Basalt Reinforced Concrete

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Nov 29, 2013 (3 years and 4 months ago)

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basalt Reinforced Concrete
-

A POTENTIAL REPLACEMENT FOR STEEL REINFORCED CONCRETE


sponsor: transportation RESEARCH BOARD, National Research Council AND RESEARCH & TECHNOLOGY, INC, MADISON, WISCONSIN.

INNOVATIONS DESERVING EXPLORATORY ANALYSIS (IDEA) PROJECT UNDER GRANT NOS: NCHRP
-

45, 1998 AND NCHRP
-

86,2001


Principal Investigator:

Dr. V. Ramakrishnan

Project Monitor:

Dr. Inam Jawed, TRB

Research Engineer:

Vladimir B. Brik, RTC, Inc.


Graduate Research Assistants:
Rajesh Kumar N, Ramesh Panchalan and Srinivas Sathyanarayan




PROBLEM STATEMENT



The

innovative

aspect

of

this

project

is

the

detailed

study

of

non
-
corrosive,

basalt

fiber

composite

rebar
.


This

rebar

consists

of

80
%

fibers

and

has

a

tensile

strength

three

times

that

of

the

steel

bar
.

It

is

made,

by

utilizing

a

resin

(epoxy)

binder
.


Basalt

fiber

composite

rebars

have

the

potential

to

replace

steel

in

reinforced

concrete

structures

exposed

to

salt

water,

ocean

climate,

etc
.

wherever

the

corrosion

problem

exists
.



The

basalt

rock

required

for

manufacturing

basalt

fibers

is

abundantly

available

all

over

the

world

and

hence

can

prove

to

be

an

easy

source,

thus

reducing

the

production

costs
.


Basalt

rebar

has

one
-
third

of

the

weight

of

steel

and

the

thermal

expansion

coefficient

is

very

close

to

that

of

concrete
.


The

high

mechanical

performance/price

ratio

of

basalt

fiber

composite

rebar,

combined

with

corrosion

resistance

to

alkaline

attack

are

further

reasons,

for

replacing

steel

in

concrete

by

basalt

fiber

composite

rebar
.


OBJECTIVES

This

investigation

was

undertaken

to

evaluate

the

performance

of

concrete

reinforced

with

basalt

fiber

composite

rebars
.


The

following

were

the

objectives

of

the

research
.


To

determine

the

ultimate

failing

load
.


To

study

the

load
-
deflection

behavior
.


To

observe

the

bond

strength
.


To

measure

the

strain

in

the

concrete
.


To

study

the

mode

of

the

failure
.

TENSION TEST ON THE ROD


The tension test was done on basalt bars, with 14.25mm and 6mm
diameters and also on a cable, 6mm diameter, and the ultimate tensile
strength was found to be 1458 MPa, 707.5 MPa and 308 Mpa
respectively.


The bars experienced a brittle type of failure with splintering of fibers.


The cable broke into two pieces without any splintering of the fibers,
unlike both the bars.

PROPERTIES OF BASALT FIBERS


A

unique

process

of

producing

continuous

amorphous

basalt

fibers

had

been

developed

in

the

Ukraine
.

These

fibers

have

exceptional

strength

and

stiffness
.



During

high

speed

spinning

attenuation,

these

fibers

are

braided

into

roving

containing

about

200

elemental

fibers
.

Basalt

fibers

exhibit

a

high

level

of

mechanical

characteristics

(tensile

strength,

modulus)

and

chemical

stability

in

cement

media
.



The

tensile

strength

of

continuous

basalt

fibers

is

about

twice

that

of

E
-
glass

fibers

and

the

modulus

of

elasticity

is

about

15
-
30
%

higher
.

They

possess

high

heat

stability

and

insulating

characteristics

and

have

an

elastic

structure
.

They

can

be

easily

processed

into

fabric

with

high

reliability
.


The

chemical

stability

of

basalt

fibers

in

cement

and

alkaline

media

is

higher

than

that

of

E
-
glass

fibers
.

Basalt

fibers

in

an

amorphous

state

exhibit

higher

chemical

stability

than

glass

fibers
.

When

exposed

to

water

at

70


C

(
158


F),

basalt

fibers

maintain

their

strength

for

1200

hrs,

whereas

the

glass

fibers

do

so

only

for

200

hrs
.

RESULTS AND DISCUSSIONS
RESULTS AND DISCUSSIONS
BEAMS DESIGNED AND BUILT IN THE LAB
BEAMS DESIGNED AND BUILT IN THE LAB

Six beams were designed and cast in the lab for the investigatio
n. The
beams were tested in bending after 14
-
day curing period. The beams
failed with a single crack instead of multiple cracking, which i
ndicated
slip of the reinforcing bars.

After the testing was done the beams edges were cut using a diam
ond
tipped saw.

The slip of the basalt bar was clearly visible at both the ends
with a
distinct mark left in the concrete at the original placing of th
e
reinforcement.

The overall test results indicate that there was insufficient bo
nd
strength and the bars slipped gradually before the ultimate load
was
reached.

Two beams were tested with increased development lengths. One
beam failed in flexure, but at a higher load than other beams du
e to
the increased development length, whereas another beam failed
suddenly with the breaking of the reinforcement. It was a sudden
and
brittle failure.
RESULTS AND DISCUSSIONS
RESULTS AND DISCUSSIONS
BEAMS SUPPLIED BY THE MANUFACTURER
BEAMS SUPPLIED BY THE MANUFACTURER

Research & Technology Inc. supplied 8 beams. Five beams (BRC
-
1 to
5) were reinforced with basalt fiber composite rebars. Four of t
hese
beams had 3
-
D basalt fiber reinforced concrete. Three beams (P1 to
P3) were plain concrete (control) beams.

All the beams were tested in bending and the deflections were
measured.

The ASTM toughness indices, Japanese toughness indices, and the
Equivalent flexural strengths were calculated. Beams with 3D
-
basalt
fiber reinforced concrete had a ductile failure.

One Beam without 3D fibers, and reinforced with only rebars had
a
gradual brittle failure after considerable deflection, due to bo
nd failure
between the basalt rebar and concrete matrix.

All three plain concrete beams without any 3D
-
fibers and basalt
rebars, failed instantaneously, at the appearance of the first c
rack. The
failure was brittle and sudden.

The addition of reinforcement, either in the form of small fiber
s or
composite basalt rods converted the brittle failure into a ducti
le
failure.
BOND TEST ON BASALT REBARS
BOND TEST ON BASALT REBARS
objective
objective

To improve the performance of basalt reinforced concrete it was
necessary to increase the bond strength of the rebars by providi
ng
some slots (modulations on the surface).

The bond tests were done on basalt rebars according to the proce
dures
of ASTM C 234. The rebars used were plain basalt rods, 4

slot
rebars, and 8

slot rebars.
TEST RESULTS
TEST RESULTS

As the load was applied the plain basalt rebars started slipping
after
sometime and there was no bond between the reinforcement and the
concrete.

The 4
-
slot basalt bar was tested for both the lower and upper
horizontal position of the reinforcement. The 4
-
slot basalt bar did not
slip and hence there was no bond failure. But the basalt bar its
elf
failed due to tension failure (rather than slip) indicating good
bond
strength. The 8
-
slot basalt bar behaved in the same way as the 4
-
slot
bar.

The plot between the bond stress and slip were plotted for all t
he
specimens reinforced with different types of basalt bars for bot
h the
lower and the upper horizontal positions of the basalt rebars.
CONCLUSIONS
CONCLUSIONS

The beams that were designed and cast in the laboratory failed i
n
flexure due to inadequate bond.

The beams supplied by the manufacturer reinforced with
3D
-
fibers and
rebars exhibited a primary failure in flexure and shear, followe
d by a
secondary failure in splitting.

The 3D
-
fibers caused a ductile failure of the beam and also increased
the actual cracking moment capacity of the beam.

All the actual ultimate moments were much less than the calculat
ed
ultimate moments due to bar pullout failure. All the beams were
tested
in bending and the deflections were measured.

The bond between the basalt rebar and the concrete matrix should
be
increased by roughening the bar or having modulations on the sur
face,
to increase the actual ultimate load carrying capacity of the be
am.

The slots provided on the basalt rebars increased the bond stren
gth
considerably, thus eliminating the major deficiency of the basal
t rebar
reinforced concrete as potential replacement to steel reinforced
concrete.
Beam
Dimensions
Details of Reinforcement
No.
(in)
BRC-A
12in x 12in x 51in
Two basalt rebars with a diameter of 0.56in
and length 48in. The cover was maintained at
1in. Development length was 4.5in on each side.
BRC-B
10in x 10in x 51in
Two basalt rebars with a diameter of 0.56in
and length 48in. The cover was maintained at
1 in. Development length was 4.5in on each side.
BRC-C
12in x 12in x 51in
Two basalt rebars with a diameter of 0.56in
and length 48in. The cover was maintained at
3.5 in. Development length was 4.5in on each side.
BRC-D
10in x 10in x 51in
Two basalt rebars with a diameter of 0.56in
and length 48in. The cover was maintained at
3.25 in. Development length was 4.5in on each side.
BRC-E
6in x 6in x 51in
Two basalt rebars with a diameter of 0.56in
and length 48in. The cover was maintained at 1in.
Development length was 12in on each side.
BRC-F
6in x 6in x 66in
Two basalt rebars with a diameter of 0.2in
and length 60in. The cover was maintained at 1in.
Development length was 15in on each side.
Details of Beams Designed and Cast in the Lab
Name
Size of
No
Coarse
Beam
of
Fibers
(inches)
Bars
(%)
BRC-1
3in x 4in x 14in
5
2 rods with 6.75mm(0.265in) in diameter(top) & 1
1.5
rod having periodical twisted ribs & made from 2
cables of 3mm(0.118in) diameter & 2 rods with
6.75mm(0.27in) in diameter at bottom.
BRC-2
3in x 4in x 14in
5
2 rods with 6.75mm(0.265in) in
2
diameter(top) & 1 rod 8mm(0.32in) in diameter
& 2 rods with 6.75mm(0.27in)diameter at bottom.
BRC-3
3in x 4in x 14in
5
2 rods with 6.75mm(0.265in) in diameter(top)
1.5
& 1 rod having periodical twisted ribs & made
from 2 cables of 3mm(0.118in) diameter & 2 rods
with 6.75mm(0.27in) at bottom.
BRC-4
3in x 4in x 14in
5
2 rods with 6.75mm(0.265in) in diameter(top)
--
& 1 rod having periodical twisted ribs
& made from 2 cables of 3mm(0.118in) diameter
with 2 rods of 8mm(0.32in) diameter at bottom.
BRC-5
3in x 4in x 14in
4
2 rods at top with 6mm(0.24in) in diameter & 2 rods
2
at bottom with 6mm(0.24in) in diameter. Fibers
were ROVING RB-15(chopped) & 10mm(0.4in) in
length.
Details of Beams Supplied by the Manufacturer
Description of Bars
Beam
Ultimate
Cracking
No.
Load
Load
Ultimate
Cracking
Ultimate
Cracking
KN(lbs)
KN(lbs)
KN.m(k-ft.)
KN.m(k-ft.)
KN.m(k-ft.)
KN.m(k-ft.)
BRC-A
71.20
66.00
19.04
17.65
118.90
17.00
(16000)
(15000)
(14.04)
(13.00)
(87.70)
(13.90)
BRC-B
44.50
37.80
11.90
10.11
102.02
9.49
(10000)
(8500)
(8.77)
(7.45)
(75.23)
(7.00)
BRC-C
68.50
57.80
18.30
15.50
89.40
17.00
(15400)
(13000)
(13.51)
(11.40)
(659.00)
(13.90)
BRC-D
43.00
35.60
11.50
9.50
65.52
9.50
(9700)
(8000)
(8.50)
(7.02)
(48.30)
(7.00)
BRC-E
45.00
40.00
8.50
7.62
35.90
2.20
(10100)
(9000)
(6.32)
(5.60)
(26.50)
(1.62)
BRC-F
12.20
11.10
3.26
2.96
3.50
2.20
(2750)
(2500)
(2.60)
(2.20)
(2.60)
(1.62)
Actual Moments
Calculated Moments
Comparison of Calculated & Actual Moments
(Beams Cast in the Lab: BRC-A to F)
Beam
Ultimate
Cracking
No.
Load
Load
Ultimate
Cracking
Ultimate
Cracking
(KN)
(KN)
(KN.m)
(KN.m)
(KN.m)
(KN.m)
BRC-1
20.00
17.70
1.77
1.60
4.07
0.32
BRC-2
18.20
16.00
1.60
1.42
4.30
0.32
BRC-3
15.60
12.40
1.40
1.10
4.07
0.32
BRC-4
21.00
19.00
1.90
1.70
5.50
0.32
BRC-5
16.00
15.00
1.42
1.33
3.20
0.32
Comparison of Calculated and Actual Moments of Beams
(BRC 1-5) Supplied by the Manufacturer
Calculated Moments
Actual Moments
Comparison of Bond Stress vs. Slip for all types of
Reinforcements
-
Upper Horizontal Position
0
200
400
600
800
1000
1200
1400
1600
1800
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Slip (in.)
Bond Stress (psi)
4
-
Slot Basalt Bar
8
-
Slot Basalt Bar
Plain Basalt Bar
Steel Reinforcement
TEST SET
UP
Comparison of Bond Stress vs. Slip for all types of
Reinforcements
-
Upper Horizontal Position
0
200
400
600
800
1000
1200
1400
1600
1800
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Slip (in.)
Bond Stress (psi)
4
-
Slot Basalt Bar
8
-
Slot Basalt Bar
Plain Basalt Bar
Steel Reinforcement
Comparison of Bond Stress vs. Slip for all types of
Reinforcements
-
Upper Horizontal Position
0
200
400
600
800
1000
1200
1400
1600
1800
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
Slip (in.)
Bond Stress (psi)
4
-
Slot Basalt Bar
8
-
Slot Basalt Bar
Plain Basalt Bar
Steel Reinforcement
TEST SET
UP
Basalt Rod before and after failure
Basalt Rod before and after failure
Basalt Rod before and after failure
Basalt Rod before and after failure
Failed Specimens
Failed Specimens
RESEARCH PROGRAM
RESEARCH PROGRAM

A total of eleven beams reinforced with basalt rebars were
teste
Research & Technology Inc supplied five beams and six beams were
designed and cast in the lab.

The beams that were designed and cast in the lab are referred to
BRC
-
A to F in the discussion whereas the beams supplied by the
manufacturer are referred to as BRC
-
1 to 5.

Three plain concrete (control) beams were also supplied which
ar
referred to as P1
-
3.
Failed Specimens
Failed Specimens
RESEARCH PROGRAM
RESEARCH PROGRAM

A total of eleven beams reinforced with basalt rebars were teste
d.
Research & Technology Inc supplied five beams and six beams were
designed and cast in the lab.

The beams that were designed and cast in the lab are referred to
as
BRC
-
A to F in the discussion whereas the beams supplied by the
manufacturer are referred to as BRC
-
1 to 5.

Three plain concrete (control) beams were also supplied which ar
e
referred to as P1
-
3.
Failed Specimens
Failed Specimens
RESEARCH PROGRAM
RESEARCH PROGRAM

A total of eleven beams reinforced with basalt rebars were
teste
Research & Technology Inc supplied five beams and six beams were
designed and cast in the lab.

The beams that were designed and cast in the lab are referred to
BRC
-
A to F in the discussion whereas the beams supplied by the
manufacturer are referred to as BRC
-
1 to 5.

Three plain concrete (control) beams were also supplied which
ar
referred to as P1
-
3.
Failed Specimens
Failed Specimens
RESEARCH PROGRAM
RESEARCH PROGRAM

A total of eleven beams reinforced with basalt rebars were teste
d.
Research & Technology Inc supplied five beams and six beams were
designed and cast in the lab.

The beams that were designed and cast in the lab are referred to
as
BRC
-
A to F in the discussion whereas the beams supplied by the
manufacturer are referred to as BRC
-
1 to 5.

Three plain concrete (control) beams were also supplied which ar
e
referred to as P1
-
3.
TEST SET
UP OF BASALT REINFORCED CONCRETE BEAMS
CAST IN THE LAB WITH DATA ACQUISITION SOFTWARE
TEST SET
UP OF BASALT REINFORCED CONCRETE BEAMS
CAST IN THE LAB WITH DATA ACQUISITION SOFTWARE
TEST SET
UP OF BASALT REINFORCED CONCRETE BEAMS
CAST IN THE LAB WITH ELECTRICAL STRAIN GAUGES
TEST SET
UP OF BASALT REINFORCED CONCRETE BEAMS
CAST IN THE LAB WITH ELECTRICAL STRAIN GAUGES
CLOSE
UP OF BEAM AFTER FAILURE: A SINGLE
CRACK INSTEAD OF MULTIPLE CRACKING CAUSED
THE FAILURE INDICATING BOND SLIP
CLOSE
UP OF BEAM AFTER FAILURE: A SINGLE
CRACK INSTEAD OF MULTIPLE CRACKING CAUSED
THE FAILURE INDICATING BOND SLIP
CLOSE
UP OF CRACKED BASALT REINFORCED CONCRETE
BEAM CAST IN THE LAB STILL CARRYING MAXIMUM LOAD
CLOSE
UP OF CRACKED BASALT REINFORCED CONCRETE
BEAM CAST IN THE LAB STILL CARRYING MAXIMUM LOAD
CLOSE
UP OF SLIP OF REINFORCEMENT
CLOSE
UP OF SLIP OF REINFORCEMENT
SLIP OF REINFORCEMENT AT LEFT END
OF BEAM
SLIP OF REINFORCEMENT AT LEFT END
OF BEAM
TEST SET
UP OF BEAM (SUPPLIED BY THE
MANUFACTURER) WITH TRUE DEFLECTION MEASURING
FRAME AND ELECTRICAL STRAIN GAUGE WIRE
TEST SET
UP OF BEAM (SUPPLIED BY THE
MANUFACTURER) WITH TRUE DEFLECTION MEASURING
FRAME AND ELECTRICAL STRAIN GAUGE WIRE
TEST SET
UP FOR TRUE DEFLECTION MEASUREMENT
OF BEAMS SUPPLIED BY THE MANUFACTURER
TEST SET
UP FOR TRUE DEFLECTION MEASUREMENT
OF BEAMS SUPPLIED BY THE MANUFACTURER
CLOSE
UP OF SHEAR MODE OF FAILURE OF BASALT REINFORCED
CONCRETE BEAMS (SUPPLIED BY THE MANUFACTURER)
CLOSE
UP OF SHEAR MODE OF FAILURE OF BASALT REINFORCED
CONCRETE BEAMS (SUPPLIED BY THE MANUFACTURER)
CLOSE
UP OF FLEXURAL MODE OF FAILURE OF BASALT
REINFORCED CONCRETE BEAMS (SUPPLIED BY THE
MANUFACTURER)
CLOSE
UP OF FLEXURAL MODE OF FAILURE OF BASALT
REINFORCED CONCRETE BEAMS (SUPPLIED BY THE
MANUFACTURER)