Hammer sounding or sounding hammer

[JoeBaseplate]

I am going to be on site with some other folks next week to take a look at some concrete cracking. I am curious about hammer sounding, I have never done it. From what I have read a common hammer can be used to strike concrete and the sound generated is indicative of concrete quality. For those who have experience doing this, is the hammer a special type of any common hammer will do? Also, how hard are you supposed to hit the hammer?

I won't be doing the hammer sounding but I want to know at least the basics of it.

 

[msquared48]

Use it all the time to tell whether or not a CMU cell is grouted. Just a normal framing hammer works well for me.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[BAretired]

I don't think the hammer test will convince the unbelievers, but I suppose good quality concrete has a ring to it which could be discerned by the human ear. However, it is not clear how the ring could be quantified in any meaningful way.

BA

 

[msquared48]

I have never used the method to field test the integrity of concrete, and doubt that I ever will.

As for striking the CMU with the hammer, we "first do ho harm" to either the CMU or the framing hammer. Those things are expensive!

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Ron]

Hammer sounding is primarily done to check for voids, as Mike indicated. Yes, "sound" concrete has a certain "ring" to it, but as BAretired noted, that is not quantifiable and is very subjective.

Cracks in concrete often have little or nothing to do with the integrity of the concrete. In fact, higher strength concrete will often have more significant cracks because most cracks are caused by shrinkage, particularly with slabs on grade.

You can check for voids under the slab using a wooden dowel, end down, dropped straight through your hand and caught on the rebound. You will only need to drop the dowel 6 to 8 inches. When you have voids in or under the slab, you will typically hear a dull thud rather than a resounding "ring". The dowel I use for this is about 1" in diameter and 5 feet long. Sound on both sides of cracks and joints to check for curling.

 

[Zambo]

Hammer sounding doesn't seem like the first and most important form of testing.

1. are the cracks in concrete walls? Is there any particular pattern to the cracking?

2. are the cracks on floor slabs?

 

[SkiisAndBikes]

I have done a fair amount of sounding surveys, either with a hammer or for larger horizontal areas via dragging a chain. I often will use just a regular hammer, although there are guidelines out there somewhere that standardizes the equipment.

I use hammer tapping to detect delaminations in reinforced concrete slabs/beams/walls/columns. The delams are primarily due to corrosion of the reinforcement and can result in cracks showing on the surface. The hollow sound you get when hammer tapping delaminated concrete is very very different from that of solid concrete. You don't have to hit very hard. If the concrete is cracked due to reasons other than delaminations, the hammer tapping will likely not provide any useful information.

 

[a2mfk]

I think its a decent, quick, albeit rough method to find "areas of interest" where you may need to do additional testing. Like others, I have only used it to locate grouted cells and detect voids under SOG. But I did some research online a while back and there are some pretty sophisticated equipment versions of this test out there that companies use, but more for large sections of pavement and warehouse slabs..

Like the others want to know- what is the structure?

 

[ToadJones]

with regard to hammering on CMU's. I'd do so VERY gently. I have pounded perfectly round holes in hollow CMU's many times for running conduit. It takes very little effort.

 

[bylar]

I don't think he is talking about a carpenters hammer. As I recall many years ago the concrete company had such an instrument and it doesn't rely on sound but rebound and is guaged. It was used to find an area of a slab that had concrete with nsufficient cement. The cement hopper had hung up.

 

[SkiisAndBikes]

Perhaps would they be looking at a Schmidt Hammer test? Used (sometimes) to test the relative strength of concrete insitu.

 

[SLTA]

Anybody want to see my thesis on delaminations in concrete and a comparison of impact echo equipment vs a sounding hammer to locate said delaminations? All 200-odd pages of it?

A regular hammer works just fine. Chains dragged or flipped work well, too, as does a golf ball bounce. Well, these work great for finding large-ish areas of delaminations, not so great for small areas or cracks. No need to hit hard - you just listen for a difference in sound.

What exactly are you going to be doing? Type of material? Structure use/age/location? Wall or slab?

 

[nuche1973]

I use the steel toe in my shoes. It works great and I don't have to worry about losing the hammer or draging a steel chain. Just walk around the site and toe kick the slab. I've also seen guys use the swiss hammer (Schmidt hammer) on the slab.

There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.