crack movement gauges anyone know about them

huangyhg

crack movement gauges anyone know about them?
does anyone know where i can get some plastis gauges that are glue to a concrete wall over an existing crack in order to detect future movement. i know i've seen them beofre, but google is letting me down on this one.
check out our whitepaper library.
avongard crack monitor is the one i am familiar with.
thanks a million jike..just what i was looking for!
re  
i often install concrete nails (drill 1/8" dia holes and install as two hardened steel pins and then use a dial gauge vernier caliper to measure.  this works quite well.
dik
thanks for your input...i will have my client order the avonguard gauges...i think we can also measure lateral movement using feeler gauges between the two sides...thanks again for your responses...
daveh6729....i have used the avongard monitors and the method dik described.  the old soiltest company used to sell a kit that was a fancy way of doing what dik described, but two hardened pins shot, hammered, or drilled into the concrete will work just fine.
one caution on any of these methods...try to normalize your readings by taking them at about the same time and temperature (if possible).
in the past i have used demec pips and vernier calipers.  you fix three or four pips around your crack and just measure between them with the calipers.  dead easy.
and install th'e pins 'square' to the wall... on the concrete nails i use, there's a little bright coloured rubber bushing for centering in the gun.  i press this against the concrete substrate so that it's less likely that you're measuring from different locations on the pin.  measurements are taken ea day, then ea week then ea month for six months and then bi-annually depending on the movement observed.  by using a vernier caliper, it is possible to locate the pins abour 4" apart and not as likely to be affected or affect the edge of the crack.  if the movement exceeds the 6" capacity of the caliper, then you likely have a problem <g>.
dik
i've used a whitmore strain gauge in the past.  seemed to work well.
good stuff here.  never thought about using the pins or nails.  thanks.