Ahmed Fathy Abdel-Azeem

2012 AIN SHAMS UNIVERSITY

[CONSTRUCTION ENGINEERING II REVISION]

Made By: Ahmed Fathy Abdel-Azeem

Supervised By: Dr.Amgad Talaat

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[CONSTRUCTION ENGINEERING II REVISION] January 14, 2012

Dr. Amgad Talaat Page 1

1) Draw a flow diagram showing the typical activities involved in the inspection and repair

of concrete structures?

Solution

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2) What are the two groups of concrete deficiencies? Explain briefly.

Solution

Structural Failure

Usually result from a design deficiency or an overloading condition. Overloads may

be either manmade or natural. An example of a man made overload is a load that

exceeds the allowable floor loading in a building. An example of a natural overload is

an earthquake.

Lack of Durability and Serviceability

It may be caused by material, production, or environmental factors. These three

factors were discussed in the three previous modules and will not be covered again.

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3) What are the reasons of conducting inspections?

Solution

To determine the present condition of the structure.

To determine the type, extent, rate and causes of deterioration.

To estimate the time remaining before repair or replacement.

To estimate the effects of deterioration on serviceability if repair or replacement is

deferred.

To determine if the proposed changes to the structure will affect the structure‟-s safety

and service life.



To estimate the most cost-effective means to prevent further deterioration to the structure.

To study the performance of a material under a specific exposure condition.

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4) Draw the general flow-chart of inspection?

Solution

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5) What are the conditions indicate the need for detailed inspection?

Solution

When the information gathered during a preliminary inspection indicates a need for

closer examination.

When either the inspectors or plant operators note potentially serious deterioration.

When there is a plan to increase significantly the loads on a structure.

When the condition of the structure has changed significantly since the last inspection.



6) What should field measurements include?

Solution

Delamination, voids, crack mapping.

Corrosion activity/potential mapping.

Carbonation.

Concrete cover, spacing of rebars.

Concrete strength and variability.

Concrete quality.

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7) Explain briefly what is meant by crack survey?

Solution

It‟s a function of crack length, direction, width, and depth.

Types: active or passive.

o Active Crack: a crack caused by;

Atmospheric variations- Temperature changes- Moisture drops- Settlement-

Loading conditions

o Passive Crack (Dormant) (Inactive): a crack caused by;

Construction errors _ Shrinkage _ Dead loads _ Internal temperature variations _

Shock waves

A good crack survey includes the following steps:

o Locate all cracks.

o Measure or estimate the widths and lengths of all cracks and then record the

results. (using comparator or crack microscope) (Tell-tale).

o Record the size and location of the cracks on a structural plan.

o Classify each crack as active (A) or passive (P).

o Determine the causes of all cracks, if possible.

o Locate internal cracks by sounding, impact echo testing, or ultrasonic pulse

velocity methods.

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8) How can you evaluate the crack enlargement?

Solution

Make a “tell-tale” of two thin glass or metal strips and position them side-by-side over the

crack. Bond the two plates on opposite sides of the crack, and make aligned marks across

each plate. Any changes in the distance between these two marks indicate relative movement

of the parts separated by the crack



9) Explain what is meant by concrete non-destructive tests? Choose one of them and

illustrate it in details.

Solution

Non-destructive tests:-

They are necessary tests done after the concrete has hardened to determine whether the

structure is suitable for its designed use (used also for quality control). Ideally such

testing should be done without damaging the concrete.

Examples: Pachometer (Cover) Survey _ Chloride Content Determination _ Moisture

Content Determination_ Ultrasonic Testing (Pulse Velocity Test) _ Rebound Hammer

Test _ Impact-Echo Test _ Concrete Core Extraction.

Ultrasonic Testing (Pulse Velocity Test):-

Applications

o Testing uniformity and relative quality

of concrete.

o Indicated the presence of crack and

voids.

Concept: Measuring the velocity of an ultrasonic

pulse through concrete.

Types of measurement: Direct _ Semi-direct _

Indirect

Factors: Density _ Voids _ Cracks _ Coarse

aggregates _ Rebars.

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10) Explain what is meant by concrete components’ tests? Choose one of them and

illustrate it in details.

Solution

Ensuring that all concrete materials are satisfied with specifications and well stored.

(i.e. Raw materials must be with the contracted conditions).

Components are mixing water, cement, aggregates, and admixtures.

Types: Initial _ Periodic _ Additional Tests.

For Example: Testing of Cement

o The fineness of cement

o The initial and final setting time of cement

o Soundness of cement

o Compressive strength of cement

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11) What are the reasons of applying a load test on concrete element/elements? Explain the

procedure of applying the load test?

Solution

Reasons:

o Changing the type of structure usage.

o If listed in project specification.

o Having doubts in efficiency of structural elements.

o Presence of irregular settlement during construction.

Procedure:

o Subjecting the different elements with additional loads

o Record deflection readings before and after loading

o Compare noticed deflections with the max accepted limit

o If unsatisfied; repeat test after 72 hours, otherwise element will be unaccepted.

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12) What are the different methods of strengthening an RC element?

Solution

Crack‟s Treatment: painting with epoxy material.

Horizontal Narrow Crack‟s Treatment

o Open the crack wider

o Fill it with epoxy material from one side only

o Clean the crack ( after concrete hardening)

Deep Crack‟s Treatment ( Injection)

o Open the crack wider

o Fill it with epoxy material from two sides

o Make holes at 25-50 cm spacing, and fill with epoxy material

o Inject the first side through pipes, go on the other side

Wide Crack‟s Treatment

o Clean the crack after opening at V shape

o Fill with Cement, Polymer, and epoxy materials

Building Crack‟s Treatment

o Clean the crack after opening at V shape

o Paint then fill the interior surface with certain materials

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13) Explain the procedure of strengthening a reinforced concrete column in ground

floor using a reinforced concrete jacket?

Solution



Remove the paining layer and clean the surface

Insert bars to fix the new stirrups in both directions at 25-50 cm spacing (By making

holes with the corresponding rebar diameter + 2 mm, and clean them and fill).

Vertical bars are inserted with the same number of that of column and diameter

Vertical bars are inserted before stirrups fixing

Column surface is fully painted with epoxy material ( after cleaning and filling holes)

Pour the concrete of the RC jacket



14) Using neat sketches, explain the main difference between good and bad storage of the

following materials: cement – fine and coarse aggregate – shuttering wood –

reinforcement steel.

Solution

Cement

Aggregates

Reinforcement Steel

GOOD BAD

GOOD/fine GOOD/coarse

e BAD

GOOD

BAD



Shuttering wood

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15) How can we prevent the failure of excavation sides in site?

Solution

Applying safe side slopes with different depths.

Sides strengthening with longitudinal and transverse wood bars.

Using pre-cast barriers

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16) What are the steps of replacement for bad types of soil? And what are the soil

replacement types?

Solution

Steps

o Distinguish the new soil layers

o Compact each layer by compactor (هراس)

o Put a sand layer for leveling

Types

o Fine and Coarse aggregates soil.

o Fine aggregates soil.

o Coarse aggregates soil.

o Plain (weak) concrete soil.

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17) What are the different methods of mixing concrete? And when can we use each of

them?

Solution

Manual (hand-made) Mixing: For small traditional works.

GOOD BAD



Mechanical Mixing

o In-situ Mixer: small mixer availability in site (Traditional Projects)

o Central Ready Mix Stations: in-site or near it (Large Projects)

o Concrete Mix Trucks: site is far away from water resources

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18) What are the precautions of casting concrete?

Solution

Selecting appropriate pump location to ensure reaching all places.

Max casting height for columns is 2.50 m.

Thicker slabs should be casted at layers.

Determining the positions of casting stoppage.

Main beams should be casted first.

For casting on old concrete; its surface must be roughed.

Super Plasticizers could be used to increase workability.

Environmental conditions considerations.

Max time of concrete existence in truck is 2 hours.

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19) What are the different types of concrete joints?

Solution

Casting (Pouring) Joints: for large volume of poured concrete.

Expansion Joints: for buildings of length more than 30-40 m.

Settlement Joints: to avoid differential settlement.

Control Joint: to allow slab to expand in horizontal direction.

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20) What are the different types of concrete curing?

Solution

Submerging in water: like lakes (horizontal surfaces and floors)

Water spraying; keep surface moist and preventing drying

Covering with moist overlaps

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21) State the time after which we can remove the shuttering of the following reinforced

concrete elements: columns, beams, slabs and cantilever elements.

Solution

Columns & Sides: T= 24 hours

Beams & Slabs: T= 2 L + 2 days

Cantilevers: T= 4 L + 2 days

If forms carries additional loads: T = 28 days

If temperatures decreases than 15 c ; postpone removing of forms

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22) What are the types of quality control inspection programs?

Solution

Adjustment of Design‟s Quality (Quality Control):

All required calculations should be done to determine the best proportions in designing

the concrete mix in both cases of fresh and hardened.

Adjustment of Raw materials „Quality (Total Quality Management):

put a plan to good raw materials according to specifications, taking into consideration

that it must be at the required quality level during all the project stages.

Adjustment of Product‟s Quality (Quality Assurance):

It‟s to control quality during the construction stages to ensure satisfaction with

specifications.

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23) State briefly the inspection plan (field inspection) guidelines?

Solution

Structural Design Revision

Technical Inspection for Materials

Periodic Technical Inspection

Out site Technical Inspection

Additional Tests for Technical inspection

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Ahmed Fathy Abdel-Azeem

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