October 8, 2020 at 10:56 pm #751948totallylostPro
Short story is i had some concrete poured for my shop floor then several months later after the building finally got built we noticed the surface was scratching very easy and several cracks. We contacted the company who poured it he came and looked and said he would get back to us. Well he wont. We planned to put in a 12000lb car hoist in and now worried maybe the hole thing is weak. So i took a chisel to it and it seemed pretty easily broke up even deeper then the surface. Being i did some concrete work at one time (i was the grunt) i don’t remember concrete breaking up so easy back in the day. So i want to get it tested for strength before risking my life under a vehicle and bendpak lifts states to get the concrete tested on there requirement page. I have asked every contractor i can find around here and no one knows. I even dug up my old boss from years ago and he didn’t know. Searched the net but only finding how its done not who to contact to get it done. Who do i contact or how can i get it done?October 9, 2020 at 6:14 am #email@example.comModeratorOwatonna, MN - Minnesota
You would need to hire a materials testing lab to sample the concrete. If you tell me where you are located I can search a name for you.
There are many tests they can do:
The easiest and least costly is a Swiss Hammer, which will give a very general idea of the hardness and compressive strength of the concrete.
They could core drill a sample from the floor and perform a compression test on it to determine a more accurate compressive strength.
The last is a spectrographic analysis, where they cut a very slim section of the concrete and analyze it. From this they can tell about anything about the mix that you want to know. The test runs a couple thousand dollars, but is the most accurate and will give the most information for you should you have to go after the contractor.
We have installed auto lifts in the past. In some cases, the location of the lift had to have the concrete removed and poured back with a thickened slab and a higher strength concrete. Should you get no satisfaction from your contractor, this may be an option to give you the safety you want.
The cracking may not be a huge issue, depending on whether there is rebar in the slab or how they cut control joints in the pour. The soft surface could mean that they added a lot of water at the jobsite increasing the water / cement ratio and therefore decreasing the compressive strength. The spectrographic analysis would be able to tell you this.
Photo’s would also be helpful.October 17, 2020 at 9:47 pm #752257totallylostPro
Thanks for your advice. I did finally find a place by searching construction material testing. Never thought of that one before. I found a place a state over from me and sent them a check yesterday. They are going to core drill the slab to be more accurate or at least that seems the most accurate. They also said like you did they can take a microscope to it and tell me more then i would know what to do with for about 2 grand. I will try to get some pics. I had made a video scrapping it up with a raser blade knife.
Far as adding water i seen the last bit of the poor and the last 2 trucks. I didn’t see them add any extra water but the guy who did the poor had claimed to much water came to the top.
After talking to another local business he said a couple of his customers talked to him about having the same issues with the same concrete guy using the same plant. what he said was they both are just pointing the finger at each other and nothing is getting fixed. I am guessing we will have to take him to court or something. The last thing i ever wanted to do. Most people around here are pretty decent folks but i had to find the 2 not so good folks.December 15, 2020 at 9:40 am #754203MiamicuseProFort Lauderdale, Florida
did the testing ever get completed and is your problem ever rectified by yourself or the contractor?January 3, 2021 at 4:35 pm #754767
make sure to ask for 3 day and 7 day and 28 day testing to ensure that the strength is coming along as design to avoid being to far into the project with bad concrete.January 5, 2021 at 12:40 pm #754854alanwattsPro
To complete a penetration resistance test, a device drives a small pin or probe into the surface of the concrete. The force used to penetrate the surface, and the depth of the hole, is correlated to the strength of the in-place concrete.July 14, 2021 at 2:34 am #759842jacksonnoah11ProMckinney, TX
Conrete testing a very tough job, but here are some improtant Methods for Testing Concrete Strength Measurement.
1. Rebound Hammer or Schmidt Hammer (ASTM C805)
2. Penetration Resistance Test (ASTM C803)
3. Ultrasonic Pulse Velocity (ASTM C597)
4. Pullout Test (ASTM C900)
5. Cast-in-place Cylinders (ASTM C873)
6. Drilled Core (ASTM C42)
7. Wireless Maturity Sensors (ASTM C1074)
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