Available via license: CC BY-NC-ND 3.0
Content may be subject to copyright.
Procedia Engineering 51 ( 2013 ) 55 – 64
1877-7058 © 2013 The Authors. Published by Elsevier Ltd.
Selection and peer-review under responsibility of Institute of Technology, Nirma University, Ahmedabad.
doi: 10.1016/j.proeng.2013.01.011
“Chemical, Civil and Mechani
c
Conference on Engineering.
Structural Repair and R
e
Buildings, at ONGC colon
y
1.Chief Engineer (Civil), ONGC, Ava
n
Abstract
Although reinforced concrete st
ru
always taken during constructio
n
some times less than 10 years
o
paper, a case study of 3 no. (G+
8
(India) earthquake of 2001, re
h
removal of delaminated carbo
n
coating, polymer bond coat, po
beam-column junctions and cr
a
grouting with SBR modified ce
m
material testing was carried ou
t
were selected for durable rep
workmanship was adopted. Aft
e
of distress in the form of cracks
requiring rehabilitation again.
S
concrete constructions and reha
b
Key words- spalls, delaminatio
n
SBR polymer
1. INTRODUCTION
Concrete is the most versatile m
take any shape but it has certai
n
old and hardened concrete to
n
p
ermeability, shrinkage etc. Du
e
in the form of cracks, spalls, del
a
of concrete, corrosion of reinf
o
aggregate reactions etc. Ingres
s
various forms of chemically
constitutions. The resistance of
p
orosity, the cement compositi
o
hardened. In such circumstance
s
followed by repair and rehabili
t
c
al Engineering Tracks of the 3
rd
Nirma Univ
e
(NUiCONE 2012)
e
habilitation of 3 no. (G+8) Multi-
S
to
r
y
at Chandkheda, Ahmedabad, Gujra
Varinder . K. Singh
1
n
i Bhavan, Chandkheda, Ahmedabad, Gujrat-38242
4
r
uctures are designed as per codes / standards
b
n
process. As a result, the structures start sho
w
o
f service life, requiring early repair and rehab
i
8
) multi-storeyed buildings badly damaged due
t
h
abilitated in 2003 has been presented. Rep
a
n
ated concrete cover , application of rust re
m
lymer modified mortar , injection of low visc
a
cks, repair of masonry cracks with polyme
r
m
ent grout and jacketing of columns at the gr
o
t
and specifications for acrylic and SBR poly
m
airs. St
r
ict quality control and assurance b
o
r nine years of successful rehabilitation and fu
n
and spalls due to rebar corrosion have been no
t
S
ome recommendations /conclusions have be
e
b
ilitation work.
n
, carbonation, corrosion, non- destructive test
an made building material of the recent past be
n
limitations like lower flexural, tensile strengt
h
n
ew and fresh concrete, poor resistance to ch
e
e
to these limitations the concrete structures sta
r
a
minations and ultimate complete collapse as a
o
rcement due to moisture penetration, chlori
d
s
of dissolved substance from the external en
v
induced deterioration by reaction with ce
m
concrete to chemical attack is in general dire
c
o
n used in the concrete and condition under
s
, proper evaluation of damage by visual and
t
ation using construction chemicals which are
e
rsity International
r
eyed residential
t.
4
,India
b
ut enough care is not
w
ing signs of distress,
i
litation work. In this
t
o corrosion and Bhuj
a
ir strategy involved
m
over, anti-corrosion
osity epoxy grout to
r
modified mortar &
o
und floor. Extensive
m
er modified mortar
o
th in material and
n
ctioning, some signs
t
ed at some locations,
e
n given for durable
ing, acrylic polymer,
cause of its ability to
h
, poor bond between
e
micals, porosity and
r
ts showing distresses
result of carbonation
d
e attack, and alkali-
v
ironment may cause
m
ent paste aggregate
c
tly influenced by its
which cement paste
non-destructive tests
superior to ordinary
Available online at www.sciencedirect.com
56 Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
study of three no. (G+8) multi-storeyed residential buildings, badly damaged due to corrosion and
Bhuj (India) earthquake of 2001, repaired and rehabilitated in 2003 has been presented.
In Ahmedabad Asset of ONGC, three no. multi-storeyed (G+8) buildings viz. Heera ( C3), Panna
(B5) and Ratna (B6) each having 68 quarters with half G.F as parking were constructed in year
1989-1990. These buildings were already sick due to severe reinforcement corrosion as evident from
so many spalls, delaminations on column corners located at different heights, beam/ fin soffits, slab
soffits, leached plaster on parapets corroded and leaking drainage pipes, water supply lines and
stagnated water on terraces due to improper gradient etc. These were further damaged by the Bhuj
earthquake on 26
th
Jan, 2001 in the form of separation cracks at beam-column junctions, RCC-
masonry wall interfaces (Fig 6), cracks in masonry in-fills(Fig 5); even complete crumbling at some
places, heavy de-bonding and dismantling of plaster at both exterior and interior surfaces etc. Due to
fast deterioration, it was decided to rehabilitate these buildings at the earliest.
2. PRELIMINARY INVESTIGATION
Visual inspection of the buildings indicated heavy rebar corrosion as a result of carbonation
due to environmental attacks. At certain locations of beams, columns, fins and slabs concrete
cover had got spalled (Fig 3) and some shear stirrups were totally eaten up by corrosion (Fig1).
Beam - column junctions were badly cracked (Fig 2). Some masonry walls at GF level were
totally cracked due to earthquake. A number of columns had continuous vertical cracks along
the line of concrete cover thickness (Fig 4). The visual inspection necessitated the need for
detailed evaluation for design of the rehabilitation design.
Fig.1 De-lamination of beam concrete cover due to rebar corrosion. Fig.2- Severe corrosion and spalling of beam –
column junction due to poor workmanship and in-adequate cover at GF level.
Fig.3 De-lamination of concrete cover due to severe corrosion of rebars of roof slab. Fig. 4-Continuous wide
crack in column due to corrosion of longitudinal steel at concrete cover depth.
3. DETAILED INVESTIGATION
3.1 REBOUND HAMMER TEST:
Rebound hammer test was carried out at different points to access the
strength of the structural elements. Rebound numbers were determined after exposing the concrete
surface by removing plaster and removing slurry and by taking at least five readings at a point and
57
Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
averaging them the results showed that compressive strength in columns and beams varied from
11.2 N/mm
2
to 32.6 N/mm
2.
3.2 CORE TEST: Three no. core Tests were also carried out one in each building (Table 1). The
results obtained were –
Table 1. Core test results
3.3 ULTRA SOUND PULSE VELOCITY TEST
The USPV Test was carried out on 34 nos of columns and 6 nos beams and the results obtained are -
3.3.1 COLUMNS
In general, the tests on columns showed good quality of concrete. Out of 34 columns, 28 columns
(about 82%) mean observation showed good quality of concrete, 3 (about 9%) showed doubtful
quality and 3no.columns showed fair quality of concrete. In all columns including those of good
quality category, the quality of concrete either near the junction with the beams or near the floor or
both had spots of relatively lower value of USPV.
The test results showed that consistency of inferred quality was low. Observations in 7 columns of
28 good quality columns were having high (more than 10%) value of coefficient of variation (CV).
In fair and doubtful quality columns, the inconsistency was poorer. This means that the quality of
concrete was erratic in general. Only 25% of columns showed consistent quality (CV <5%). This
means that barring those columns with CV < 5%, rest columns have patches of variable quality of
concrete in general. The range of Pulse velocity ranges from low value of 2320 m/sec. in col.C21 in
B6 Panna Block to high value of 4333 m/s for columns C-230 in the same block. In Block B5 Ratna,
the variation range from 3757 m/s to 4112 m/sec. with all having doubtful junction. Heera building
had more columns with doubtful and fair quality. Panna building had one columns of doubtful
quality of concrete.
A sample of 5 columns and 6 beams were taken up for combined UPV and RH test. The probable
estimated strength of concrete varied from 10
N/mm
2
for columns C14 of C3 block to 24 N/mm
2
for
col. C-26 of block C-3. This is indicative of large variation on quality.
3.3.2 BEAMS
Six beams were tested, 3 each in B6 (Panna) building and B5 (Ratna) building. The beam in B6
showed good quality consistently. In Block B5 Ratna building, two beams showed fair quality of
concrete with high value of coefficient of variation (CV) and one beam with good quality. On the
whole USPV values in beams were on lower end of good quality range.
From the USPV tests of beams and columns, it was concluded that-
i. Quality of concrete varied significantly.
ii. Weak patches are observed either near the junction of beam or at bottom near the floor or at
both.
iii. The quality variation is reflected in probable estimated strength. The probable variation is from
10 N/mm
2
to 24 N/mm
2
. Generally the values found were between 14-16 N/mm
2
in sample
Location Core
dia
Area Load
(KN)
Comp.
strength
( N/mm
2
)
Heera bldg
Panna bldg
Ratna bldg
68mm
68mm
68mm
3629.89
-do-
-do-
95
60
90
26.17
16.52
24.79
58 Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
columns. The values of estimated possible strengths of concrete in beam varied from 13 N/mm
2
to 23 N/mm
2
in sample beams. In B5 block, these were from 19 N/mm
2
, 22 N/mm
2
and 23
N/mm
2
. Those in sample beams in B6 were 13, 14, 22 N/mm
2
.
The buildings were constructed with cement concrete (1cement:1.5fine aggregate:3coarse aggregate)
with minimum cube strength of 20 N/mm
2
, but the NDT showed that compressive strength was
found less than minimum strength required at many locations. Some members showed compressive
strength even less than 10 N/mm
2
indicating poor quality of concrete in all the three buildings.
3.4 CARBONATION TEST
Test for carbonation of concrete was carried out at site as per standard practice
1
and found that depth
of carbonation was found 78mm for columns and 35 mm for beam soffits. It means that carbonation
had already penetrated deeply beyond the clear cover of 40 mm of columns and 25 mm of beams
resulting in to severe corrosion of the rebars and hence delamination and spalls in the structure.
3.5 TEST FOR CHLORIDES
Spalls of concrete were collected from the site for chloride content and got tested from the
laboratory. As per lab test, the water soluble chloride content was found to be 1.84, 1.85 and1.06
gms / kg of concrete weight in Heera, Panna and Ratna buildings resp. As per IS 456-2000, the
permissible values of total acid soluble chloride in concrete at the time of placing are 0.6 Kg/ cubic
meter i.e 0.25 gm / Kg of concrete which means that chloride content in concrete is beyond the
permissible limits. The higher the chloride content during the construction stage or if subsequently
exposed to warm and moist conditions, the greater is the risk of corrosion of reinforcement. Due to
carbonation of concrete, excess chloride in concrete and poor workmanship in providing effective
concrete covers especially at beam column junction has led to spalling and delamination of concrete
covers exposing the reinforcement steel badly affecting the structural integrity of the multi-storeyed
buildings.
4. DAMAGE BY BHUJ EARTH QUAKE OF JAN’ 2001
On 26
th
Jan, 2001, an earth quake of magnitude 7.9 on Richter scale struck Gujarat and other parts of
India. The epicentre of the quake was Dhori Village, 20KM off Bhuj. Many buildings were
destroyed and some buildings developed cracks and other structural defects due to inadequate design
and poor quality of material and workmanship in construction. These buildings safely resisted the
earthquake loads but masonry walls were badly cracked while acting as shear walls for resisting
lateral loads due to earthquake. There was lot of diagonal shear cracks observed in GF quarters (Fig
5). Due to earth quake vibration, there were separation cracks between masonry walls and beams at
top and also between walls and columns (Fig 6). Plaster of walls simply got dismantled of its area
due to shaking. The same thing happened with plaster on columns and beams. Some cracks in beam-
column junctions were also observed.
Fig. 5- Diagonal shear cracks at GF Fig. 6- Separation cracks at GF quarter
59
Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
5. REPAIR STRATEGY - The following strategy was adopted for rehabilitation of buildings [2]
i. Removal of damaged plaster / concrete.
ii. Removal of corrosion on steel reinforcement by mechanical and chemical action and
further application of corrosion inhibitor.
iii. Application of bond coat of polymer - cement mix to join old concrete with new mortar.
iv. Repair of RCC columns, beams, slabs by polymer modified mortar.
v. Jacketing of some columns with concrete.
vi. Epoxy grouting in RCC columns, beams to repair cracks.
vii. Crack sealing in masonry walls with polymer modified mortar.
viii. Polymer modified non-shrinkage grouting in cracks of masonry walls.
ix. Concrete grading on terraces
x. Replacement of damaged cast iron drainage pipes and water supply GI lines.
xi. Sealing of drainage pipe joints with PMM.
xii. Re-plaster and Acrylic paint to exterior walls.
6. REPAIR METHODOLOGY- The repair of structural members were carried out as follows-
6.1 REMOVAL OF DAMAGED CONCRETE
At the location, where concrete cover had already spalled eg. Columns corners, soffit of beams, slabs
and fins, loose concrete was removed 25cm more than the length of spall. For other areas which were
not spalled, hammer sounding method was used to locate delaminated concrete and marked with
paint. Surface repair boundary with 5mm groove using concrete saw cutter with minimum edge
length was prepared. The beams, slabs were supported with props before removal of damaged
concrete. After it was ensured that the surface to which cement based polymer modified mortar was
to be bonded was sound, it was cleaned off all loose and foreign materials by means of stiff wire
brushing. All dust and loose particles resulting from such pre-treatments was removed by washing
with water under pressure[1].
6.2 REINFORCEMENT CLEANING AND ANTI CORROSIVE COATING
Fig.7 - Column rebars with anti -corrosive coating
All concrete sticking to the rebars was removed by light hammering and manual chipping. Wire
brush was used to remove unwanted oxide from steel surface completely. One coat of rust remover
was applied all round the steel rebars. The coverage rate of rust clear coating on the steel bars came
out to be about 3.86 sq. m per litre only much lesser than the claim in the technical brochures. Care
was taken that the backside of the bars also gets coated with the rust remover. The rust remover was
allowed to act for 24 hrs and then steel bars were rubbed with wire brush to remove the rust followed
60 Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
with washing with water jet to completely remove the rust. If the rust was not removed effectively
than another coat of rust remover was applied, waited for 10 minutes and then again rubbed with
wire brush[1].
Anti corrosive zinc primer was coated on freshly cleaned and dry reinforcing steel on complete
periphery as per manufacturer’s specifications and allowed the primer to dry for 4 hrs (Fig 7). The
second coat of zinc primer after 4hrs of the application of first coat was also applied. Care was taken
to cover all the steel without leaving even the smallest part of steel uncovered. The coverage rate of
zinc based anti –corrosion coating on the steel bars came out to be about 2.4 sq. m per litre of the
chemical
which was much lesser than the claims in the technical brochures. The bars having more
than 20% of the reinforcement steel bar cross sectional area corroded were replaced with the
additional reinforcement by welding with existing bars or by drilling holes in to concrete and
inserting the steel bars with epoxy mortar. There was severe corrosion of shear stirrups in beams
resulting in decrease in diameter by more than 25%, so these were also replaced with new U- shape
stirrups.
6.3 APPLICATION OF BONDING COAT TO SUBSTRATE
All concrete surfaces prior to application of bond coat was thoroughly inspected and made free
from any deleterious materials such as oil, dust, dirt etc. The surface was kept wet for 24hrs
ensuring that they are well saturated but free of surfaces water after natural drying. A bonding
slurry of cement and Acrylic polymer in the ration 1:1 (I cement: 1 acrylic polymer) by volume
with required quantity of water was prepared to a lump free creamy consistency. The coverage
rate was found to be 0.8-1.1 sq.m of the concrete substrate. The bonding slurry was worked
well into surface of the parent body using a stiff brush ensuring that no pin holes are visible. If
a second coat was felt necessary, the same was applied at right angle to first coat to ensure
complete coverage after the first coat was touch dry. The bonding slurry was applied to
prepared concrete substrate after tying in new reinforcement wherever specified. Care was
taken that cement based polymer modified mortar was applied as soon as possible after
application of bonding coat, but always during the open time of adhesive [1].
6.4 APPLICATION OF POLYMER MODIFIED MORTAR
There are no codes/standards available for preparation of polymer modified mortar for rehabilitation
of concrete structures, so extensive testing was carried out for different polymer samples from
different manufacturers yielding different strengths [2]. The buildings were originally constructed
with concrete mix (1 cement: 1.5 sand: 3 coarse aggregates) with minimum strength requirement of
20 N/mm
2
min., so it was decided that the polymer modified repair mortar must have compressive
strength of 25 N/mm
2
. Based on the polymer test reports, concrete mix used in the construction of
these buildings, extent of damage and technical guidance from CBRI, Roorkee, the following
specifications for polymer modified mortar preparation were designed.
Solid Content- 46% mini., Compressive strength -25 N/mm
2
min.,Tensile strength-3.5 N/mm
2
mini.
,Flexural strength- 8.5 N/mm
2
mini. ,Direct shear bond strength- 2 N/mm
2
mini.
Polymer modified mortar mix was prepared in the proportion Cement (OPC) 50 kg : sand (graded
Zone II )150 kg :Acrylic polymer @ 20-25% of cement content by weight and water cement ratio
was kept below 0.4 (by weight). With this mix, the laboratory test reports of one batch of acrylic
polymer yielded following strengths-
Solid Content- 51.2 %, Compressive strength- 42.13 N/ sqmm, Tensile strength- 4.01 N/sqmm,
Flexural strength -14.25 N/sqmm, Direct shear bond strength- 2.77 N/sqmm.
These strengths satisfied our specifications and hence rehabilitation of structural members was
61
Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
carried out with this mortar mix. The test cubes of size 7.06 cm x7.06 cm of the PMM prepared at
site for concrete repair were also got tested from the laboratory as quality assurance measure which
showed compressive strengths between 26 to 32.40 N/mm
2
meeting the specifications.
Fig.8 -A view of the building repaired with PMM
6.5 COLUMN JACKETING
Some of the columns were badly cracked throughout their height in the parking area and some had
deep spalls at corners due to rebar corrosion. Some columns were badly damaged at floor level.
These columns were jacketed with new rebars and jacketing concrete by 75mm thickness all-round
to increase its strength and stiffness and to protect its reinforcement from further corrosion (Fig 9).
The ready to use jacketing concrete in which coarse aggregate of 6-10 mm down size was to be
added as per recommendation of the manufacturer was used. The Jacketing concrete was of
following properties with water powder ratio of 0.21 at 30
0
C and with 100% aggregates:
Compressive strength- 30N/sqmm mini at 30days, Flexural strength -3.0N/sqmm mini at 30days ,
Young’s Modulus- 22 KN/sqmm.
Fig.9 Jacketing of columns from the footing level.
6.6 CRACK REPAIR
6.6.1 MASONARY CRACKS
The plasticized expanding grout admixtures along with Styrene Butadiene Rubber (SBR) polymer
was used for sealing of masonry wall cracks. The SBR polymer with the same specifications as that
for acrylic polymer was added to grout admixture for enhancing its bonding with cracked masonry
inside. The laboratory test of one of the batch of SBR polymer used in the work had following
properties:
62 Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
Total solid content- 51.1%, Compressive Strength- 42.80N/sq mm, Tensile strength- 4.91 N/sq mm,
Flexural strength- 11.86 N/sq mm, Bond strength - 3.06 N/ sq mm.
6.6.2 RCC CRACKS
Cracks in RCC members especially beam-column joints were grouted with epoxy grout of the
following composition specially formulated to meet the required specifications (100 gms GY257+21
gm Aradur 21 + 4 gms Aradur 2958) from Araldite and the grout was of the following properties:
Viscosity at 25
0
C max: 2 N/ sq m, Minimum Gel time: 30 minutes,14 days bond strength at 25
0
C -
3.5 N/ sq mm, Compressive yield strength at 7 days: 60 N/ sq mm, Tensile strength at 7 days: 45 N/
sq mm, Elongation at break min: 1 %.
Fig.10- Epoxy injection in beam-column junctions
7. QUALITY CONTROL AND ASSURANCE
All the construction materials were prior tested from reputed laboratories like Ahmedabad Textiles
Industrial Research Association (ATIRA), Nirma University, Ahmedabad & IIT-Mumbai to check
conformity to standards. Construction chemicals from reputed companies like STP, Roffe, Fosroc,
Sunanda, Ventico performance polymers were used for this work. The non-destructive testing was
carried out by M/s. KCT Consultancy Services and M/s. KBM Engineering Research Laboratory,
Ahmedabad.
.
8. POST REHABILITATION CONDITION OF BUILDINGS
The buildings rehabilitation was completed in 2003. All visible cracks, spalls and de-laminations of
concrete in beams, columns, fins and slabs were rehabilitated as per standard procedures, best quality
workmanship and strict supervision at site. Extensive material testing of every polymer stock
received at site was tested before use at site. The work was completed in 18 months as per desired
quality standards. After structural rehabilitation, the building exterior was painted with acrylic paint
Fig.11-Cracked column at the parking level Fig.12-Damaged slab below the toilet due to rebar corrosion
63
Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
“Apex” from Asian paints. After 9 years of successful performance of these buildings, some cracks,
spalls have been noticed mostly in parking level columns (Fig11), beam / slab soffits under the toilet
area, roofs (Fig 12) and fins due to reinforcement corrosion requiring some structural rehabilitation
work to avoid further deterioration due to corrosion of rebars.
CONCLUSIONS
The detailed investigation of the buildings with rebound hammer test, ultrasound pulse velocity test
and core tests, carbonation test and chloride tests have indicated that there is lot of variation in the
compressive strengths of concrete in beams as well as columns. At certain locations, the strengths
were found around 10 N/mm
2
only indicated poor quality of concrete practices adopted in the
original construction. Lower value of compressive strengths also indicates higher permeability of the
concrete leading to ingress of harmful agents like carbon dioxide gas , chlorides etc from the
environment resulting in corrosion of steel bars and disintegration of concrete covers. From this case
study, following recommendations / conclusions are drawn for durable concrete constructions
requiring minimum structural rehabilitation at later stages of life.
[1] There is no substitute for good quality concrete construction practices for durability of
reinforced concrete structures. The quality control of materials and workmanship viz. water-
cement ratio, concrete cover, compaction and curing etc. which are prerequisites for good
quality construction are very important parameters and must be strictly observed at site. Poor
quality concrete construction done cannot be rectified at a later date except repeated costly
repairs to keep the structure functional.
[2] To achieve the quality at site, the role of manpower is very significant. The engineers and
workers responsible for construction should be well experienced, quality conscious and must
be fully aware of the repercussions of poor quality work. Also sufficient technical staff
should be deputed for achievement of quality construction with full support and
encouragement from top management.
[3] The early deterioration of concrete structure is also due to poor maintenance practices. The
water supply and drainage system should be kept intact so that there is no leakage/ seepage
on the walls and no stagnated water on roofs due to overflow of water tanks or rains which
acts as an enemy to the structural integrity of the buildings.
[4] The repair/ rehabilitation of damaged structure should be carried out urgently to avoid further
deterioration with time so that the life of the structure and the occupants is not jeopardized.
[5] The design for structural rehabilitation should be carried out after laboratory testing of the
repair materials because the claimed strengths in the brochures from the manufacturers may
not always be achievable
5
.
[6] Structural rehabilitation is more challenging then new concrete construction. It requires
special considerations for evaluation of damage, selection of suitable material, technical
specifications, and techniques for repair and quality control of material and workmanship.
Therefore sufficient time and cost allocations should be made for durable rehabilitation work.
64 Varinder.K.Singh / Procedia Engineering 51 ( 2013 ) 55 – 64
ACKNOWLEDGEMENT
The author is thankful to ONGC Academy, Dehradun for granting permission to publish this
technical paper based on the rehabilitation project completed in 2003 in Ahmedabad Asset which
was awarded ACCE-ESSEN award in 2006 by Association of Consulting Civil Engineers
,Bangalore, for “Appropriate Use of Construction Chemicals and Epoxy for Rehabilitation /
Retrofitting of Civil Engineering Structures. “ The technical guidance and support from Central
Building Research Institute (CBRI), Roorkee is deeply acknowledged.
References
[1] Peter Pullar-Strecker, 1987. Corrosion Damaged Concrete Assessment and Repair,
Butterworths, London,UK
[2] Singh.V.K , 2005, Selection of polymers for repair and rehabilitation of RC structures, Point
of view, Indian Concrete Journal, p 35-38
