common concrete defects- training presentation draft

8/10/2019 Common Concrete Defects- Training Presentation Draft

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COMMON CONCRETE

DEFECTS & REMEDIES

Quality Awareness Training-02


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Concrete defects, what are the issues?

Reasons for their development of Concrete defects

may be.

Poor Materials

Poor Construction Practice/Construction faults Bug holes/Pinholes

Honeycombing

Exposed Reinforcing steel / Concrete Cover

Cold joints

Irregular surface

Popouts /Bulges

Poor Supervision or a Combination

Surface Cracks (shrinkage/Plastic before hardening)

Dimensional Deviations

Chip off and Damages


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Poor Construction Practice/Construction

faults Bug holes/Pinholes

Picture Bad Picture Good


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Poor Construction Practice/ Construction

faults Cement Slurry Leakages



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Poor Construction Practice/ Construction

faults Honeycombing



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faults Rebar exposed & Concrete Cover

Picture Good Picture Bad


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faults Cold Joints



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faults Top Surface Finish and Defects



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Perfect Repair of Pinhole/Bug Holes

Cosmetics Repairing Materials & Tools



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Perfect Repair of Pinhole/Bug HolesCosmetics Repairing MaterialsSample Finish



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Possible Causes Poor Concrete compaction due to ineffective vibration or

Rebar congestion. Concrete slurry leakage along the perimeter side forms due

to:

*Loose or missing supports /fixing bolts

* Damaged Rubber gasket seal.

* Defective formwork/Mould

Inadequate concrete vibrator and negligence to vibrate

Less concrete cover and spacing between the reinforcement

Inadequate supervision and no hammering the side surface to

remove the voids/Bubbles .

Remedial Measures Honeycombing and pin holes must be rectified immediate

after stripping of sides with approved repairing Material.

Excessive Honeycombing & loose partials must be cleaned


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Vibration


Proper Vibration will avoid the Honey Comb, Pin hole Defects


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Formwork / Mould


Proper form Work / Mould will avoid the Concrete Slurry Defects


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Concrete Cover Spacing


Proper Covering Block will avoid the Rebar Exposed Defects and Design

Failure


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Damages occurring mainly due to Inadequate

Supervision & Negligence.

Supervision or a Combination

Dimensional Deviations, Chip off & Damages


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Dimensional & Formwork Deviations


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Possible Causes Mould of forms may not be sufficiently rigid to maintain

specified tolerance during concrete pouring Precast elements may not have gained sufficient concrete

strength when demoulded.

Train Operators and Riggers for Safe Lifting Operation

Top surface finish of precast elements may not be properly

leveled and troweled during production which result in

different levels & surface undulation.

Remedial Measures For minor deviation, corrective measures such as surface

grinding. Trimming/hacking and skim coat application can be

appropriately used to remedy the situation. Strictly follow the approved Method Statement .

Stripping and Lifting strictly follow the Cube results.


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Surface Cracks


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Surface Cracks


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Possible Causes Lifting and Stripping of Precast units before concrete mature

Cracks may have accrued during initial lifting due to friction

between the elements and casting Mould forms.

Inadequate supervision & Improper curing method; curing

time &temperature variations leads cracks on the surface

Uncontrolled concrete mix and Negligence while pumping

concrete, such as excess water and excess floating Inadequate handling Techniques

Insufficient lifting points; No appropriate tools & method

while lifting precast units.

Type of CracksA. Before Hardening: B. After Hardening:

Early frost damage Physical reactivity

Plastic Chemical reactivity

Construction Movement Thermal contraction/reactivity

Structural impact/Design loads


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Remedial Measures & Acceptance Tolerance

All the cracks should be examined by a qualified engineer to

determine the Types & Acceptance.

Depends on the location and seriousness of the cracks,

different repairs method can be used to correct the cracks.

Proper curing system and covering with Polythene sheets

must be improved for the fresh concrete to control Early

frost damage& Plastic cracks Surface cracks and Hairline cracks (not more than 0.3mm

width) can be repaired by cutting a V groove of specified

minimum depth along the crack lines, followed by patching.

Material used for the cracks repairGravity flow material, Injunction based Epoxy,

PVA based polymer grout, Cementations grout , etc.


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Test Paper

1. Which will avoid the Honey Comb, Pin hole Defects ?

a. Leveling b. Vibrator c. Shuttering oil2. Which will avoid the Concrete Slurry Defects ?

a. Proper Form Work b. Steel Work c. Cover Block

3. Which will avoid the Rebar Exposed Defects and Design Failure ?

a. Block Work b. Cover Block c. Form Work

4. What are the damages occurred due to Inadequate Supervision?

a. Dimensional deviation b. Pin hole c. Honey Comb

5. What type of crack Observed Before Hardening ?

a. Physical reactivity b. Chemical reactivity c. Construction

Movement


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Thank you

common concrete defects- training presentation draft

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