The present invention relates to a system for testing and measuring of the bonding strength
between ribbed steel bar and the adherent cement/resin/concrete composite. More
particularly, the system of the present invention is adapted to measure the bond strength
by pull out test of the ribbed bar with cement/resin/concrete composite anchorage.
Advantageously, the present invention is directed to a method for conducting tests for
determination of said bonding strength of ribbed steel bar and the adherent
composite/concrete by applying pulling load of desired magnitude using said apparatus for
determination of strength index corresponding to the bond strength capacity range of the
cement/resin/concrete composite. The system and the method of the invention thus provide
means for determination of the bond strength for a number of applications in structures and
components in construction, rock bolting system and allied application.
BACKGROUND ART
It is known in the related art that testing of construction/precast materials for ensuring
desired integrity and bond response is a critical parameter to consider, particularly for steel
reinforcement and the anchorage material /cast composites /cement. It is also known in
the art that steel ribbed bar are extensively used in RCC Structure as reinforcing elements,
in tunnel construction and underground mines as rock bolt for rockmass stabilization
purpose. These bars form composite with adherents like concrete, resin or cement mix
depending on specific application. The composite action becomes effective when the transfer
of force is maintained between steel and adherent without failure. This force transfer
mechanism is referred to as bond. Bond tests are carried out to determine the strength of
the bond between an adherent and substrate. The strength of the bond is tested by
shearing the adherent from the substrate and measuring the force required to fail the bond.
In case of ribbed steel bar composites, bond response can be evaluated by applying a pull
load on the ribbed bar against the encased adherent as mentioned above and, which is
parallel to the surface of the substrate. There are a few experimental setup/standards in the
related art to determine the bond strength by load slip behavior. IS-2770 Pt. Ill, 1967 pull
test for reinforced concrete; BS 7861 Part I, 1996 double embedment pull test for resin

composite; ASTM F 432, 2004 pull test for strength index of chemical anchorage, provides
some guidelines for the measurement of bond strength but are involving either cost
extensive or complex procedure to carry out the testing and bond strength determination.
There has thus been a persistent need in the art in view of extensive use of ribbed steel bar
as reinforcement for RCC and also for resin or other anchorage in a variety of construction
application, to develop a device/system for measuring bond strength between the ribbed
steel bar and the anchorage material in a simple and accurate manner with less cost and
manpower. The present invention is configured to measure the bond strength by pull out
test of the ribbed bar cement/resin/concrete composite to meet the requirements in the art
and also to overcome the limitations of the existing bond strength measurement systems
and methods.
OBJECTS OF THE INVENTION
Thus according to the basic object of the present invention there is provided a
system/apparatus and accessories for pull out testing and measurement of bond strength of
ribbed steel bar with chemical anchorage or RCC cast specimens including
cement/resin/concrete composite, in terms of strength index corresponding to bond
strength capacity .
Another object of the present invention is directed to developing a methodology of testing
and bond strength measurement of standard specimens using the above mentioned
apparatus/system.
A further object of the present invention is directed to preparing specimen in the form of
threaded steel bar of desired length as well as a steel cylinder to cast the
composite/concrete or grouting materials with the ribbed steel bar of specified size, for
conducting pull out test using the apparatus of the invention.

A still further object of the present invention is thus directed to a system/apparatus and
accessories for pull out testing and measurement of bond strength of ribbed steel bar with
chemical anchorage/concrete wherein tests are conducted to generate data for
determination of strength index with numerical designation ranging from 0 to 15 that
represents the corresponding load range in kN.
A still further object of the present invention is thus directed to a system/apparatus for pull
out testing and measurement of bond strength of grouted ribbed steel bar wherein said pull
out force is applied on to the test specimen by means of a hydraulic jack with hollow
cylinder ram standard accessories like manual hydraulic pump, load gauge (0-600kN) and
dial indicator (0-10mm) etc. to carry out desired precise measurement of strength index in
laboratory scale, adapted for field application for large scale construction.
A still further object of the present invention is thus directed to a system/apparatus for pull
out testing and measurement of bond strength wherein the preparation of test specimens
with grouting materials (adherent) is cured in prescribed manner prior to test.
A still further object of the present invention is thus directed to a system/apparatus for pull
out testing and measurement of bond strength wherein load is applied by means of manual
operation of hydraulic pump to the test section so that the hydraulic ram applies load in
increments of 10 kN, and maximum upto 425 kN load, wherein each increment of load is
stabilized for a period of 1 minute prior to reading the dial indicator and acceptance
standard is limited to movement not exceeding 2.5 mm, the strength index is obtained,
what must be achieved for eighty percent of readings, using a total five samples.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention is thus directed to a system for
determination of bond strength of ribbed bar and anchorage material composites
comprising:

a hollow centered ram adapted to hold the specimen to be tested comprising anchorage
material with the ribbed bar;
manual hydraulic pump operatively connected said hollow centered ram such that by
applying incremental load the movement of the bar is monitored by means of an indicator
meant for desired bar slippage indication and its measurement.
A further aspect of the present invention is directed to a system for determination of bond
strength wherein the hydraulic pump is adapted to apply said incremental load on the
specimen including the grouted ribbed bar to thereby monitor the bar slippage.
A still further aspect of the present invention is directed to a system for determination of
bond strength wherein said dial indicator is adapted to suitably attached to a cut flat top
end of the specimen.
A still further aspect of the present invention is directed to a system for determination of
bond strength comprising connecting pipes with suitable connectors, base plate for dial
gauge holder and a safe protection chamber.
According to yet another aspect of the present invention is directed to a system for
determination of bond strength wherein the hydraulic pump is manually fitted with a
connecting hose and load gauge adapted to measure forces of upto 500kN and said dial
indicator is adapted to measure minimum displacement to one tenth of a millimeter.
A still further aspect of the present invention is directed to said a system for determination
of bond strength comprising fixtures including said hollow centered ram adapted to favour
installation of the test specimen.

Another important aspect of the present invention is directed to a method for the
determination of bond strength of specimens using the system comprising:
preparation of the specimen for testing comprising:
providing a specimen forming cylinder with internal threads ;
pouring the premix of the grout into the cylinder and inserting the bar of sufficient
length to cover the length of the cylinder and also the hydraulic jack and rotating
the bar as per the requirement and allowing the specimen thus formed to curing;
assembling the test section/specimen into the fixture and the hydraulic ram;
attaching a dial indicator to the steel tube to indicate the movement of the bar
slippage on application of load with respect to the cylinder; and
manually applying load using the hydraulic pump to the test section and monitoring
any movement of the bar slippage on application of load with respect to the cylinder.
A still further aspect of the present invention is directed to said method for the
determination of bond strength wherein the load is applied manually to the test section by
means of the hydraulic pump such that the hydraulic ram in increments of lOkN with a
maximum up to 425 kN load, each increment of load being stabilized for a period of one
minute prior to taking reading on the dial indicator.
A still further aspect of the present invention is directed to said method for the
determination of bond strength wherein if the bar movement exceeds 2.5 mm the test is
terminated and minimum of five tests are done and eighty percent should achieve the

strength index to qualify and the strength index comprises a numerical designation ranging
from 0 to 15 representing corresponding load in kN that can be supported by a grouting
material with less than 2.5mm of bar slippage.
According to yet another aspect of the present invention directed to said method for the
determination of bond strength wherein for tests of resin grouted bar the cylinder used
comprises an internal diameter of 5 mm + the diameter of the bar and an outside diameter
of 25mm + diameter of the bar and for cement grouted bar an internal diameter of 20mm +
the diameter of the bar and an outside diameter of 40mm + the diameter of the bar.
A still further aspect of the present invention is directed to said method for the
determination of bond strength wherein for specimen preparation initially the cylinder and
the bar are degreased and all the components are stabilized at a room temperature.
The present invention and its objects and advantages are described in greater details with
reference to the following non limiting illustrative figure.
BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURE
Figure 1: is the schematic illustration of the bond test apparatus/system according to the
present invention to determine bond strength of various test specimens following procedure
mentioned above.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE
ACCOMPANYING FIGURE
The present invention is directed to developing an apparatus/system and method to
measure the bond strength by pull out test of the ribbed bar cement/resin/concrete
composite.
In order to evaluate the bond strength properties of ribbed bar and anchorage materials an
equipment/apparatus has been designed and fabricated. This simple equipment can be
utilized to generate data for determination of strength index. All the required standard
accessories like, manual pump, load gauge (0-600kN), dial indicator (0-10mm), connecting
hose etc are fitted to form a composite system to carry out desired test and measurement
of bond strength. Several tests have been carried out with the developed equipment and
test specimens prepared.
EXAMPLE:
The set up for laboratory test and measuring of the bond strength of grouting materials can
be scaled up to actual field application in large scale construction work for testing in bulk.
The system and method of implementation of the testing and measurement of the bond
strength according to the invention is described with respect to following exemplary
embodiment.
The strength index is a numerical designation ranging from 0 to 15 that represents the
corresponding load in kN, that can be supported by grouting materials with less than 2.5mm
of bar slippage when tested, the index values are presented in the following Table I.


The present method for determination of the strength index as indicator of the bond
strength between the ribbed steel bar and the adherent/chemical anchorage/concrete
involves the following main components and functions:
1. The system for Bond test measurement of strength index comprises an apparatus
such as a hydraulic jack with hollow centered ram adapted to mount the prepared
test sample and for applying desired pull out force on ribbed bar reinforced grouted
sample, manually operating hydraulic pump fitted with a connecting hose and load
gauge that measures force upto 500 kN, a dial indicator that measures minimum
displacement to one hundredth of a millimeter and having a range of l-10mm.
2. The Test Specimen consists of:
a. Plain or ribbed steel bar of length not less than 650mm is taken to
accommodate the hydraulic jack length (400mm) as well as Cylinder
(150mm) length. Around 100mm length at one end of the bar is threaded on

outer diameter of nearest standard metric thread. Other end to be cut flat
and smoothened for convenient attachment to dial indicator.
b. Seam less steel (IS 2062 Gr E 250) cylinder of 150mm length of required
diameter as given in the Table 2 having internally threaded with 1mm pitch is
used for grouting;

c. Adherent materials like resin or cement for which bond tests are conducted:
Materials to be premixed and poured into cylinder. Care should be taken to
ensure that the ribbed bar is fully grouted and void free throughout the length
and placed centrally to the cylinder.
The procedure for conducting the test with specimen and carrying out the bond strength
measurement:
Reference is now invited to the accompanying Figure 1, that illustrates schematically the
apparatus/system for testing and bond strength measurements as strength index for a
number of test specimens following the ASTM procedure for conducting the tests. It is
clearly evident from the test set up as presented in the accompanying Figure 1, that the
following salient inventive features are present in the equipments and method of the
invention:
1. Design of bond test apparatus consists of hollow centered hydraulic jack manual
hydraulic pump fitted with dial indicator for slip measurement, a load gauge for
measurement of applied force and other accessories like connecting pipe with
suitable connectors, base plate for dial gauge holder, and safe protection chamber to
avoidance of accident due to thread failure;
2. Fabrication of test apparatus as per design;
3. Assembly of test apparatus with instruments and checking of functions without
specimen and by applying small load;

4. Preparation of test specimens with grouting materials (adherent) and its curing prior
to test;
5. Preparation of test set up and fixing of test specimen;
6. Conducting actual test following the procedure mentioned above;
7. Repetition of tests and generation of data;
8. Analysis of test data and validation.
It is clearly apparent from the accompanying Figure 1, that the set up comprise a hydraulic
jack with hollow core wherein the test bar with grouting within a cylinder is mounted by
means of bolting, such that when the pressure within the hydraulic cylinder is incrementally
applied the load is applied on to the test specimen. The force so applied is in increment of
10KN and up to a maximum of 425 kN wherein the manually operated load gauge having
capacity of 0-500kN. A dial gauge is so mounted that its stylus touches the ground finished
surface of the ribbed steel bar under testing at the top surface so that on application of load
the slip occurs between metal and adherent beyond certain load limit which is read by the
dial gauge having a range of l-10mm and a LC of 0.1mm to measure desired slip to desired
precision, such that the corresponding strength index is obtained from load applied using
Tablel.
The present invention is directed to preparation of the test set up and conducting the tests
and measurements of the bond strength of the ribbed steel bar reinforced concrete or
chemical anchorage, are carried out.
Preparation of Test Set up and conducting tests/measurements comprising the steps of:
a. Degrease steel tube/cylinder and bar.
b. Stabilize all components at a room temperature.
c. The specimen shall be prepared by placing the grout cartridge into the threaded
tube, inserting the bar and rotating the bar in accordance with the grout
manufacturer's installation instructions.
d. The specimen shall be cured for 24 hrs.
e. Assemble the test section into the fixture and hydraulic ram.
f. Attach the dial indicator to the steel tube to indicate movement of the cut and
finished end of the bar with respect to the tube.

g. Manually apply load by means of hydraulic pump to the test section so that the
hydraulic ram is operated in increments of 10 kN and a Maximum upto 425 kl\l load.
h. Each increment of load shall be stabilized for a period of 1 minute prior to recording
the reading of the dial indicator.
i. If dial gauge reading exceeds 2.5 mm, terminate the test.
j. Minimum of five tests are required. Eighty percent must achieve the desired
strength index.
It is thus possible by way of the present invention to develop a system/apparatus and a
method following the guidelines of relevant ASTM standard directed to desired measurement
of bond strength between the ribbed steel bar and the adherent, comprising the chemical
anchorage or concrete/cement, on the principle of pull out load application. The resultant
measurement of slip along adjacent shear surface is recorded such that the corresponding
application of load is measured as Strength Index using standard Table 1 to ascertain the
bond strength between the ribbed steel bar and the adherent. The present apparatus and
the method of bond strength measurement is thus capable of ensuring reliable test and
precise results for a number of structural /construction/mining/tunneling applications in a
simple and cost effective yet accurate manner.

WE CLAIM:
1. A system for determination of bond strength of ribbed bar and anchorage material
composites comprising:
a hollow centered ram adapted to hold the specimen to be tested comprising
anchorage material with the ribbed bar;
manual hydraulic pump operatively connected said hollow centered ram such that by
applying incremental load the movement of the bar is monitored by means of an
indicator means for desired bar slippage indication and its measurement.
2. A system for determination of bond strength as claimed in claim 1 wherein the
hydraulic pump is adapted to apply said incremental load on the specimen including
the grouted ribbed bar to thereby monitor the bar slippage.
3. A system for determination of bond strength as claimed in anyone of claims 1 or 2
wherein said dial indicator is adapted to suitably attached to a cut flat top end of the
specimen.
4. A system for determination of bond strength as claimed in anyone of claims 1 to 3
comprising connecting pipes with suitable connectors, base plate for dial gauge
holder and a safe protection chamber.
5. A system for determination of bond strength as claimed in anyone of claims 1 to 4
wherein the hydraulic pump is manually fitted with a connecting hose and load gauge
adapted to measure forces of upto 500kN and said dial indicator is adapted to
measure minimum displacement to one tenth of a millimeter.

6. A system for determination of bond strength as claimed in anyone of claims 1 to 5
comprising fixtures including said hollow centered ram adapted to favour installation
of the test specimen.
7. A method for the determination of bond strength of specimens using the system as
claimed in anyone of claims 1 to 6 comprising:
preparation of the specimen for testing comprising:
providing a specimen forming cylinder with internal threads ;
pouring the premix of the grout into the cylinder and inserting the bar of sufficient
length to cover the length of the cylinder and also the hydraulic jack and rotating
the bar as per the requirement and allowing the specimen thus formed to curing;
assembling the test section/specimen into the fixture and the hydraulic ram;
attaching a dial indicator to the steel tube to indicate the movement of the bar
slippage on application of load with respect to the cylinder; and
manually applying load using the hydraulic pump to the test section and monitoring
any bar slippage by movement of the bar slippage on application of load with
respect to the cylinder.
8. A method for the determination of bond strength as claimed in claim 7 wherein the
load is applied manually to the test section by means of the hydraulic pump such
that the hydraulic ram in increments of lOkN with a maximum upto 425kN load,

each increment of load being stabilized for a period of 1 minute prior to taking
reading on the dial indicator.
9. A method for the determination of bond strength as claimed in anyone of claims 7 or
8 wherein if the bar movement exceeds 2.5 mm the test is terminated and minimum
of five tests are done and eighty percent should achieve the strength index to qualify
and the strength index comprises a numerical designation ranging from 0 to 15
representing corresponding load in kN that can be supported by a grouting material
with less than 2.5mm of bar slippage.
10. A method for the determination of bond strength as claimed in anyone of claims 7 or
9 wherein for tests of resin grouted bar the cylinder used comprises an internal
diameter of 5 mm + the diameter of the bar and an outside diameter of 25mm +
diameter of the bar and for cement grouted bar an internal diameter of 20mm + the
diameter of the bar and an outside diameter of 40mm + the diameter of the bar.
11. A method for the determination of bond strength as claimed in anyone of claims 7 or
10 wherein for specimen preparation initially the cylinder and the bar are degreased
and all the components are stabilized at a room temperature.
12. A system for determination of bond strength of ribbed bar and anchorage material
composites and a method for such determination of bond strength of ribbed bar and
anchorage material composites substantially as hereindescribed and illustrated with
reference to the accompanying examples and figures.

This invention is directed to a system involving an apparatus for testing and measuring of
the bonding strength between ribbed steel bar and the adherent cement/resin/concrete
composite. More particularly, the present invention is adapted to measure the bond strength
by pull out test of the ribbed bar with cement/resin/concrete composite anchorage.
Advantageously, the method for conducting tests for determination of said bonding strength
carried out by applying pulling load of desired magnitude using said apparatus for
determination of strength index corresponding to the load bearing capacity with less than
2.5mm of bar slippage when tested. The bond strength is determined in a simple manner as
strength index with numerical designation ranging from 0 to 15, following the guidelines of
ASTM F-432 standard using the system comprising hydraulic jack with hollow centered ram,
manually operated hydraulic pump fitted with a connecting hose, a load gauge that
measures force up to 500 kN, a dial indicator having range 1-10mm and LC 0.1mm, the
ribbed bar grouted test specimen, a test set up.