HWg-CS54: Monitoring of concrete hardening (temperature, humidity)

Technical description

• HWg-Ares 12 is a GSM temperature/humidity sensor with data logging.
• External outdoor temperature/humidity sensor measures temperature from –50˚C to +125˚C (–58˚F to 257˚F) and humidity from 0 to 100% RH.
• Up to 3 temperature/humidity probes can be connected to HWg-Ares 12 (if more probes are needed, HWg-Ares 14 supports up to 14 probes).
• The Ares unit is configured over USB using a common Windows notebook.
• The Ares unit can be configured remotely over GPRS using the SensDesk portal.
• When the configured temperature/humidity thresholds are exceeded, Ares sends a text message alert to configured mobile numbers. In this case, the alert means that the concrete humidity is OK and the construction can continue.
• HWg-Ares communicates over GPRS, a SIM card from a mobile service provider is needed. When text messaging is not sufficient, a data plan is needed. A M2M data plan is enough, Ares only transfers small volumes of data.
• HWg-Ares can also e-mail its temperature and humidity logs as CSV attachments. Using the HWg-PDMS application, data can be plotted in a chart or exported to MS Excel.

Why monitor concrete hardening remotely

Since the concrete drying process is very slow, you don't have to go to the location every time you want to check the humidity on the concrete floor. Concrete is very fragile material for cracking if it is overheated.  Before the concrete is dry enough to be watersealed, tiled or carpeted again, it takes weeks or months to dry. With a remote sensor you don't have to go to the location every time to check if it is dry enough. Remote monitoring over GSM saves a lot of time and work.

Testing the sensor by Lasse Laaksonen from Finland

To measure the moisture of a concrete with the official Finnish building instructions, you have to drill min. of 10mm diameter and min 60 mm deep drillhole in to the concrete. Then you have to vacuum it clean, seal it and let it stabilise for 72 hours. After that you have to put the sensor in the drillhole, seal it again, and wait for the sensor to stabillise from 15min to few hours depending on the sensor model. With this method, it is possible to get accurate RH of the concrete.
I 've been testing the sensor on 2 week old concrete, for 5 days with humidity of 98-99% Rh. I had to drill a 16mm hole to fit the 15mm diameter of HTemp Outdoor-sensor into the hole. After that I vacuumed the hole, and put the sensor in it, and sealed it. After 24 hours stabilising in the drillhole, the measured value ended changing, so I knew it was stabilised and the measured values were correct. This also made the process a lot faster because instead of 72 hours, I got the same readings already after only 24 hours.
I got the periodical report every 12 hours to my email (or as often I want ). If I wanted to check the humidity in realtime, I just sent a "Status" SMS to Ares 12, and immediately got the answer to my mobile phone. After 5 days, I took the sensor out of the concrete, let it stabilise to the room humidity and temperature in appr. 15 minutes time and showed exactly the same figures as the Gann RH-T 37 EL and Trotec TS 240 SDI moisture/temp. sensors we also use. Testing was done indoor @ 22C temperature and 55%RH.
Preparing the Ares 12 and sensor
Since I'm not a computer wizard, and the instructions were in English, it took me approximately 2 hours to create email accounts and configure the Ares to work with my phone and email accounts. This was the thing I was a bit afraid of, but everything worked as the instructions said. And of course I need a GPRS/GSM SIM card ( I use Sonera network SIM ) to function with the Ares. After I did all this, I just started measuring.

Temperature and humidity charts

• HWg-Ares periodically sends data over GPRS as e-mail attachments to a specified e-mail address.
• The HWg-PDMS software on a PC downloads the e-mails from the configured account.
• Graphs can be viewed directly in HWg-PDMS.
• Measurements can be exported using the XML interface.
• Measurements can be imported to MS Excel for further processing.