Concrete colors and styles over time

[JHZR2]

I live in an old town with old houses. I grew up in an old town with old houses (and slate curbs and sidewalks). One thing I've consistently noticed is that the older concrete curbs/sidewalks/driveways just look "nicer" to me.

Surely a lot of this is personal aesthetics, but I can't stand this stark white, brushed concrete that gets laid these days. Very plain and then it gets dirty and looks like trash.

The older concrete seems to be a form of exposed aggregate concrete, often with a mix of colors of stones in it, but the cement itself (the fine materials, in case I'm using the wrong terms) always seems darker. Even on stuff without the exposed aggregate, it's darker and nicer looking.

I'd suspect that some of it is the fact that it gets dirty and stained, and some of it is that limestone darkens with age. But here's the thing, sidewalks that are now ageing to the point of being 15-20 years old, which I see and know the history, still have not achieved the same type hue (darker, dirtier, yes, not the same color).

It is my impression that concrete can be ordered in colors,many that the exposed aggregate type is a different order than plain smooth concrete. So how much of the difference is styles of the ages? Was it commonplace/standard to make pigmented concrete back in the day which is not the case now? Was it common/standard to have smooth and round aggregate in the concrete then which is not common now?

Just curious. I'm just not a fan of this whitefish concrete we see these days...

 

[eljefino]

I just overheard an interesting anecdote... the Stanley brothers, of Stanley Steam engine fame, came up with a concrete recipe that included (salty) ocean beach sand and a "secret ingredient". I've been on 100-year old sidewalks made from this technology and they are a darker color, with bigger rocks in the mix (not sifted like today).

The secret ingredient? Asbestos. This concrete has periwinkle shells in it if you look halfway close.

Could asbestos perhaps have been your secret ingredient as well? They do put fiberglas in modern mixes, FWIW.

 

[Mystic]

The Romans had some concrete that would harden underwater. I think they used volcanic material but I don't know the ingredients.

I looked it up online. Here is one article on it:

http://www.brighthubengineering.com/concrete-technology/78929-roman-concrete-technology/

 

[bbhero]

In almost all of the high end neighborhoods around me they use the small aggerate mixed in the concrete. It's in all of the driveways and sidewalks. It is also a fair amount more expensive than the white concrete.
I agree with you 100%. The best looking concrete is the one with the small rounded aggerate mixed in it. Matter of fact my step father and moms whole driveway is made up of it. And it really looks very nice indeed.

 

[Milkman]

I have been driving a concrete mixer and doing QA/QC work on concrete for about 7 years now. The "white" concrete you see now is a result of the way cement is made now and to a lesser extent the fly ash that is added to most mixes. Around here, blast furnace slag used to be added to the mix. That resulted in the residual iron in the slag "rusting" and turning the concrete a slightly brown color.

 

[Shannow]

Originally Posted By: Mystic
The Romans had some concrete that would harden underwater. I think they used volcanic material but I don't know the ingredients.

I looked it up online. Here is one article on it:

http://www.brighthubengineering.com/concrete-technology/78929-roman-concrete-technology/


Ahhh, one of my favourite diversions from mechanical engineering is ancient concrete.

The Romans used volcanic ash, which was called pozzolana, and subsequent materials are graded by their "pozzolanic" properties. Due to it's nature, it has alumina and silica in it, and some of that silica is amorphous (glassy).

When mixed with calcium hydroxide (hydrated lime), a reaction takes place, and it forms a very strong matrix, and will chemically bond to the aggregate, whereas regular Portland Cement will form a matrix around the aggregate, but not incorporate it.

The Roman Concrete has stood 2,000 years, and our modern version, the current version will be lucky to stand for 2 centuries...it's a different chemical process.

There's strong evidence that the Egyptians (actually, rumour has it the phoenecians) understood the process, and used it partially for the pyramids (Google professor Davidovits). They used Natron, which was high in Sodium Carbonate, which mixed with burned lime make a caustic calcium rich constituent.

Modern equivalents to the roman concrete use power station fly ash (thus my hobby)...some of the "geopolymers" produced from power station fly ash can exceed 100MPa (concrete is like 35).

I've done simulated roman concrete with 4:1 flyash to hydrated lime, it's light and pucks made from it do well in the weather.

My favourite more advanced version involves flyash, then wetting it with a soluble silicate (I harvest that from head gasket sealer), until it forms a plasticene paste, then add caustic soda (lye), which heats, dissolves the silicas, and then polymerises, to form a light, durable structure.

If you pick the right ingredients, you can make some pretty stuff.

As the JHZR2's observation, there is a massive massive difference between modern and old concrete.

In the "old days" Portland Cement was formed, and milled quite coarsely. The standard for concrete is the "28 day strength", and that's what it tested to.

Old concrete had large quantities of large particles, and it's strength/age curve went on nearly forever...a crack would, and could self heal as moisture and air got in.

Modern concrete is super finely milled, and requires minimal amounts to achieve it's 28 day strength...then that's it...it's got no alkalinity reserve, it's got no self healing, and it starts carbonating...like I said, it will not last 200 years.

Old concrete can be beautiful...

Here's my back stairs, where you can see the inclusions of blast furnace slag

Here's some houses in the district that are made from lime/ash

 

[Silk]

My grandfather walked across the road and used sand from the beach - all his concrete had shells in it. Obviously a common thing to do as I've seen shelly concrete elsewhere...and probably in other parts of the world too.

 

[Pop_Rivit]

It just makes sense that concrete color and finish varies from age and regional materials. Personally I don't care for any exposed concrete, the older stuff appears dated and has an inner city look to it; the newer stuff is reminiscent of the soulless suburbia look.

 

[JHZR2]

Originally Posted By: Pop_Rivit
It just makes sense that concrete color and finish varies from age and regional materials. Personally I don't care for any exposed concrete, the older stuff appears dated and has an inner city look to it; the newer stuff is reminiscent of the soulless suburbia look.




No kidding it makes sense, but it appears that your grumpiness trumps any insightful interaction.

Note that the question was "color and styles over time". Things like iron furnaces (we make much less here than years ago, Id guess) and their influence in the mixes is reasonable.... But I asked about styles and how style has changed over time (which would influence dopants). Industrial processes may also play in to it.

How a braggart who built a large home on virtually worthless land has any useful basis in what determines an inner city look or what dictates suburbia or anything else is beyond me. And by the way, your 20 year old house is now dated too...

And plenty of people who build and own far higher end homes then yours will ever be, beg to differ. Nothing like dirt or gravel to imply that you're house rich, dirt poor and couldn't finish your hardscaping. And heaven forbid if you have asphalt. Yuck.



So, others who care to shed useful information are welcome.

 

[JHZR2]

Originally Posted By: bbhero
In almost all of the high end neighborhoods around me they use the small aggerate mixed in the concrete. It's in all of the driveways and sidewalks. It is also a fair amount more expensive than the white concrete.
I agree with you 100%. The best looking concrete is the one with the small rounded aggerate mixed in it. Matter of fact my step father and moms whole driveway is made up of it. And it really looks very nice indeed.


Agreed. Exposed aggregate + paver/bricks is typically done on high end homes. But back in the day, it seems to me that exposed aggregate was the standard process for finishing. Its on every one around here, and were not a multi-million dollar neighborhood... Thus my curiosity.

 

[tom slick]

I notice the concrete contractor's name stamped in old work but not in newer work.
I've done some exposed aggregate work. It requires a different sand and aggregate mix than regular concrete.

Also keep in mind that concrete is made of regional materials so the old concrete materials may have come from a different quarry than the newer work and may have weathered differently.

 

[hattaresguy]

Typically if your willing to pay you can order whatever you want. Very few people are willing to pay for anything beyond the 4k psi 1/2in aggregate mix that makes up most sidewalks and aprons.

You can get black aggregate mixed in if you want, or different color dyes.

But the cost is high, your going to start getting to the $200 a yard range really fast.

Which is why I just use pavers.

Belgian block is the best apron if your looking to spend money.


Tastes change, back in the day clover was considered part of a normal lawn, these days its a weed. Concrete poured 100 years ago was typically made from local materials and was of varying quality. Hence why you see shells in concrete poured next to the beach!

 

[eljefino]

Originally Posted By: JHZR2

Note that the question was "color and styles over time". Things like iron furnaces (we make much less here than years ago, Id guess) and their influence in the mixes is reasonable.... But I asked about styles and how style has changed over time (which would influence dopants). Industrial processes may also play in to it.


Yup, my grandpa worked in the Youngstown OH area in the 1930's for an operation called "Standard Slag"; the steel process at the time was (apparently) inefficient and produced copious amounts of slag which was integrated as (useful?) filler into concrete.

After WWII they were better at making steel, less waste, so they had to mine more aggregate. But they still called themselves a slag company.

 

[sleddriver]

As one with a keen eye for detail, I've noticed various shades and weathering of building materials, including concrete.

The major river dams built here during the late 30's/early 40's are interesting to look at up close, especially when one considers the age, the time and their construction. One archy friend said that concrete is still curing!

Another of similar interest, but even older is the concrete poured to raise the island of Galveston after the big hurricane around 1900 completely flooded it. The "concrete-walk" and apron have sure seen a lot of history & weather since then. The jeties extending into the gulf, are formed from huge granite blocks...and very slippery in places, to walk on.

Re: Mystics comment...concrete will cure underwater. It's an exothermic process. Here freshly poured foundations should be sprinkled and covered due to the blazing heat. Many aren't though.

 

[MNgopher]

Concrete color is a function of a lot of things. While the general ingredients in redi-mix haven't changed that much, there are differences from older concrete. Sources of portland cement change over time, as do the sources of sand and aggregate. The portland cement ratio itself may be different through the use of fly ash (currently the most common pozzolanic material these days - a significant by product of the increased focus on air emissions at coal fired power plants). We've also changed the mix a bit with various additives to accomplish various goals.

The biggest thing these days is people actually like the whiter color. You may not, but a lot of other people do and expect it. In significant time, they will darken, but that takes a long time.