The TORQ-TEST is used to evaluate the shear strength of
- Surface concrete
- The bond between carbon fiber reinforced polymer (CFRP) sheets or strips and concrete
- The bond between an overlay and concrete
A disc with an integral ring, 55-mm inner diameter and 75-mm outer diameter, is bonded to the surface using a rapid curing adhesive (GRA) and is used to impart shearing stress to the test surface.
For tests of bare concrete, the surface should be prepared first with a diamond planing tool to produce a flat surface and to expose the coarse aggregate. Before bonding the ring, a special double -barrel coring bit is used to produce partial cores as illustrated below. The coring bit diameters match the inner and outer diameters of the ring.
After the adhesive has cured, a torque is applied to the ring until rupture occurs due to shearing stress. The torque is applied with a special torque housing that is anchored to the surface. The loading is accomplished with the pull machine used for the CAPO-TEST. The load from the pull machine is applied eccentrically to the torque housing, thus producing a torsional moment.
The peak force is recorded and is converted to a shear strength using the provided conversion relationship, as shown above (right).
Additional information can be found in the following reference:
Petersen, C.G. and Poulsen, E., “In-Situ Testing of Near-to-Surface Layer of Concrete and Epoxy-Bonded CFRP Strips,” US-Canada-Europe Workshop on Bridge Engineering, Zürich, Switzerland, 1997.
The coefficient of variation of replicate test results is about 10 % on concrete with a maximum aggregate size of 38 mm.
Testing with the TORQ-TEST on a bridge girder before application of CFRP strips
The TORQ-TEST Equipment and Ordering Numbers
|Torque housing with eccentric loading
|Torque discs, 6 pcs
|GRA glue, box
|Set of anchoring tools, 8 mm
|Anchors, 8 mm, 20 pcs
|Rubber ball dust remover
C-104 CAPO-TEST Pull Machine Kit
|Hydraulic pull machine with electronic gauge,
0-100 kN, 0.1 kN digital division
|AMIGAS printout software
|Cable for printout
|Oil refilling cup
|Oil refilling bottle
The twin drill bit for partial coring (Order # TORQ-950) is used with the CS-75 CORECASE.