Abstract: (12591 Views)
This paper introduces an innovative partially destructive method, called “Twist-off”, for
the assessment of in situ concrete strength. In this method a 40mm diameter metal probe is bonded
to a concrete surface by means of a high strength epoxy resin adhesive. To measure the concrete
compressive strength, a torque is applied using an ordinary torque-meter and the maximum shear
stress at failure is used to estimate the cube compressive strength by means of a calibration graph.
The relationship between the results of this new method and compressive strengths of concrete cores
is also presented in this paper. The average coefficient of variation of the results of this method was
seen to be of the order of 8 percent and the correlation coefficients of its comparative results with
concrete cube and core compressive strengths were found to be 0.97 and 0.90 respectively. In order
to assess the performance of this method on site, tests were undertaken on a number of buildings.
Although the method was found to perform well but with some of the structures tested, the
differences between the strengths of sample cubes and estimated in situ compressive strength of
concrete were seen to be significant.
Type of Study:
Technical Note |