BOND-TEST.pdf

BOND-TEST

Purpose

The BOND-TEST is used to conduct a pull-off test in accordance with ASTM C 1583, Test Method

for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete

Repair and Overlay Materials by Direct Tension (Pull-off Method). The obtained pull-off strength

can be used for the following purposes:

To evaluate the in-place bond strength between a repair overlay and the substrate

To evaluate the in-place tensile strength of concrete or other materials

To evaluate the effect of surface preparation procedures on the tensile strength of the substrate

before applying a repair material or overlay

To estimate the in-place compressive strength of surface concrete using the following

approximate relationship between tensile streng th f t (MPa) and compressive strength f c (MPa):

f =

Principle

In the BOND-TEST , a disc is bonded to a prepared testing surface and the disc is pulled off after a

partial core has been cut around the disc (extreme left in following figure). The pull-off force, F, is

divided by the cross-sectional area of the partial core to obtain the pull-off strength f p :

where d is the diameter of the partial core.

BOND-TEST (a) Failure in substrate (b) Bond failure (c) Failure in overlay

The types of failures that can occur in a BOND-TEST are illustrated above. Failure in the substrate

(a) indicates that the bond strength is greater than the tensile strength of the substrate. A failure at

the interface (b) provides a measure of the tensile bond strength between the overlay and the

substrate. A failure in the overlay (c) indicates that the bond strength is greater than the tensile

strength of the overlay.

Failure type (a) is the preferred one, as it shows that the bond strength of the overlay is greater than

the tensile strength of the substrate. Note that failure occurs at the weakest link of the composite

system, and one cannot presume beforehand which type of failure will occur.

The nature of the BOND-TEST has been investigated by finite element analyses (see Petersen,

C.G., Dahlblom, O. and Worters, P., ÑBond-Test of Concrete and Overlays,Ò Proceedings,

International Conference on NDT in Civil Engineering, University of Liverpool, U.K., 1997). Failure

in the BOND-TEST using a 75-mm disc was predicted to occur at a displacement of 0.02 mm to 0.03

mm and the nominal stress in the partial core prior to rupture is about 3 % lower than the uniaxial

tensile strength of the substrate concrete.

BOND-TEST

Variability

For 75-mm discs, the coefficient of variation of replicate test results is about 8 to 10 % on concrete

with a maximum aggregate size of 38 mm. For 50-mm discs, the coefficient of variation is 14 to 16 %.

The BOND-TEST procedure

Electric drill

1. Surface planing

The surface is ground with a diamond wheel to

expose the aggregates and to obtain a plane

surface. The center knob is removed with a

separate grinder. The dry surface is steel

brushed and any dust or powder is blown away.

The suction plate is used to control the planing

operation.

Diamond planing

wheel unit

Suction plate

Vacuum

2. Bonding the disc

A clean disc is bonded to the prepared surface

using a rapid-curing adhesive (GRA). The GRA

adhesive has a tensile strength of 10 MPa when

fully cured, which takes 2 to 5 minutes at normal

temperatures. The progress of hardening is

observed in the pot in which the two-component

GRA was mixed. In cold weather conditions, the

concrete surface and the disc are heated with a

heat gun to accelerate curing of the adhesive.

Centering plate

Vacuum

75-mm dia.

disc

3. Partial coring

A partial core is cut perpendicular to the surface;

the bonded disc serves as a drill guide (the inner

diameter of the coring bit fits the disc diameter).

The partial core is cut with the CORECASE (pg.

72). For tests to measure bond strength, the core

is cut to a depth of 25 mm into the substrate or

one-half of the core diameter, whichever is

greater; for tensile strength of the substrate, cut

to a depth of 25 mm.

To spindle assembly

and drill

Water in

Corecase

housing

Waste

water out

Vacuum

4. Pull-off

The disc is loaded in direct tension at a

controlled rate using a calibrated hydraulic pull

machine. The machine bears against a circular

counter pressure ring positioned centrally on the

planed surface. The peak force in kN is recorded

and used to obtain the pull-off strength by

dividing by the cross-sectional area of the partial

core. The type of failure, (a), (b) or (c), as shown

on the previous page, is documented.

Pull off load

measured by gage

Bearing ring of pull

machine

Pull bolt w/

spherical

end

Centering

disc

Counter pressure

ring

The procedure and the special equipment used for the BOND-TEST ensure that the disc is loaded in

direct tension without bending forces. Such bending forces are detrimental and may lower the

results by 20 to 50 %. The discs used (75 mm or 50 mm in diameter) have sufficient stiffness to avoid

distorting during pull-off. By bonding a clean disc on a planed, dry surface with the GRA adhesive,

failure will not occur at the disc/overlay interface, which is an invalid test and must be repeated.

BOND-TEST

Testing Examples

BOND-TEST being performed for quality control of the bond between a wear resistant overlay and a concrete

slab; coring after bonding the 75- mm disc is shown (left), application of pull-off load (middle), and the bond

failure, type (b), between the overlay and the substrate (right) at 1.8 MPa

BOND-TEST being performed on granite

tiles in a subway station

The bond of a repair on a balcony being

evaluated with BOND-TEST

BOND-TEST

The BOND-TEST Equipment and Ordering Numbers

B-10000 DSV-Kit: For surface grinding, bonding the disc, and

attaching the coring rig to produce the partial core without anchoring.

Item

Order #

Diamond planing wheel unit

B-10010

Suction plate with valve and gauge

B-10020

Two adjustable clamping pliers

B-10030

Centering plate for 75 mm disc

Optionally, centering plate for 50 mm disc

B-10040

B-10050

Vacuum pump with hose

B-10060

Wrench, 17 mm

B-10070

Small screwdriver

B-10080

Attach case

B-10090

B-11000 BOND-TEST Preparation Kit: For removing the center

knob after surface grinding, cleaning the surface, bonding the discs,

and heating the discs in cold weather conditions

Item

Order #

Grinder with cup stone

B-11010

Heat gun

B-11020

Steel brush

B-11030

75 mm discs, 6 pcs

Optionally, 50 mm discs, 6 pcs

B-11040

B-11050

GRA glue, box

B-11060

Putty knife

B-11070

Araldite epoxy (for acrylic-based materials)

B-11080

Attach case

B-11090

Optionally:

GRA glue, can with đ kg powder

B-11100

GRA liquid, bottle with 200 mL

B11110

CORECASE CS-75: For producing the partial core.

Item

Order #

Coring rig with coupling

CC-10

Handles for coring rig, 3 pcs

CC-20

Coring bit, 75 mm x 110 mm

CCB-75/110

Water pump with 2 hoses

CC-30

Clamping pliers, adjustable, 2 pcs

CC-40

Set of anchoring tools, 8 mm

CC-50

8 mm expansion anchors, 20

CC-60

Chisel

CC-70

Hammer

CC-80

Corelifter, 75 mm in diameter

CC-90

Wrench, 14 mm

CC-100

Measuring tape

CC-110

Set of spare bearings for coring rig

CC-120

Reinforcement locator

CC-130

Manual

CC-140

Attach case

CC-150

BOND-TEST

Three alternative hydraulic pull machines are available for conducting the BOND-TEST :

B-12000 BOND-TEST Pull Machine Kit

Item

Order #

The hydraulic pull machine

comes with a 0 to 25 kN

analog dial gauge, with 0.5

kN least division. The pull

machine needs to be re-

calibrated once a year, or

sooner, if it is serviced or

damaged. The L-30

calibration unit on page 42

may be used for calibration

Hydraulic pull machine

with analog gauge

B-12010

Centering piece

B-12020

Coupling

L-16

Pull bolt

L-17

Bolt handle

L-19

Oil refilling cup

L-24

Oil refilling bottle

L-25

Large screwdriver

C-149

Small screwdriver

C-157

Calibration table

B-12030

Manual

B-12040

Attach case

B-12050

B-13000 BOND-TEST Pull Machine Kit

Item

Order #

The hydraulic pull machine

has a 0 to100 kN precision

electronic gauge with memory

for storage of test results

(peak-value, time and date of

testing). The peak-value is

shown after a test has been

completed. The internal

accuracy of the gauge is 0.01

kN. The display shows the

pull force in 0.1 kN digital

increments. The pull machine

needs to be re-calibrated once

a year, or sooner, if serviced

or damaged.

Hydraulic pull machine

with electronic gauge

B-13010

AMIGAS printout software L-13

Cable for printout

L-14

Centering piece

B-12020

Coupling

L-16

Pull bolt

L-17

Bolt handle

L-19

Oil refilling cup

L-24

Oil refilling bottle

L-25

Large screwdriver

C-149

Small screwdriver

C-157

Calibration table

B-13030

Manual

B-13040

Attach case

B-13050

B-14000 BOND-TEST Pull Machine Kit

Item

Order #

The hydraulic pull machine

has an automatic loading rate

control and a 0 to 100 kN

precision electronic gauge

with memory for storage of

test results (peak-value, time

and date of testing). The

peak-value is shown after a

test has been completed. The

internal accuracy of the

gauge is 0.01 kN. The display

shows the pull force in 0.1 kN

digital increments. The pull

machine needs to be re-

calibrated once a year, or

sooner, if serviced or

damaged.

Hydraulic pull machine

with electronic gauge

B-14010

AMIGAS printout software L-13

Cable for printout

L-14

Centering piece

B-12020

Coupling

L-16

Pull bolt

L-17

Bolt handle

L-19

Oil refilling cup

L-24

Oil refilling bottle

L-25

Large screwdriver

C-149

Small screwdriver

C-157

Calibration table

B-14030

Manual

B-14040

Attach case

B-14050

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