Design & Construction Errors- How it Affects Repair and Rehabilitation of Structures

DESIGN &
CONSTRUCTION
ERRORS
HOW IT AFFECTS REPAIR & REHABILITATIONOF
STRUCTURES
SRISHTIWAKHLOO B.TECH CE (HONS.) https://in.linkedin.com/in/srishti-wakhloo
BUILDING MAINTENANCE & REPAIRS

CONTENTS
■ Introduction
■ Design and Detailing Errors
– Causes
■ Types of Design Errors
■ Construction Errors
– Causes
■ Types of Construction Errors
■ Effect of Design & Construction Errors on Repair & Rehabilitation
■ Conclusion
■ References
2SRISHTIWAKHLOO B.TECH CE (HONS.) https://in.linkedin.com/in/srishti-wakhloo

INTRODUCTION
■ In buildings, repair & rehabilitation become necessary, as some parts of the building
naturally tend to deteriorate & become more defective.This may also happen due to
lack of maintenance.
■ Repair:To restore (something damaged, faulty, or worn) to a good condition, for
example repair of leakage in buildings, etc.
■ Rehabilitation:To restore something to it’s good or original condition
■ Design and construction errors increase the cost and schedule overruns

CRACKSINCONCRETE
BEFORE
HARDENING
DRYING
PLASTIC
SHRINKAGE
SETTLEMENT
SHRINKAGE
BLEEDING
DELAYED CURING
CONSTRUCTIONAL
FORMWORK
MOVEMENT
EXCESS VIBRATION
SUBGRADE
SETTLEMENT
FINISHING
EARLY FROST
DAMAGE

CRACKSINCONCRETE AFTER HARDENING
UNSOUND MATERIALS
CEMENT
AGGREGATES
EXCESS SILT, MUD &
DUST
LONG TERM DRYING
SHRINKAGE
THERMAL
HEAT OF HYDRATION
EXTERNAL
TEMPERATURE
JOINTS IN CONCRETE
ELEVATED
TEMPERATURE
FREEZING & THAWING
MOISTURE
MOVEMENTS
TRANSITION ZONE
BIOLOGICAL
STRUCTURAL DESIGN
DEFICIENCIES
CHEMICAL
SULPHATE ATTACK
ALKALI-AGGREGATE
REACTION
ACID ATTACK
SEA WATER
CARBONATION
CHLORIDE ATTACK
CORROSION OF
REINFORCEMENT

DESIGN & DETAILING
ERRORS
A deviation from the plans and specifications
Responsibility of owner, designer and contractor

CAUSES
■ Accuracy of drawings
■ Number of design omissions and ambiguities
■ Inadequacy within plans and specifications
■ Quality of facility

TYPES OF DESIGN
ERRORS

TYPES OF DESIGN ERRORS
1. Inadequate Structural Design
2. Poor Design Details
A. AbruptChanges in Section
B. Insufficient Reinforcement at Corners and Openings
C. Inadequate Provision for Deflection
D. Inadequate Provision for Drainage
E. InsufficientTravel in Expansion Joints
F. Incompatibility of Materials
G. Neglect of Creep Effect
H. Rigid Joints Between Precast Units
I. Unanticipated Shear Stresses in Piers, Columns, or Abutments
J. Inadequate Joint Spacing in Slabs

1. INADEQUATE STRUCTURAL
DESIGN
■ CAUSES
– Due to inadequate structural design the
concrete is exposed to greater stress than
it can handle or strain in concrete
increases more than its strain capacity and
fails
■ SYMPTOMS
– Spalling of concrete due to high
compressive strength
– Cracking of concrete due to torsion and
shear stress
■ PREVENTION
– Thorough review of all design calculations
– Careful review of rehabilitation methods,
if any

2. POOR DESIGN DETAILS
■ CAUSES
– Localised concentration of high stresses in structural members
■ SYMPTOMS
– Cracking of concrete that allows water or chemicals to pass through concrete
– Seepage through structural members
– Structural failure
■ PREVENTION
– Thorough and careful review of all design calculations

2A. ABRUPT CHANGES
IN SECTION
■ SYMPTOMS
– Cracking because of stress
concentrations
■ PREVENTION
– Use of relatively thin sections
rigidly tied into massive
sections or patches and
replacement concrete that are
not uniform in plan dimensions
2B. INSUFFICIENT
REINFORCEMENT AT
CORNERS AND
OPENINGS
■ CAUSES
– Increased stress concentration
at corners
■ SYMPTOMS
– Cracking of concrete
■ PREVENTION
– Provide additional
reinforcement in areas where
stress concentrations are
expected to occur

2C. INADEQUATE
PROVISION FOR
DEFLECTION
■ CAUSES
– Loading of members or sections
beyond the capacities for which
they were designed
■ SYMPTOMS
– Cracking of walls or partitions
due to loadings
2B. INADEQUATE
PROVISION FOR
DRAINAGE
■ CAUSES
– Ponding of water caused by
poor attention to details of
draining
– Saturation resulting in severely
damaged concrete in an area
subjected to freezing and
thawing
■ SYMPTOMS
– Leakage may result in damage
to the interior structure
– Staining and encrustations on
the structure

2E. INSUFFICIENT
TRAVEL IN EXPANSION
JOINTS
■ CAUSES
– Inadequately designed expansion
joints
■ SYMPTOMS
– Spalling of concrete adjacent to
the joints
■ PREVENTION
– The full range of possible
temperature differentials that a
concrete may be expected to
experience should be taken into
account in the specification for
expansion joints
2F. INCOMPATIBILITY OF
MATERIALS
■ CAUSES
– The use of materials with
different properties (modulus of
elasticity or coefficient of
thermal expansion) adjacent to
one another
■ SYMPTOMS
– Cracking or spalling as the
structure is loaded or as it is
subjected to daily or annual
temperature variations

2G. NEGLECT OF CREEP
EFFECT
■ CAUSES
– Inadequate provision for
deflections
– Neglect of creep in pre-stressed
concrete members may lead to
excessive prestress loss
■ SYMPTOMS
– Cracking as loads are applied
2H. RIGID JOINTS
BETWEEN PRECAST
UNITS
■ SYMPTOMS
– Cracking or spalling
■ PREVENTION
– Designs utilizing precast
elements must provide for
movement between adjacent
precast elements or between
the precast elements and the
supporting frame

2I. UNANTICIPATED
SHEAR STRESSES IN
PIERS, COLUMNS, OR
ABUTMENTS
■ CAUSES
– Lack of maintenance
– Freezing of expansion bearing
assembles causing horizontal
loading to be transferred to the
concrete elements supporting
the bearings
■ SYMPTOMS
– Cracking of concrete
– Entry of water into the
concrete
2J. INADEQUATE JOINT
SPACING IN SLABS
■ SYMPTOMS
– Cracking of slabs-on-grade

17
INSUFFICIENT
REINFORCEMENT AT
CORNERS AND OPENINGS
INADEQUATE PROVISION FOR
DEFLECTION
INADEQUATE PROVISION FOR
DRAINAGE
BLUETSHUMI
ABRUPT CHANGE IN SECTION
INSUFFICIENTTRAVEL IN EXPANSION
JOINTS

CONSTRUCTION
ERRORS
Mistakes or inadequacies in a structure's own construction damage it partly
or completely

CAUSES
■ May occur due to failure to follow specified procedures and good practice or outright
carelessness
■ May not lead to failure or deterioration of concrete
■ May have adverse impact on the structure with time

TYPES OF
CONSTRUCTION ERRORS

TYPES OF CONSTRUCTION ERRORS
1. AddingWater to Concrete
2. ImproperAlignment of Formwork
3. ImproperConsolidation or
Compaction of Concrete
A. Bug Holes
B. Honeycombing
C. Over-consolidation
4. ImproperCuring
5. Improper Location of
ReinforcementSteel
21
6. Movement of Formwork
7. Premature Removal of Shores or
Reshores
8. Settling of Concrete
9. Settling of the Subgrade
10. Vibration of Freshly Placed
Concrete
11. Improper Finishing of FlatConcrete
Surface

1. ADDING WATERTO CONCRETE
22
CAUSES EFFECTS
Addition of water to the
concrete in a delivery
truck to increase slump
and decrease pouring or
placement effort
• Concrete with
lowered strength
and reduced
durability
• W/c ratio of the
concrete increases,
the strength and
durability will
decrease
Water is commonly
added during finishing
of structural member
Scaling, crazing, and
dusting of the concrete

2. IMPROPER ALIGNMENT OF
FORMWORK
■ EFFECTS
– Discontinuities on the surface of the concrete
 These discontinuities are unsightly in all circumstances
 Their occurrence may be more critical in areas that are subjected to high velocity flow
of water, where cavitation-erosion may be induced, or in lock chambers where the
“rubbing” surfaces must be straight

3. IMPROPER CONSOLIDATION OR
COMPACTION OF CONCRETE
■ EFFECTS
– Improper compaction of concrete may result in a variety of defects, the most
common being bug holes, honeycombing, and cold joints
24
BUG HOLES HONEYCOMBING OVER-
CONSOLIDATION

These can be reduced by
inserting the vibrator
more frequently, and as
close as possible to the
form face without
touching the form, and
slower withdrawal of the
vibrator.
Obviously, any or all of
these defects make it
much easier for any
damage-causing
mechanism to initiate
deterioration of the
concrete.
It is usually defined as a
situation in which the
consolidation effort
causes all of the coarse
aggregate to settle to the
bottom while the paste
rises to the surface. If this
situation occurs, it is
reasonable to conclude
that there is a problem of
a poorly proportioned
concrete rather than too
much consolidation.
25
These are formed when
small pockets of air or
water are trapped against
the forms.
A change in the mixture
to make it less “sticky” or
the use of small vibrators
worked near the form has
been used to help
eliminate bug holes.
3A
BUG HOLES
3B
HONEYCOMBING
3C
OVER-CONSOLIDATION

4. IMPROPER CURING
Curing is probably the most abused aspect of the concrete construction process. Unless
concrete is given adequate time to cure at a proper humidity and temperature, it will not
develop the characteristics that are expected and that are necessary to provide durability.
■ SYMPTOMS
– Various types of cracking and surface disintegration
– Failure to achieve anticipated concrete strengths, structural cracking may occur

5. IMPROPER LOCATION OF
REINFORCING STEEL
■ CAUSE
– This section refers to reinforcing steel that is improperly located or is not adequately
secured in the proper location
■ EFFECTS
– First, the steel may not function structurally as intended, resulting in structural
cracking or failure. E.g.is the placement of welded wire mesh in floor slabs. In many
cases, the mesh ends up on the bottom of the slab which will subsequently crack
because the steel is not in the proper location
– The second type of problem stemming from improperly located or tied reinforcing
steel is one of durability. The tendency seems to be for the steel to end up near the
surface of the concrete. As the concrete cover over the steel is reduced, it is much
easier for corrosion to begin

6. MOVEMENT OF FORMWORK
■ CAUSE
– Movement of formwork during the period while the concrete is going from a fluid
to a rigid material may induce cracking and separation within the concrete
■ EFFECTS
– A crack open to the surface will allow access of water to the interior of the
concrete.
– An internal void may give rise to freezing or corrosion problems if the void
becomes saturated

7. PREMATURE REMOVAL OF SHORES
OR RESHORES
■ CAUSE
– If shores or reshores are removed too soon, the concrete affected may become
overstressed and cracked
■ EFFECTS
– In extreme cases there may be major failures

8. SETTLING OFTHE CONCRETE
■ CAUSE
– During the period between placing and initial setting of the concrete, the heavier
components of the concrete will settle under the influence of gravity
– This situation may be aggravated by the use of highly fluid concretes
■ EFFECTS
– If any restraint tends to prevent this settling, cracking or separations may result.
– These cracks or separations may also develop problems of corrosion or freezing if
saturated

9. SETTLING OFTHE SUBGRADE
■ CAUSE
– Settling of the subgrade during the period after the concrete begins to become
rigid but before it gains enough strength to support its own weight
■ EFFECTS
– Cracking may also occur
– Sags and Humps (Localized Depressions) may occur

10.VIBRATION OF FRESHLY PLACED
CONCRETE
■ CAUSE
– Most construction sites are subjected to vibration from various sources, such as
blasting, pile driving, and from the operation of construction equipment. Freshly
placed concrete is vulnerable to weakening of its properties.
■ EFFECTS
– If subjected to forces, concrete matrix may disrupt during setting

11. IMPROPER FINISHING OF FLAT
CONCRETE SURFACE
A. Adding water to the surface: Evidence that water is being added to the surface is the
presence of a large paint brush, along with other finishing tools.The brush is dipped in
water and water is “slung” onto the surface being finished.
B. Timing of finishing: Final finishing operations must be done after the concrete has
taken its initial set and bleeding has stopped.The waiting period depends on the
amounts of water, cement, and admixtures in the mixture but primarily on the
temperature of the concrete surface. On a partially shaded slab, the part in the sun
will usually be ready to finish before the part in the shade.

11. IMPROPER FINISHING OF FLAT
CONCRETE SURFACE
C. Adding cement to the surface:This practice is often done to dry up bleed water to
allow finishing to proceed and will result in a thin cement-rich coating which will craze
or flake off easily.
D. Use of tamper: A tamper or “jitterbug” is unnecessarily used on many jobs.This tool
forces the coarse aggregate away from the surface and can make finishing easier.This
practice, however, creates a cement-rich mortar surface layer which can scale or
craze.A jitterbug should not be allowed with a well designed mixture. If a harsh
mixture must be finished, the judicious use of a jitterbug could be useful.
E. Jointing:The most frequent cause of cracking in flatwork is the incorrect spacing and
location of joints.

35
MOVEMENT OF FORMWORK SETTLING OF CONCRETE SETTLING OF SUBGRADE
IMPROPER FINISHING OF FLAT
CONCRETE SURFACE
IMPROPER CURING- PLASTIC SHRINKAGE

EFFECT OF DESIGN AND
CONSTRUCTION ERRORS
ON REPAIR &
REHABILITATION

37
S.NO. DESIGN ERRORS REPAIR & REHABILITATIONTECHNIQUES
1. Inadequate Structural Design
• Plate Bonding Method
• RC Jacketing of beams & columns with RCC
• Strengthening by Fibre Reinforced Polymer
(FRP)
2. Poor Design Details
• RC Jacketing
• Increase in longitudinal reinforcement
2A Abrupt Changes in Section
• Providing struts for span reduction of beam
• Concrete strengthening
2B
Insufficient Reinforcement at Corners and
Openings
• Installing Ferro-cement plates at corners
• Providing vertical reinforcement at corners,
junction of walls
2C Inadequate Provision for Deflection Rebuilding portions of the wall
2D Inadequate Provision for Drainage
• Fixing of drainage pipes
• Drainage of sloped roof with tiles
• Waterproofing
• Correction of floor leaks & traps

38
S.NO. DESIGN ERRORS REPAIR & REHABILITATIONTECHNIQUES
2E Insufficient travel in expansion joints Repair or replace expansion joints
2F Incompatibility of materials
• Grout injection
• Concrete ring beams & roof & floor
substitution
• Bond coats
2G Neglect of Creep Effect
• Bed Joints Reinforcement Technique
• Fibre Reinforced Polymer Composite (CFRP)
2H Rigid Joints Between Precast Units Shear Keys/ Mechanical Anchors
2I
Unanticipated Shear Stresses in Piers, Columns,
or Abutments
• Cutting new expansion joints, jacking
structure, isolation bearings, removal of
portions of structure
• Providing struts for span reduction of beam
• Reducing dead loads and live loads
2J Inadequate Joint Spacing in Slabs
• External stressing
• FRP Method
• Plate Bonding

39
S.NO. CONSTRUCTION ERRORS REPAIR & REHABILITATIONTECHNIQUES
1. Adding Water to Concrete
• Epoxy Coating (Epoxy Resin + Hardener)
• Polymer Resin based Coating
• Shotcrete/ Gunite
2. Improper Alignment of Formwork
• Shear Keys
• Preformed Foam Gaskets
• Cast In Place Foam
3
Improper Consolidation or Compaction of
Concrete
Fibre Reinforced Concrete
3A Bug Holes Epoxy Resin
3B Honeycombing
• Polymer Modified Cement Mortar (PMM)
• Polyester Putty
• Epoxy putty
• Emulsified Styrene Butadiene Rubber(SBR)
Polymer
3C Over-consolidation
• Polymer Modified Concrete (PMC)
• Epoxy Resin

40
4. Improper Curing
• Elastomeric sealer
• ‘Flexible’ epoxy filler
• Membrane or special mortar
• Strengthening by Fibre Reinforced Polymer
(FRP)
5. Improper Location of Reinforcement Steel
• Introducing new reinforcement bars for
structural connections
• Fibre Reinforced Polymer (FRP) for durability
6. Movement of Formwork
• Coarse aggregate and grout
• Dry-pack
• Waterproofing by Acrylic Polymer or SBR
Polymer
7. Premature Removal of Shores or Reshores
• Cutting new expansion joints, jacking
structure, isolation bearings, removal of
portions of structure
• Caulking for live cracks

41
8. Settling ofThe Concrete
• Fusion Bonded Epoxy Powder Coatings
(FBEC)
• Cathodic Protection
• Chloride Removal
• Realkalisation
• Epoxy
• FRP Strengthening
9. Settling ofThe Subgrade
• Patching with Base Repair
• Overlay Patches
• Grader Patching
10. Vibration of Freshly Placed Concrete
• Fibre Reinforced Concrete (FRC)
• Re-concreting
• Hardened Cement Paste (HCP)
11. Improper Finishing of Flat Concrete Surface
with Bond Coat
• Shotcrete with Finishing Plaster and Water
Curing
• Polyurethane Coat

CONCLUSION
■ A structure, if regularly maintained, will not need extensive repair and rehabilitation
and the cost of the same would also go down.
■ Design errors' onset is during the stage of planning. These can be prevented by careful
and thorough inspection of drawing at each stage.
■ Construction errors' commence during the stage of execution and can be controlled by
inspection, excepting when environmental factors govern the error.
■ Even after the identification of repair/rehabilitation method, it is significant to know
the specifications of the materials to be used, so that these can be altered depending
upon the need.

REFERENCES
■ http://theconstructor.org/concrete/design-detailing-errors-concrete-construction/8190/
■ http://theconstructor.org/concrete/construction-errors-during-concreting-at-site/8184/
■ http://nairaproject.com/projects/080.html
■ Concrete Problems & RepairTechniques- Professor Khaled A. Soudki, Peng
■ CPWD Handbook on Repair & Rehabilitation of RCC Buildings
■ Repair & Rehabilitation of Structures- Prof. M.Vijayalakshmi
■ WSDOT Maintenance Manual- Chapter 3- Page 3 to 28

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