Concrete Density.

Does anyone know of a simple way of finding concrete density. I'm searching for a void beneeth a large concrete slab.

Nasa:
Does anyone know of a simple way of finding concrete density. I'm searching for a void beneeth a large concrete slab.

Sounds like you need a ground radar survey.

Sonar might also work. Or use seismography, like they do with oil fields. Hook some microphones to a multi-track recorder and whack that slab with a hammer. :slight_smile:

Nasa:
Does anyone know of a simple way of finding concrete density. I'm searching for a void beneeth a large concrete slab.

Sure! When all is quiet around the slab, hammer it with a steel rod and listen for the difference in sound. Supported concrete will "thud" and concrete without support will "ring". Concrete is flexible. It will move when hit. Not much, but you can tell the difference.

Paul

johnwasser:
Hook some microphones to a multi-track recorder and whack that slab with a hammer. :slight_smile:

Stick of dynamite would be much more fun . :slight_smile: :slight_smile: :slight_smile:

Looking for Jimmy Hoffa?

Not sure what you mean by "finding" the density. FWIW, structural engineers usually use a density of 145 or 150 pounds per cubic foot for "normal" weight concrete when calculating the weight of concrete components of buildings and other structures.

If you are looking for a void is it in the concrete or underneath the slab.

If the former measuring the thickness will work.

If the latter both impact echo and ultrasound are unlikely to work.

The reflection is normally from the concrete boundary layer.

EDIT

If no one comes along i suggest you contact an NDT specialist company for advice.
There may be more modern techniques i am unaware of.

Ground radar was not available in my day and may be up to the job.
Either way its unlikely to have a diy solution, the equipment is expensive.

We used to regularly drill holes for problems like this.

Another method involves using a mole under the concrete slab and inserting a radionucleide up the pipe.

Nasa:
Does anyone know of a simple way of finding concrete density. I'm searching for a void beneeth a large concrete slab.

IS this domestic ??

Are you by any chance looking for a radon sump ?
There is another way of finding them.

About 30 years ago, while building a large metal home on a hill overlooking a major tributary we discovered a shaft barely large enough for a man. The shaft was cut square and the walls were lined with rough wooden timbers. At the time, the owner was in a hurry so the hole was covered over and a slab was poured over the opening.

The owner is now deceased and a fire that ravaged our countryside destroyed the home.

The shaft was not marked nor open when it was first discovered from excavating for the foundation of the home that required an earth berm on one side. I recall a gray clay used to seal the timbers in an otherwise sandrock formation. It is possible that the shaft might be a water well but I know that it is more than 100 years old as my family moved there just over a hundred years ago and they had no knowledge of this.

The location is about 52 miles from where the Spanish were defeated by about 6000 native American Indians in 1759.

Spanish were defeated by about 6000 native American Indians in 1759

i.e. 52 miles from Spanish Fort, Texas?

Yes. This overlooks the West fork of the Trinity river.

Nasa:
Yes. This overlooks the West fork of the Trinity river.

Now, please don't anyone laugh. This is not Arduino related in any way, but a possible way for the OP to discover a water well.

Have you requested the help of a "witcher"? I don't know how or why they work, but have personally experienced finding a siphon water pipe on top of a hill between a house and and the spring supplying the water.

Paul

In the Uk they are called dowsers (not dossers.)

Years of experience and training , only tools needed are a pair of knitting needles , or a bent coat hanger if you are poor.

Of course it may not be a well.

Could be buried treasure given the location.

Start a rumor and get it dug up for free . :slight_smile:

Dowsing is a pseudo-science that has not shown evidence of being more effective than chance in controlled studies.

http://skepdic.com/dowsing.html

"the sad fact is that dowsers are no better at finding water than anyone else. Drill a well almost anywhere in an area where water is geologically possible, and you will find it."

Dowsing is a pseudo-science

+1
Consult a dowser if you also believe that the motion of the distant planets controls your love life.

jremington:
+1
Consult a dowser if you also believe that the motion of the distant planets controls your love life.

Well them distant planets dont seem to be moving much.

I have had very good luck in locating active buried water and power using brass rods with sweaty palms. They align themselves with the spontaneous potential. As far as witching for water it might be possible.

Many years ago there was a development of a sensor that could be flown over an area and could detect hydrocarbon deposits. Hydrocarbons are an excellent insulator. The guy had great success unfortunately his designs died with him.

Spontaneous potential was first used with electronics by the Schlumberger brothers in the earliest well logging. As different formations had different static charges this was used to find the oil deposits apart from water deposits. They didn't have insulated cable to lower into the well so that used friction tape, a cloth tape saturated with a rubbery substance or maybe more like pitch, wrapped around the wire cable as they lowered it into the well. They used a galvanometer to see the results.

I know close proximity of this shaft I want to locate. Most likely we will use a large piece of wood to thump the slab and listen for the difference.

Due to the age, small size and the amount of work, the distance to where wood for the timbers had to travel that were used in making of the shaft, I think it might have been of great importance.

The first thing is to clear the rubble from the destroyed home so work can begin.