Can anyone educate me about cement?

[Wrecked944]

Does anyone know what the differences are between various cement products? I understand, for instance, that a fair number of home builders are making kitchen countertops out of cement these days. I also understand that there is a product available to side one's house made from cement. I always assumed cement was cement. But clearly I am wrong. So, for instance, if I were going to replace my kitchen counter with cement, could I do it myself and what type of cement product would be hard enough to withstand rough use? Is there stuff you can beat on with a hammer that won't chip or dent? Can you make a work bench top out of cement?

[M.D. Holloway]

Here are some good sites - you are better of looking into concrete than cement. Cement is something that holds concrete together.

http://www.concrete.com/index.htm

http://www.aci-int.org/general/home.asp

http://www.concretenetwork.com/

http://www.worldofconcrete.com/

I went to the World of Concrete trade show a few years ago - everything and anything you ever wanted to know.

[M.D. Holloway]

Also - they make inground pools around here from Gunite. Here is something interesting I found

Gunite
"Gunite" is a trade name for "dry gunned" concrete, invented and patented by a North Carolina man. The term "gunite" has been used so much that, to most people, it means spray applied concrete. People often talk about a gunite pool -- meaning a concrete pool where the concrete is pneumatically applied or sprayed in place using air pressure. Many of us in the concrete spraying business have started using the term "dry gun" to delineate this process.

"Dry gun" means the cement and sand are injected into an air stream conveying it to the nozzle. The nozzle operator then adds the water at the nozzle and has total control of the water-cement ratio. The delivery hose of the mix is generally quite light, as the hose is mostly filled with air containing the mix of cement and sand.

Dry gunning allows concrete to be placed drier than most "wet gunning," but that is not always a plus for dome building. Often the concrete is stacked at a very heavy thickness. This can be a disaster for an Airformed structure. Operator training is very critical and can mean the difference between success and failure of application. The danger of dry gunning the concrete on a Monolithic Dome increases as the size of the dome increases.

Shotcrete
"Wet gun" means the wet (already mixed) concrete is pumped to the nozzle. Air is added at the nozzle to carry the concrete mix to the target -- again pneumatically applied. We call the system "wet gunning." Here too operator training is important, but not quite as technical for wet gunners. Mistakes in application are usually far less critical than with dry gunning in Monolithic Dome construction. Rebound, or the waste created by sprayed concrete falling to the floor, is usually half as much for shotcrete as compared to gunite.

Equipment
Dry gun equipment is totally different from the wet gun. The air needed to transport the concrete is at least four to six times greater than that needed for the wet gun system. For wet gunning, a pea rock or grout pump is usually utilized. Monolithic has updated and improved the small peristaltic pump in an effort to provide more affordable equipment for wet gunning.

For house-size domes either system will work. But, for the novice, the wet gun is my recommendation.

The dry gun does not have the capacity for large domes -- 50 feet in diameter and bigger. Dome Technology once had a five-man crew shotcrete 238 cubic yards of concrete in one day! They can routinely apply 100 plus cubic yards. This is well beyond the capacity of a dry gun system.

[trekkor]

Pretty interesting, thanks.

KT

[M.D. Holloway]

I remember when I was 4 we moved into a 120 year old Victorian Farm house in Connecticut. My Folks spent about 25 years re-doing the inside and most all of the outside to period luster.

One of the first projects I watched (and helped) my Dad do was to mix some concrete for a back porch. He had found boxes and boxes of large blue Mason jars. He had me dump them into a small ashcan and pulverize them with a baseball bat - like I was churning butter! He used the glass fines as aggregate in the concrete. It gave it a great blue sparkling luster! He said it would give it durablitly.

My Mom came out and nearly had a fit stating that those jars (back 39 years ago) were worth some good cash. I must have smashed around 4 doz!

the Folks sold it 15 years ago. I visted that house a few years ago and that back porch looks just as good as the day we made it!

[trekkor]

Did you take any pictures of that?
Sounds pretty good.


KT

[M.D. Holloway]

I wish I did - they took plenty when they had it on the market but it was over the insides and a few of the outside.

[snowman]

I own a house, built in 1901. The basement is poured concrete. The walls, 24" to 30" thick!!!, the floor is about 15"thick. This concrete is as good as the day it was poured, no flaking, or anything, just rock solid. We had a flood in 72. They had to drill 2 holes thru the wall for gas and water. It took them almost 2 weeks to bore a 2" dia hole thru this wall!!! They used rail road tracks for reinforcing in the porch and walls. They used steel I beams for a frame.

The guy that built the house was a bridge builder, so it seems to make sense, a little, anyway.

Anyone know when the earliest poured concrete was used in homes???

[M.D. Holloway]

The foundation in the house I grew up in was huge blocks of granite. The house was built in 1860. Not sure it they did that because granite was convenient or because concrete was not.

[red-beard]

Originally posted by snowman
Anyone know when the earliest poured concrete was used in homes???

Late 1800's. The first concrete houses were designed and built by Edison. It was his idea for cheap affordabe housing for the masses. Even the cabinets were poured concrete.

Concrete was pretty rare as a building material until the turn of the last century. Edison had the first reinforced concrete buildings made in Schenectady, NY. At least 2 of them are still in use today. The thrid one was knocked down 10 years ago, over an entire summer. The design was "overbuilt" by using 100 as the safety factor.

The only problem we had while we occupied Building 40, was that the concrete was beginning to break off and rain down on our false ceiling. Occasionally, the piece would be big enough to crash through the false ceiling...

[Porsche-O-Phile]

Thank you. It irritates the hell out of me when people use the words "concrete" and "cement" interchangeably. They're not the same thing. Cement (as Lube correctly pointed out) is a constituent ingredient of concrete and is not nearly as strong on its own as a fully-developed concrete matrix including coarse and fine aggregates and possibly one or more admixtures.

It is possible to do some pretty amazing stuff with concrete - there are compressive strengths over 20,000 psi being attained with certain admixtures (notably fly ash), there are lightweight concretes that can span much further than previously possible, etc. It's a pretty good material overall although one does have to consider whether it's appropriate for the given use/application they're considering or not. Its R value is extremely low, it is extremely weak in tension (necessitating the need for steel reinforcing, and steel is $$$ right now), it has a somewhat-high up-front cost of installation (you essentially end up building two structures, one out of wood, one out of concrete and then tearing the wood one down), etc.

If you want an absolutely indestructable countertop I'd say it IS possible to do with concrete, but there are other things that can be made similarly strong. Certain plastics now are amazingly tough/durable. I suppose you could also go with plate steel. . . Might be an interesting little design project. Also consider that the heavier the countertop, the beefier (and more expensive) the support structure required.

[RickM]

Here's some pretty good DIY articles on making concete countertops.... http://www.naturalhandyman.com/iip/author/dcn/conccounter-a.shtm

These have been on the Net for quite sometime.

[vash]

it is all about the aggregate. for a countertop, i would assume you dont want 1.5" large aggregrate. i think they look damn slick, and would love to got that route partially. you thinking about the regular grey color? or adding a color admixture?

[Porsche-O-Phile]

Originally posted by vash
it is all about the aggregate. for a countertop, i would assume you dont want 1.5" large aggregrate. i think they look damn slick, and would love to got that route partially. you thinking about the regular grey color? or adding a color admixture?

You know - a conventional concrete pour cut & polished to show the cross-section of aggregate stones and such might make a pretty darned cool looking countertop. Almost the same thing as a polished granite countertop, only with concrete. I haven't seen this done though. It'd be pretty innovative.

[vash]

that would make a cheap countertop expensive again. i have seen it done. they form it up, and pour it, polish it. looks slick and you can get really great shapes. this guy did a kidney shaped island. no way you get that with granite.

when i do my countertops eventually, i want to find a salvaged highschool chemistry class countertop and use that for an island and do the rest in soapstone. i would leave all the "chache love love jenny" graffiti and everything.

[M.D. Holloway]

Here is a great paper on repairing and maintaining concrete. it is an
Introduction to Repair and Maintenance of Concrete Floors Sponsored by: Structural Preservation Systems Inc.
Length: 20 pages
Content Type: White Paper
As the concrete infrastructure in industrial plants and warehouses continue to age, there is an increasing need for sound, proven condition evaluations and repair strategies for reinforced concrete structures. After years of service and exposure to severe environments, the aging industrial infrastructure that store, manufacture, process, treat and dispose of products are in need of substantial repair, restoration and strengthening.

Here is the link, you just have to give some info to download it - it is safe. It comes from Plant Services - I write for them from time to time: http://pls-media.com/lrd3_AAR1tAAACO4B

(hope you can open it up...)

[Wrecked944]

Just for the record: You guys are beyond amazing. I knew I could ask any question - no matter how obscure - and get expert answers. Thanks!

[M.D. Holloway]

Originally posted by vash
... i want to find a salvaged highschool chemistry class countertop and use that for an island and do the rest in soapstone. i would leave all the "chache love love jenny" graffiti and everything.

tell me about it, I want to get my hands on a chem labs benchtop and fume hood, get some glassware, water, N2 and vacuum hook up and start some chem work in my garage. I have about 300 ideas that I would love to explore. The neighbors might think I would be cook'n meth though...

[vash]

na, the truly gifted meth producers do their best work cooking in the toilet the tank is the "workbench" to store the mise en place.

[charleskieffner]

concrete will and this is scientifically proven, do the following:

1)get hard
2) it will leak
3) it will crack
4) it will not burn
5)and concrete should never be mixed with ocean sand and ocean water. why? just ask the u.s. army corp of engineers and the pier they built in the 1900's off lahaina harbor,maui,hawaii! (clue........its underwater now!)