna know. I'm interested. Why do you think I photographed it in the first place?

ok i will post lkater

concrete defects used to be a speciality of mine!

I can tell by the shape of your forehead.

(Better late than never?)

[nirvana]

I love this stuff

Used to put this in all the brochures for our conferences back in the day. Marv quote

[tikay]

Hydraulics

It fascinates me to think about airport vehicles. Trucks, vans, 4WD's, coaches etc.  spending their entire working lives driving around the same few hundred yards of tarmac.

Please! Concrete, in the main.

That reminds me, I saw this damage on a railway bridge the other day. It wasn't in place where something passing underneath so I concluded it mist be either vibration or frost damage.

I'm going for frost.

Click to see full-size image.

OK. As you were.....

It's not "damage" as such, Tom, it's the simple consequence of steel reinforcement rusting, & "frost" is, sort of, only a small part of the answer. Concrete has great compressive strength, but no tensile strength, so in loadbearing structures (bridges, for example) has to be reinforced, with, in essence, a lattice of steel reinforcement. (Used to be BS 4483, no idea of the modern equivelant).

Once water is able to reach the steel reinforcement inside the concrete, it starts to oxidise, or rust, & when it does so, it expands, & the expansion causes the concrete to "pop". Once the process begins, more & more steel gets exposed, rusts even more, & so on, & it is irrepairable really.

When the concrete is cast, some sepearation between the steel & the concrete surface is needed to prevent this, that's called "cover", & cover would normally be something like 25mm, or in a quality structure, or something like a bridge, as much as 40mm or even 50mm. To achieve this "cover", concrete "spacer blocks" are used, there are tied to the steel & sit hard against the shutter, thus ensuring adequate cover.

When the RE checks the steel reinforcement before the concrete is poured, this is the main thing he looks to check, as lack of cover is fatal to reinforced concrete in temperate climates.

Unfortunately, back in the boom days of the 60's & 70's, poor quality workmanship & shoddy standards meant many of our bridges & flyovers were not constructed with adequate cover, & as a consequence, are now "popping" something shocking. If you drive along the A4 in West London under the elvated section of the M4, you will see that every beam has "popped", & soon enough, that structure will need all the beams completely replacing, it's in a right state.

In this photo, (one of the several hundred beams that support the Elevated Section of the M4 in West London) you can actually see the steel reinforcenent "grinning" through, as it's known. Soon, all the concrete will pop, & the integrity of the structure will be seriously threatened. Every single beam on that elevated section has the same problem. The elevated section of the M6 in the Midlands (Beston Viaduct, just south of Grosvenor Walsall) has precisely the same problem.

[RED-DOG]

Hydraulics

It fascinates me to think about airport vehicles. Trucks, vans, 4WD's, coaches etc.  spending their entire working lives driving around the same few hundred yards of tarmac.

Please! Concrete, in the main.

That reminds me, I saw this damage on a railway bridge the other day. It wasn't in place where something passing underneath so I concluded it mist be either vibration or frost damage.

I'm going for frost.

Click to see full-size image.

OK. As you were.....

It's not "damage" as such, Tom, it's the simple consequence of steel reinforcement rusting, & "frost" is, sort of, part of the answer. Concrete has great compressive strength, but no tensile strength, so in loadbearing structures (bridges, for example) has to be reinforced, with, in essence, a lattice of steel reinforcement. (Used to be BS 4483, no idea of the modern equivelant).

Once water is able to reach the steel reinforcement inside the concrete, it starts to oxidise, or rust, & when it does so, it expands, & the expansion causes the concrete to "pop". Once the process begins, more & more steel gets exposed, rusts even more, & so on, & it is irrepairable really.

When the concrete is cast, some sepearation between the steel & the concrete surface is needed to prevent this, that's called "cover", & cover would normally be something like 25mm, or in a quality structure, or something like a bridge, as much as 40mm or even 50mm. To achieve this "cover", concrete "spacer blocks" are used, there are tied to the steel & sit hard against the shutter, thus ensuring adequate cover.

When the RE checks the steel reinforcement before the concrete is poured, this is the main thing he looks to check, as lack of cover is fatal to reinforced concrete in temperate climates.

Unfortunately, back in the boom days of the 60's & 70's, poor quality workmanship & shoddy standards meant many of our bridges & flyovers were not constructed with adequate cover, & as a consequence, are now "popping" something shocking. If you drive along the A4 in West London under the elvated section of the M4, you will see that every beam has "popped", & soon enough, that structure will need all the beams completely replacing, it's in a right state.

In this photo, (one of the several hundred beams that support the Elevated Section of the M4 in West London) you can actually see the steel reinforcenent "grinning" through, as it's known. Soon, all the concrete will pop, & the integrity of the structure will be seriously threatened. Every single beam on that elevated section has the same problem. The elevated section of the M6 in the Midlands (Beston Viaduct, just south of Grosvenor Walsall) has precisely the same problem.

Wow! What a stunningly comprehensive answer.

This "Cover" Is it in the form of an air space between concrete and steel then? I can't imagine how the steel reinforces the concrete if that is the case.

[RED-DOG]

"Grinning through". Perfect.

[RED-DOG]

I love this stuff

Used to put this in all the brochures for our conferences back in the day. Marv quote

I'm a sucker for em Glen.


You can't change the direction of the wind, but you can adjust your sails.

[kinboshi]

You can't change the direction of the wind, but you can adjust your sails.

...or choose a different seat that isn't as close to Mitch.

[tikay]

oh no! you did that on purpose just to make me post in your diary again didnt you!

arg - it could lead to an exceedingly long post - you really wanna know?

Its not strictly frost action as it doesnt affect concrete on its own...............

lemme know if you really wanna know and ill tend to it later - ill try and find some C&P to simplify

Whoops, it seems we have more concrete geeks on blonde than suspected, sorry if I stole your thunder.

Reinforced concrete was my trade for several decades, I actully ran several steelfixing & shuttering companies, for my sins.

Interestingly (?.....), when we did work for English heritage, or the National Trust, they insisted we used stainless steel tying wire, & even ss reinforcement, the cost of which is eye-popping. The ss tying wire was key, as the tying wire was closest to the surface, & as such, most prone to rusting, which, of course, ss does not.

The odd thing is that even with adequate "cover", the rust still easily attacks the ends of the tying wire (tying wire ties the steel lattice togeter, but crucially, ties the concrete spacer to the steel), so the key think was to always "nip" the ends of the tying wire off. Butterfly ties are best, as the ends do not protruide so much, but lack of attention to that tiny detail, & hey presto, hello rust, & once is starts, it cannot be arrested.

Regular malleable tying wire used to cost £15 for a 1cwt coil (50kgs), but stainless steel tying wire would cost £600 per cwt. Which was fine in itself, it was "in the price", but the problem was, everyone use to nick it, to "weigh it in", so it was not exactly an ideal material to use on unguarded building sites.

Jeez, I could not 'arf tell some tales about steel being "weighed in" by petty thieves, it was rife back in the day. Some sad personal tales there too, I'm afraid, "friends" who wanted to steal off me. I'm not awfuly keen on that sorta thing, biting the hand that feeds.

[RED-DOG]

Cover. The thickness of the concrete covering the steel and thereby keeping the air out?