(10-01-2008, 03:39 PM)rthompson Wrote:(09-30-2008, 08:01 AM)Chris Reynold Wrote: I drilled several test holes, inserted sleeves and returned to the first test hole about 15-20 minutes later. Inserted a RapidRH reader in the first test hole and got a temp. of 85 and a RH of 75. The other test holes were in this same general range. Later in the day I took readings and the temp was down around 70 and the RH was up around 80. Can anyone help me understand what is going on?
Friction, when you drill a hole in concrete the speed of the drill creates enough friction to dry and heat the immediate area in the hole. That is why the relative humidity was down and the temperature up. This is why the immediate readings are not as accurate as those after an acclimation time.
I was just in a meeting where Howard Kanare, Sr. Vice Principal Scientist with CTL Group, was speaking. The question in regards to temperature and RH were brought up. Howard’s response to this was that in the many tests performed by his lab, they have concluded, by using a temperature gauge to measure the temperature of the concrete, that the heat from the drill very quickly dissipates. He concludes that the concrete is a very good heat sink.
In addition, one of their processes has been to take the sensors (aka: sleeves, barrels) out of the packaging, lay them on the concrete while they are drilling their holes and prepping them for the sensors. This gives the sensors time to acclimate to the environment of the concrete, rather than the temp of the trunk of the car or other environment from which the sensors have been brought from.
Our data here at Wagner shows that our Rapid RH meters read approximately 3% of the final reading within 20 minutes of inserting the sensors. However, you will always want to follow what ASTM F2170-02 specifics for your final report.