Apparently the topic of cylinder testing gone wrong struck a chord with TCP readers, who wrote back to share stories similar to the one in last month’s blog. Following are just two humorous examples.
From a Ready-Mix Division Manager in Michigan:
We were producing concrete onsite at an oil refinery expansion project and a driver called back to the plant, saying the technician was failing multiple loads due to a high slump. Not only that, but the technician went further, stating that the slump number kept increasing after he pulled the cone off. So I went out to the jobsite and met the technician. He was a very nice and very young kid who had his ACI Level I, but had only been testing for about two weeks.
I checked a truck and then asked him to pull a sample and test it. He pulled the sample from three spots in the load, remixed the sample, wetted down his equipment before testing, and performed the slump test to perfection. He measured the slump and it passed at 7.5 inches on a 6- to 8-inch range. Then he did something that I had never seen. He told me to wait while he re-measured the slump. This time it failed, being at almost a 9-inch slump. He said, “See, I told you this mix was bad!”
I couldn’t help but smile, and asked him what he thought was wrong. He couldn’t see it! The technician had been testing his concrete on a crane mat that was 3 feet away from the outrigger on the pump truck. Every time the pump discharged and bounced due to the reach, it shook the crane mat and made the concrete settle. Thankfully we hadn’t sent any trucks away and could laugh about it afterwards.
From the President of an Ohio ready-mix producer:
One of my all-time favorites was when the driver called back to our batch plant and said they were getting bad air readings. I happened to be at that specific batch plant that day and went right out to the jobsite. The concrete tech was from an accredited test lab. I asked him to recheck the air content.
He was using a standard air meter. As he sampled and filled his meter, all appeared normal. But when he attached the top and ran his check, things didn't look so normal. The glass dome on the pressure gauge was missing, and when he released the pressure into the meter, he flicked the needle with his finger. I asked what the heck he was doing and he said, "well sometimes the needle is sticky." Mystery solved!