👉BASICS OF CRACKING PROBLEMS: @engineer03
.
▶The subject “ CRACKS “ or “ CRACKING “ in
concrete is indeed much debated. However, there is
inadequate clarity as to the reason for cracking and what may be done to limit its occurrence or
eliminate it altogether.
The phenomenon of the appearance of cracks in
concrete is often a subject that raises several
questions. Either at the initial stage or with time,
cracks may appear in a concrete structure. It should first of all be accepted that cracks of some type or other are inevitable in any concrete. They can be minimized to a large extent by proper practices.
*Cracks may be big or small, structural or non-
structural. All of them can be a nuisance by way of
either marring the appearance or function as a passage for atmospheric polluting gases and
moisture to either the body of concrete and causes
distress.
*Cracks in the concrete structure do not always
mean that the structure is not usable. As cracking
of concrete is inherent, what really matters is the
type of structure and the nature of cracking. Cracks
that are acceptable for building structures may not be acceptable for water relating structures.
Considering that cracking can never be completely
eliminated, it is necessary to be aware of the
causes, evaluation and the methods of repair
whoever required.
CRACKS Cracks are generally of tow types : Structural and nonstructural
*Cracks can occur in hardened or unhardened concrete.
*STRUCTURAL CRACKS
It is fundamental that hardened reinforced concrete cracks in the tensile zone when subjected to externally imposed structural loads. By means of appropriate design and detailing technique, these cracks can be limited to acceptable levels in terms
of structural integrity and aesthetics.
*NON_STRUCTURAL CRACKS
**Concrete is also liable to crack in both the plastic
and hardened states due to the nature of its
constituent materials. These intrinsic cracks are as inevitable as structural cracks. It is often possible
to predict when intrinsic cracks are likely and to
limit them to acceptable levels by means of good
design and/or proper construction techniques.
*DORMANT AND LIVE CRACKS:
Cracks caused by shrinkage, temperature gradient due to hydration and alkali silica reaction ( ASR ) are less dangerous the cracks caused by thermal expansion and loads. This is because shrinkage and hydration temperature gradient result in dormant cracks ( where the width does not vary with time) and other mechanisms result in live
cracks (where the width increases with time
Dormant cracks, especially narrow ones, are more
likely to undergo auto genius healing and
realkalisation. The crack may heal owing to
following conditions:
• carbon dioxide diffusing into the crack leading to
carbonation of the calcium hydroxide and
precipitation of calcium carbonate.
• Cement hydration due to presence of moisture.
• Hydration diffusing from the bulk concrete into the
heaked zone thereby increasing the pH in that area.
Live cracks are more likely than domant ones. They
result in collection of debris at the base owing to movement of the sides on the cracks. This can
impede temporarily the passage of depassivating
substances to the reinforcements. However,
autodeneous healing is unlikely with live cracks.
▶CAUSES OF CRACKING:
Cracking will occur whenever the applied strain exceeds the tensile strain capacity of the concrete.
*The tensile strain capacity of concrete varies with age and with
Age at which cracks may occur.
*Cracks can appear at any time. The age which
some typical can occur are given in the Table.
▶TABLE – AGE AT WHICH CRACKS MAY APPEAR:
*Sr. no. types of cracks Age
1. plastic shrinkage First few minutes or hours after
concreting .
2. plastic settlement First few minutes or hours
after concreting.
3. due to corrosion After one year or many years.
4. due to loads After loads are imposed and the
time duration of loading.
👇👇👇👇👇
.
▶The subject “ CRACKS “ or “ CRACKING “ in
concrete is indeed much debated. However, there is
inadequate clarity as to the reason for cracking and what may be done to limit its occurrence or
eliminate it altogether.
The phenomenon of the appearance of cracks in
concrete is often a subject that raises several
questions. Either at the initial stage or with time,
cracks may appear in a concrete structure. It should first of all be accepted that cracks of some type or other are inevitable in any concrete. They can be minimized to a large extent by proper practices.
*Cracks may be big or small, structural or non-
structural. All of them can be a nuisance by way of
either marring the appearance or function as a passage for atmospheric polluting gases and
moisture to either the body of concrete and causes
distress.
*Cracks in the concrete structure do not always
mean that the structure is not usable. As cracking
of concrete is inherent, what really matters is the
type of structure and the nature of cracking. Cracks
that are acceptable for building structures may not be acceptable for water relating structures.
Considering that cracking can never be completely
eliminated, it is necessary to be aware of the
causes, evaluation and the methods of repair
whoever required.
CRACKS Cracks are generally of tow types : Structural and nonstructural
*Cracks can occur in hardened or unhardened concrete.
*STRUCTURAL CRACKS
It is fundamental that hardened reinforced concrete cracks in the tensile zone when subjected to externally imposed structural loads. By means of appropriate design and detailing technique, these cracks can be limited to acceptable levels in terms
of structural integrity and aesthetics.
*NON_STRUCTURAL CRACKS
**Concrete is also liable to crack in both the plastic
and hardened states due to the nature of its
constituent materials. These intrinsic cracks are as inevitable as structural cracks. It is often possible
to predict when intrinsic cracks are likely and to
limit them to acceptable levels by means of good
design and/or proper construction techniques.
*DORMANT AND LIVE CRACKS:
Cracks caused by shrinkage, temperature gradient due to hydration and alkali silica reaction ( ASR ) are less dangerous the cracks caused by thermal expansion and loads. This is because shrinkage and hydration temperature gradient result in dormant cracks ( where the width does not vary with time) and other mechanisms result in live
cracks (where the width increases with time
Dormant cracks, especially narrow ones, are more
likely to undergo auto genius healing and
realkalisation. The crack may heal owing to
following conditions:
• carbon dioxide diffusing into the crack leading to
carbonation of the calcium hydroxide and
precipitation of calcium carbonate.
• Cement hydration due to presence of moisture.
• Hydration diffusing from the bulk concrete into the
heaked zone thereby increasing the pH in that area.
Live cracks are more likely than domant ones. They
result in collection of debris at the base owing to movement of the sides on the cracks. This can
impede temporarily the passage of depassivating
substances to the reinforcements. However,
autodeneous healing is unlikely with live cracks.
▶CAUSES OF CRACKING:
Cracking will occur whenever the applied strain exceeds the tensile strain capacity of the concrete.
*The tensile strain capacity of concrete varies with age and with
Age at which cracks may occur.
*Cracks can appear at any time. The age which
some typical can occur are given in the Table.
▶TABLE – AGE AT WHICH CRACKS MAY APPEAR:
*Sr. no. types of cracks Age
1. plastic shrinkage First few minutes or hours after
concreting .
2. plastic settlement First few minutes or hours
after concreting.
3. due to corrosion After one year or many years.
4. due to loads After loads are imposed and the
time duration of loading.
👇👇👇👇👇
5. due to weight Just after formwork support are
removed.6. due to chemical changes in hardened concrete After one or many years depending in
chemical attack from outside (sulphate ) Or
chemical reaction from within (ASR)
*CRITICAL CRACK WIDTH:
The most common reasons for controlling crack width are following:
APPERANCE : Unsightly cracking should be avoid
since it may cause concern to the occupants of the external structure. Ti may also contribute to
unsightly staining on exposed external surfaces,
where salts and rust are washed out from the crack.
*DURABILITY: Excessively wide cracks may lead to
corrosion of the reinforcement which in turn may lead to spalling of concrete due to the expansive nature of the corrosion process.
*WATER-TIGHTNESS: This is of importance in water
retaining structures.
In particular instances there may be other reasons for controlling cracking in addition to the three reasons cited above.
Crack width is, generally, to be taken to mean the
measurable width of a crack at the surface of
concrete. Crack width limitation is important from durability considerations. Most structural codes
prescribe maximum allowed crack widths.
Codes normally consider cracking caused by
external imposed conditions such as live loading and provide formula for calculating the crack width in the design phase. Mainly bending and tension or bending and axial load are considered. The direction of such cracks is perpendicular to the direction of the main reinforcement. Plastic
shrinkage cracks follow the line of reinforcement.
According to IS: 456-2000 the surface of the width
of the cracks should not in general exceeds o.3 mm
in members where cracking is not harmful and does not have any serious effect either on the
preservation of reinforcing steel or on the durability
of the structures.
In members, where cracking of the tensile zone is harmful either because they are moisture or in contact with soil or groundwater, an upper limlt of 0.2 mm is suggested.
*For aggressive conditions the surface width of
cracks should not generally exceed 0.1 mm. The crack width conditions the surface width of cracks should not be generally exceed 0.1 mm. The crack width is measured at the surface for the above purposes. However some other codes specify the
width at points near the reinforcement.
.
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removed.6. due to chemical changes in hardened concrete After one or many years depending in
chemical attack from outside (sulphate ) Or
chemical reaction from within (ASR)
*CRITICAL CRACK WIDTH:
The most common reasons for controlling crack width are following:
APPERANCE : Unsightly cracking should be avoid
since it may cause concern to the occupants of the external structure. Ti may also contribute to
unsightly staining on exposed external surfaces,
where salts and rust are washed out from the crack.
*DURABILITY: Excessively wide cracks may lead to
corrosion of the reinforcement which in turn may lead to spalling of concrete due to the expansive nature of the corrosion process.
*WATER-TIGHTNESS: This is of importance in water
retaining structures.
In particular instances there may be other reasons for controlling cracking in addition to the three reasons cited above.
Crack width is, generally, to be taken to mean the
measurable width of a crack at the surface of
concrete. Crack width limitation is important from durability considerations. Most structural codes
prescribe maximum allowed crack widths.
Codes normally consider cracking caused by
external imposed conditions such as live loading and provide formula for calculating the crack width in the design phase. Mainly bending and tension or bending and axial load are considered. The direction of such cracks is perpendicular to the direction of the main reinforcement. Plastic
shrinkage cracks follow the line of reinforcement.
According to IS: 456-2000 the surface of the width
of the cracks should not in general exceeds o.3 mm
in members where cracking is not harmful and does not have any serious effect either on the
preservation of reinforcing steel or on the durability
of the structures.
In members, where cracking of the tensile zone is harmful either because they are moisture or in contact with soil or groundwater, an upper limlt of 0.2 mm is suggested.
*For aggressive conditions the surface width of
cracks should not generally exceed 0.1 mm. The crack width conditions the surface width of cracks should not be generally exceed 0.1 mm. The crack width is measured at the surface for the above purposes. However some other codes specify the
width at points near the reinforcement.
.
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👉Today Tip @engineer03
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👉አሁን ደግሞ ስለ Lap length እንማማር @engineer03
.
▶Lap length in Reinforced
Concrete Lap length is one of the important term in the reinforcement. This is usually confused with
another important term called development length and anchorage length.
In this article, the lap lengths of bars is discussed. During the
placement of steel in Reinforced concrete
structure , if the required length of single bar
may fall short. To get the desired design length, lapping of two bars side by side is done.
An alternative to this is to provide mechanical couplers.
*steel bars overlapped
Lapping can be defined as the overlapping of two bars side by side to upto the design length. Usually, the stock length of steel bars is limited to 12m. *This is for easy
transportation of steel bars to the construction
site. For example, imagine there is a need to build a 100ft tall column. But it’s not practically available. Hence the bars are cut
every second story.
steel bars overlapped Then the tension forces are required to be transferred from one bar to the other bar at the location of discontinuity of the bar.
So the second bar is kept closely to the first bar and
overlapping is done.
This amount of overlapping between two bars is called “lap length”. *Lapping is usually done where minimum bending stress is encountered. In
general, lap length is 50d which means 50 times the bar diameter, if both bars are of same diameter.
*Lap length of bars with same diameter Lap length in tension: The lap length including anchorage value of hooks shall be For flexural tension – Ld or 30d whichever is greater is considered.
*For direct tension – 2Ld or 30d whichever is greater is considered.
*The straight length of lapping of bars shall not
be less than 15d or 20cm.
Lap Length in Compression: The lap length is equal to the development length calculated in compression but not less than 24d.
*For Different Diameter Bars: When the bars of different diameters are to be spliced, the lap length is calculated considering
the smaller diameter bar.
*Lap Splices:- Lap splices should not be catered for the bars
which are having diameter greater than 36 mm.
In such cases, welding should be considered.
*But if welding is also not feasible in some conditions, then lapping may be allowed for the bars larger than 36 mm diameter. But along with lapping, additional spirals of 6 mm should be provided around the lapped bars.
*Lap splice length in a footing Lap length for concrete of 1:2:3 Nominal mix: The Lapping length in tension (MS bar – mild
steel bar) including anchorage value is 58d. So
eliminating the anchorage value, the lap length
= 58d – 2*9d = 40d. (Where 9d = hook
*allowance up to 25 mm and k=2)
*Lap length for C-25 concrete:
*Columns – 45d
*Beams – 60d
*Slabs – 60d
This infers that if we need to lap 20 mm diameter column bars, a minimum lap of 45 * 20 = 900 mm is provided.
.
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.
▶Lap length in Reinforced
Concrete Lap length is one of the important term in the reinforcement. This is usually confused with
another important term called development length and anchorage length.
In this article, the lap lengths of bars is discussed. During the
placement of steel in Reinforced concrete
structure , if the required length of single bar
may fall short. To get the desired design length, lapping of two bars side by side is done.
An alternative to this is to provide mechanical couplers.
*steel bars overlapped
Lapping can be defined as the overlapping of two bars side by side to upto the design length. Usually, the stock length of steel bars is limited to 12m. *This is for easy
transportation of steel bars to the construction
site. For example, imagine there is a need to build a 100ft tall column. But it’s not practically available. Hence the bars are cut
every second story.
steel bars overlapped Then the tension forces are required to be transferred from one bar to the other bar at the location of discontinuity of the bar.
So the second bar is kept closely to the first bar and
overlapping is done.
This amount of overlapping between two bars is called “lap length”. *Lapping is usually done where minimum bending stress is encountered. In
general, lap length is 50d which means 50 times the bar diameter, if both bars are of same diameter.
*Lap length of bars with same diameter Lap length in tension: The lap length including anchorage value of hooks shall be For flexural tension – Ld or 30d whichever is greater is considered.
*For direct tension – 2Ld or 30d whichever is greater is considered.
*The straight length of lapping of bars shall not
be less than 15d or 20cm.
Lap Length in Compression: The lap length is equal to the development length calculated in compression but not less than 24d.
*For Different Diameter Bars: When the bars of different diameters are to be spliced, the lap length is calculated considering
the smaller diameter bar.
*Lap Splices:- Lap splices should not be catered for the bars
which are having diameter greater than 36 mm.
In such cases, welding should be considered.
*But if welding is also not feasible in some conditions, then lapping may be allowed for the bars larger than 36 mm diameter. But along with lapping, additional spirals of 6 mm should be provided around the lapped bars.
*Lap splice length in a footing Lap length for concrete of 1:2:3 Nominal mix: The Lapping length in tension (MS bar – mild
steel bar) including anchorage value is 58d. So
eliminating the anchorage value, the lap length
= 58d – 2*9d = 40d. (Where 9d = hook
*allowance up to 25 mm and k=2)
*Lap length for C-25 concrete:
*Columns – 45d
*Beams – 60d
*Slabs – 60d
This infers that if we need to lap 20 mm diameter column bars, a minimum lap of 45 * 20 = 900 mm is provided.
.
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👉DIFFERENCE BETWEEN
DEVELOPMENT LENGTH
AND LAP LENGTH @engineer03
.
➡In this article, I will discuss the differences
between development length and lap length. Let’s
get started.
➡DEVELOPMENT LENGTH: Development length is the length of bar required for transferring the stress into concrete. In simple words, the quantity of the rebar length that is actually required to be embedded into the concrete to achieve the desired bond strength between concrete andsteel by producing required
stress for the steel in that area.
*The formula for development is given below: Development length (Ld) = d x σs/τbd
Where
d = Diameter of the bar.
σs = Stress in the bar at the section considered
as design load.
τbd = Design bond stress.
.
➡LAP LENGTH: Lap length is the overlapping length of two bars side by side which gives required design length. In RCC structure if the length of a bar is not sufficiently available to make design length, lapping is done.
Suppose we need to construct a building of 20 m height. But there is no 20 m single bar available
in the market. The maximum length of rebar
available in the market is usually 12 m, so we need to join two bars of 12 m to get 20 m bar.
*The lap length varies from member to member. Lap length for tension members = 40d
Lap length for compression members = 50d. Where, d = Diameter of bars.
.
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👉DIFFERENCE BETWEEN
DEVELOPMENT LENGTH
AND LAP LENGTH @engineer03
.
➡In this article, I will discuss the differences
between development length and lap length. Let’s
get started.
➡DEVELOPMENT LENGTH: Development length is the length of bar required for transferring the stress into concrete. In simple words, the quantity of the rebar length that is actually required to be embedded into the concrete to achieve the desired bond strength between concrete andsteel by producing required
stress for the steel in that area.
*The formula for development is given below: Development length (Ld) = d x σs/τbd
Where
d = Diameter of the bar.
σs = Stress in the bar at the section considered
as design load.
τbd = Design bond stress.
.
➡LAP LENGTH: Lap length is the overlapping length of two bars side by side which gives required design length. In RCC structure if the length of a bar is not sufficiently available to make design length, lapping is done.
Suppose we need to construct a building of 20 m height. But there is no 20 m single bar available
in the market. The maximum length of rebar
available in the market is usually 12 m, so we need to join two bars of 12 m to get 20 m bar.
*The lap length varies from member to member. Lap length for tension members = 40d
Lap length for compression members = 50d. Where, d = Diameter of bars.
.
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👉Great Today Tip@engineer03
.
➡ለዛሬ የተለያዩ ሶፍትዌሮች እንካቹ ብሎናል
.
🅾በኢትዮጵያ ለመጀመሪያ ጊዜ
🅾አሁኑኑ Join በማረግ እና ለጓደኛዎ እና ለሚያቁት ሁሉ ሼር ያድርጉ።
.
➡ለዛሬ የተለያዩ ሶፍትዌሮች እንካቹ ብሎናል
.
🅾በኢትዮጵያ ለመጀመሪያ ጊዜ
🅾አሁኑኑ Join በማረግ እና ለጓደኛዎ እና ለሚያቁት ሁሉ ሼር ያድርጉ።
👉ዛሬ ደግሞ ስለ Load Combination በ አዲሱ የ EBCS ኮድ አብረን እንይ
.
Combo 1= DL + LL
Combo 2= 1.35DL + 1.5LL
Combo 3= DL + 0.3LL + EQx
Combo 4= DL + 0.3LL - EQx
Combo 5= DL + 0.3LL + EQy
Combo 6= DL + 0.3LL - EQy
Combo 7= max( Combo 2 up to 6)
.
.
ሁሌ ግን ይሄ ነው ማለት አይደለም፡፡ ለምሳሌ 0.3LL የሚለው
ህንፃውን የምንጠቀመው ለDomestic/residential purpose
ከሆነ ነው፡፡ Shop ከሆነ 0.6LL storage ከሆነ ደሞ 0.8LL
ይሆናል፡፡ ከዚህም በተጨማሪ ሁሉም ፎርሙላ ላይ የተለያዩ
ኮንዲሽኖች ስላሉ እነሱን ማየት ያስፈልጋል፡፡ መገኛቸውም EBCS
EN 1990: 2014 ከ Equation 6.9 እስከ 6.16 ነው፡፡
ፎርሙላዎቹ ውስጥ የሚገቡትን variable ለማግኘት ደሞ
check the Annex part እዩት።
.
combination ሰባት ነው ዘጠኝ ነው ስላልኩት ደሞ ብዙዎች
Earth Quakeም እያለ በሁለትና በሶስት Combination ሲሰሩ
ስላየው ነው፡፡ እንጂ ግዴታ 7 ወይ ምናምን መሆን የለበትም፡፡
ለምሳሌ Serviceability ብቻ ኮንሲደር ካደረግን አንድ ኮምቦ //
ማለትም DL+LL// ሊበቃ ይችላል፡፡ ፅሁፉ ግልፅ ስላልሆነና
ወዳልሆነ አቅጣጫ እንዳይወሰድ አንስቼዋለው፡፡
.
👉ለተጨማሜ የ ኮንስትራክሽን እውቀቶች...
🚩 እዚህ ይጫኑ
👇👇👇👇👇
@engineersWorks
@engineersWorks
.
Combo 1= DL + LL
Combo 2= 1.35DL + 1.5LL
Combo 3= DL + 0.3LL + EQx
Combo 4= DL + 0.3LL - EQx
Combo 5= DL + 0.3LL + EQy
Combo 6= DL + 0.3LL - EQy
Combo 7= max( Combo 2 up to 6)
.
.
ሁሌ ግን ይሄ ነው ማለት አይደለም፡፡ ለምሳሌ 0.3LL የሚለው
ህንፃውን የምንጠቀመው ለDomestic/residential purpose
ከሆነ ነው፡፡ Shop ከሆነ 0.6LL storage ከሆነ ደሞ 0.8LL
ይሆናል፡፡ ከዚህም በተጨማሪ ሁሉም ፎርሙላ ላይ የተለያዩ
ኮንዲሽኖች ስላሉ እነሱን ማየት ያስፈልጋል፡፡ መገኛቸውም EBCS
EN 1990: 2014 ከ Equation 6.9 እስከ 6.16 ነው፡፡
ፎርሙላዎቹ ውስጥ የሚገቡትን variable ለማግኘት ደሞ
check the Annex part እዩት።
.
combination ሰባት ነው ዘጠኝ ነው ስላልኩት ደሞ ብዙዎች
Earth Quakeም እያለ በሁለትና በሶስት Combination ሲሰሩ
ስላየው ነው፡፡ እንጂ ግዴታ 7 ወይ ምናምን መሆን የለበትም፡፡
ለምሳሌ Serviceability ብቻ ኮንሲደር ካደረግን አንድ ኮምቦ //
ማለትም DL+LL// ሊበቃ ይችላል፡፡ ፅሁፉ ግልፅ ስላልሆነና
ወዳልሆነ አቅጣጫ እንዳይወሰድ አንስቼዋለው፡፡
.
👉ለተጨማሜ የ ኮንስትራክሽን እውቀቶች...
🚩 እዚህ ይጫኑ
👇👇👇👇👇
@engineersWorks
@engineersWorks
👉CAUSES OF CRACKS IN CONCRETE YOU SHOULD
KNOW @engineer03
.
Cracking is one of the most common problems in concrete and it should be avoided seriously. *Different causes of
cracks in concrete
are described below:
1. SHRINKAGE:
Shrinkage is one of the major causes of cracking in hardened concrete. In drying shrinkage, the volume of concrete is gradually decreased and if the component is restrained against free movement, tensile stresses are developed which causes cracks.
2. TEMPERATURE CHANGES: The temperature variation in concrete results in the
differential volume change. When the tensile strain capacity of
concrete exceeds
due to the differential volume change, it will crack.
3. CHEMICAL REACTION:
Due to the alkaline nature of cement, it reacts with
the carbon dioxide
(CO2) present in the atmosphere resulting in an
appreciable increase
in the volume of the materials which finally leads to cracking.
4. POOR CONSTRUCTION PRACTICES:
Poor construction practices such as adding
excessive water to the
mix, lack of curing, poor compaction, using low-
grade materials, unreasonable placements of construction joints etc.
are also responsible for cracking in concrete.
5. ERRORS IN DESIGN & DETAILING:
Errors in design and detailing such as an
inadequate amount of
reinforcement, improper design of foundation,
precast members and
slabs, improper selection of materials, lack of
sufficient contraction
joints etc may result in excessive cracking.
6. CONSTRUCTION OVERLOADS & EARLY
FORMWORK REMOVAL:
The load induced in the structure during
construction can also lead to cracking especially at the younger stage when the formwork is
removed earlier.
7. ELASTIC DEFORMATION AND CREEP:
The different components of the building such as
wall, column, beam.
slab etc undergo elastic deformation when loaded.
The deformation of
concrete depends on the type of building materials
used in the construconstruction bricks, cement concrete
blocks etc. This
unusual deformation of concrete results in cracking.
8. CORROSION OF CONCRETE:
The corrosion of steel develops a huge amount of iron oxides and
hydroxide that have a much greater volume than the volume of metallic iron.
👇👇👇👇
@engineersWorks
KNOW @engineer03
.
Cracking is one of the most common problems in concrete and it should be avoided seriously. *Different causes of
cracks in concrete
are described below:
1. SHRINKAGE:
Shrinkage is one of the major causes of cracking in hardened concrete. In drying shrinkage, the volume of concrete is gradually decreased and if the component is restrained against free movement, tensile stresses are developed which causes cracks.
2. TEMPERATURE CHANGES: The temperature variation in concrete results in the
differential volume change. When the tensile strain capacity of
concrete exceeds
due to the differential volume change, it will crack.
3. CHEMICAL REACTION:
Due to the alkaline nature of cement, it reacts with
the carbon dioxide
(CO2) present in the atmosphere resulting in an
appreciable increase
in the volume of the materials which finally leads to cracking.
4. POOR CONSTRUCTION PRACTICES:
Poor construction practices such as adding
excessive water to the
mix, lack of curing, poor compaction, using low-
grade materials, unreasonable placements of construction joints etc.
are also responsible for cracking in concrete.
5. ERRORS IN DESIGN & DETAILING:
Errors in design and detailing such as an
inadequate amount of
reinforcement, improper design of foundation,
precast members and
slabs, improper selection of materials, lack of
sufficient contraction
joints etc may result in excessive cracking.
6. CONSTRUCTION OVERLOADS & EARLY
FORMWORK REMOVAL:
The load induced in the structure during
construction can also lead to cracking especially at the younger stage when the formwork is
removed earlier.
7. ELASTIC DEFORMATION AND CREEP:
The different components of the building such as
wall, column, beam.
slab etc undergo elastic deformation when loaded.
The deformation of
concrete depends on the type of building materials
used in the construconstruction bricks, cement concrete
blocks etc. This
unusual deformation of concrete results in cracking.
8. CORROSION OF CONCRETE:
The corrosion of steel develops a huge amount of iron oxides and
hydroxide that have a much greater volume than the volume of metallic iron.
👇👇👇👇
@engineersWorks
Questions with Answers Part 1 @engineersWorks
.
Q1. What is the Unit Weight of concrete?
A:- The unit weight of concrete depends on the type of aggregates and amount of voids. As per IS : 456-200 Unit weight of PCC is 24KN/m3 and RCC
is 25KN/m3
Q2. What is the unit weight of Steel?
A. The unit weight of Steel is 78.5KN/m3
Q3. What are the Nominal Concrete Mix proportions
for different grades:
A. Important: C-15 - 1:2:4 and C-5 - 1:4:8,C-20 and C-25 - 1:2:3,
(Cement:Sand:aggregate)
Q4. What is ductility?
A. Ductility is the Ability to deform under tensile
stress.
Q5. How to find the weight of steel bar used in
reinforcement?
A. Weight of Bar in kg/m = Dsquare/162.2 D- Dia
of bar in mm
Q6. What’s the difference between one-way slab
and two-way slab?
A. One way slab: Ratio of Longer Span / Shorter
span > 2 Two way slab: Ratio of Longer span/ shorter span <= 2
Q7. What is flat slab?
A. The slab which is supported on columns (Flab slab don’t have beams)
Q8. What do you mean by One storeyed, Two
storeyed building?
A. The building which has two floors is called two
storeyed building.
Q9. What’s the height of each floor?
A. 3m
Q10. What’s the length of rise and tread in Stair
case?
A. Rise – 150mm to 200mm, Tread – 250mm to 300mm
Q11. What’s the slope of Staircase?
A. As per IS 456, the slope or pitch of stair should
be between 25 degrees to 40 degrees.
Q12. What do you mean by the moment of inertia?
A. A quantity expressing a body’s tendency to resist
angular acceleration, which is the sum of the
products of the mass of each particle in the body
with the square of its distance from the axis of
rotation.
Q13. What is a crank length in the slab?
A. The crank length in Slab is 0.42 D. Where D is
Depth of Slab- Top cover – Bottom Cover.
Q14. What are the types of a slump?
A. True Slump: The concrete mass after the test when slumps evenly all around without disintegration is called the true slump.
*Shear Slump: When one-half of the concrete mass
slide down the other is called the shear slump. This type of slump is obtained in a lean concrete mix.
*Collapse Slump: When the sample is collapsed due to adding excessive water, it is known as collapse slump.
*Zero Slump: For very stiff or dry mixes it does not
show any changes of the slump after removing the
slump cone.
Q15. What is honeycomb in concrete? How is it
formed? How to eradicate honey comb in concrete?
A. Learn about Honeycomb concrete –
Q16. What is grouting?
A. Grout is a fluid form of concrete which is used
to fill the voids.
Q17. What is allowable moisture content in Fine
aggregate for the concrete mix?
A. We won’t use the aggregate if its moisture
content is more than 5%.
Q18. What do you mean by segregation?
A. Segregation is a separation of cement, sand from aggregate. This is caused due to Water
cement ratio and when concrete is poured about
more than 1.5m
Q19. What is Seepage?
A. Slow percolation of water through soil is called
Seepage.
Q20. What is the Compressive Strength of brick?
A. Second class brick-70kg/cm2
First class brick-105kg/cm2 Fire brick-125kg/cm2
Q21. How do you check the quality of cement on
the site?
A. 1. Date of Mfg: Cement strength decreases with
its age.
2. Color: Colour should be grey with light greenish
shade and it should be uniform. Color gives an
indication of excess lime or clay.
3. Float test: A good cement won’t float if you
throw a cement in water.
4. When you put your hand in cement bag you
should feel cool.
Q22. 1BHK full form : 1 Bedroom, 1 Hall, 1kitchen
Q23. What are the Different types of Slabs?
A. There are 16+ different types of slabs –
Q24. What is Initial & final setting time of concrete?
A. Intial Setting time : 30mins, Final setting time : 10hrs
Q25. What is durability?
A. Ability to withstand under pressure is called
Durability.
Q26. What are the concrete tests?
A. Slump test, Compressive strength test, water permeability test, Water absorption test
🚩ይቀጥላል ...
@engineersWorks
.
Q1. What is the Unit Weight of concrete?
A:- The unit weight of concrete depends on the type of aggregates and amount of voids. As per IS : 456-200 Unit weight of PCC is 24KN/m3 and RCC
is 25KN/m3
Q2. What is the unit weight of Steel?
A. The unit weight of Steel is 78.5KN/m3
Q3. What are the Nominal Concrete Mix proportions
for different grades:
A. Important: C-15 - 1:2:4 and C-5 - 1:4:8,C-20 and C-25 - 1:2:3,
(Cement:Sand:aggregate)
Q4. What is ductility?
A. Ductility is the Ability to deform under tensile
stress.
Q5. How to find the weight of steel bar used in
reinforcement?
A. Weight of Bar in kg/m = Dsquare/162.2 D- Dia
of bar in mm
Q6. What’s the difference between one-way slab
and two-way slab?
A. One way slab: Ratio of Longer Span / Shorter
span > 2 Two way slab: Ratio of Longer span/ shorter span <= 2
Q7. What is flat slab?
A. The slab which is supported on columns (Flab slab don’t have beams)
Q8. What do you mean by One storeyed, Two
storeyed building?
A. The building which has two floors is called two
storeyed building.
Q9. What’s the height of each floor?
A. 3m
Q10. What’s the length of rise and tread in Stair
case?
A. Rise – 150mm to 200mm, Tread – 250mm to 300mm
Q11. What’s the slope of Staircase?
A. As per IS 456, the slope or pitch of stair should
be between 25 degrees to 40 degrees.
Q12. What do you mean by the moment of inertia?
A. A quantity expressing a body’s tendency to resist
angular acceleration, which is the sum of the
products of the mass of each particle in the body
with the square of its distance from the axis of
rotation.
Q13. What is a crank length in the slab?
A. The crank length in Slab is 0.42 D. Where D is
Depth of Slab- Top cover – Bottom Cover.
Q14. What are the types of a slump?
A. True Slump: The concrete mass after the test when slumps evenly all around without disintegration is called the true slump.
*Shear Slump: When one-half of the concrete mass
slide down the other is called the shear slump. This type of slump is obtained in a lean concrete mix.
*Collapse Slump: When the sample is collapsed due to adding excessive water, it is known as collapse slump.
*Zero Slump: For very stiff or dry mixes it does not
show any changes of the slump after removing the
slump cone.
Q15. What is honeycomb in concrete? How is it
formed? How to eradicate honey comb in concrete?
A. Learn about Honeycomb concrete –
Q16. What is grouting?
A. Grout is a fluid form of concrete which is used
to fill the voids.
Q17. What is allowable moisture content in Fine
aggregate for the concrete mix?
A. We won’t use the aggregate if its moisture
content is more than 5%.
Q18. What do you mean by segregation?
A. Segregation is a separation of cement, sand from aggregate. This is caused due to Water
cement ratio and when concrete is poured about
more than 1.5m
Q19. What is Seepage?
A. Slow percolation of water through soil is called
Seepage.
Q20. What is the Compressive Strength of brick?
A. Second class brick-70kg/cm2
First class brick-105kg/cm2 Fire brick-125kg/cm2
Q21. How do you check the quality of cement on
the site?
A. 1. Date of Mfg: Cement strength decreases with
its age.
2. Color: Colour should be grey with light greenish
shade and it should be uniform. Color gives an
indication of excess lime or clay.
3. Float test: A good cement won’t float if you
throw a cement in water.
4. When you put your hand in cement bag you
should feel cool.
Q22. 1BHK full form : 1 Bedroom, 1 Hall, 1kitchen
Q23. What are the Different types of Slabs?
A. There are 16+ different types of slabs –
Q24. What is Initial & final setting time of concrete?
A. Intial Setting time : 30mins, Final setting time : 10hrs
Q25. What is durability?
A. Ability to withstand under pressure is called
Durability.
Q26. What are the concrete tests?
A. Slump test, Compressive strength test, water permeability test, Water absorption test
🚩ይቀጥላል ...
@engineersWorks
👉part 2 ከ ቅድም የቀጠለ @engineersWorks
.
Q27. What is bleeding in concrete?
A. Bleeding is one form of segregation, where water
comes out to the surface of the concrete, being
lowest specific gravity among all.
Q28. What is the name of the machine to get
compression test?
A. Universal testing machine (UTM)
Q29. When we go for Pile foundation?
A. Pile foundation is adopted when the Soil bearing capacity is less than 24KN/M3
Q30. What is the function of stirrups in the column?
A. Stirrups are provided to handle the shear force
and to hold the rebars (main bars)
.
CLEAR COVER TO MAIN REINFORCEMENT:
1. FOOTINGS : 50 mm
2. RAFT FOUNDATION.TOP : 50 mm
3. RAFT FOUNDATION.BOTTOM/SIDES : 75 mm
4. STRAP BEAM : 50 mm
5. GRADE SLAB : 20 mm
6. COLUMN : 40 mm
7. SHEAR WALL : 25 mm
8. BEAMS : 25 mm
9. SLABS : 15 mm
10. FLAT SLAB : 20 mm
11. STAIRCASE : 15 mm
12. RET. WALL : 20/ 25 mm on earth
13. WATER RETAINING STRUCTURES : 20/30 mm
.
WEIGHT OF ROD PER METER LENGTH:
DIA WEIGHT PER METER
6mm = 0.222Kg
8mm = 0.395 Kg
10mm = 0.616 Kg
12mm = 0.888 Kg
16mm = 1.578 Kg
20mm = 2.466 Kg
25mm = 3.853 Kg
32mm = 6.313 Kg
40mm = 9.865 Kg
1bag cement-50kg
1feet-0.3048m
1m-3.28ft
1sq.m-10.76sq.f t
1cu.m-35.28cu.ft
.
STANDARD CONVERSION FACTORS
INCH = 25.4 MILLIMETRE
FOOT = 0.3048 METRE
YARD = 0.9144 METRE
MILE = 1.6093 KILOMETER
ACRE = 0.4047 HECTARE
POUND = 0.4536 KILOGRAM
DEGREE FARENHEIT X 5/9 – 32 = DEGREE
CELSIUS
MILLIMETRE= 0.0394 INCH
METRE = 3.2808FOOT
METRE = 1.0936YARD
.
UNIT WEIGHT:
01. Concrete 25 kN/m3
02. Brick 19 kN/m3
03. Steel 7850 Kg/m3
04. Water 1000 Lt/m3
05. Cement 1440 Kg/m3
06. 1Gallon 3.78 Litres
07. Link 8" = 200mm
08. 1 Hectare 2.471 acr(10000m2)
09. 1 Acr 4046.82m2 = 100 cent
👇👇👇👇
@engineersWorks
.
Q27. What is bleeding in concrete?
A. Bleeding is one form of segregation, where water
comes out to the surface of the concrete, being
lowest specific gravity among all.
Q28. What is the name of the machine to get
compression test?
A. Universal testing machine (UTM)
Q29. When we go for Pile foundation?
A. Pile foundation is adopted when the Soil bearing capacity is less than 24KN/M3
Q30. What is the function of stirrups in the column?
A. Stirrups are provided to handle the shear force
and to hold the rebars (main bars)
.
CLEAR COVER TO MAIN REINFORCEMENT:
1. FOOTINGS : 50 mm
2. RAFT FOUNDATION.TOP : 50 mm
3. RAFT FOUNDATION.BOTTOM/SIDES : 75 mm
4. STRAP BEAM : 50 mm
5. GRADE SLAB : 20 mm
6. COLUMN : 40 mm
7. SHEAR WALL : 25 mm
8. BEAMS : 25 mm
9. SLABS : 15 mm
10. FLAT SLAB : 20 mm
11. STAIRCASE : 15 mm
12. RET. WALL : 20/ 25 mm on earth
13. WATER RETAINING STRUCTURES : 20/30 mm
.
WEIGHT OF ROD PER METER LENGTH:
DIA WEIGHT PER METER
6mm = 0.222Kg
8mm = 0.395 Kg
10mm = 0.616 Kg
12mm = 0.888 Kg
16mm = 1.578 Kg
20mm = 2.466 Kg
25mm = 3.853 Kg
32mm = 6.313 Kg
40mm = 9.865 Kg
1bag cement-50kg
1feet-0.3048m
1m-3.28ft
1sq.m-10.76sq.f t
1cu.m-35.28cu.ft
.
STANDARD CONVERSION FACTORS
INCH = 25.4 MILLIMETRE
FOOT = 0.3048 METRE
YARD = 0.9144 METRE
MILE = 1.6093 KILOMETER
ACRE = 0.4047 HECTARE
POUND = 0.4536 KILOGRAM
DEGREE FARENHEIT X 5/9 – 32 = DEGREE
CELSIUS
MILLIMETRE= 0.0394 INCH
METRE = 3.2808FOOT
METRE = 1.0936YARD
.
UNIT WEIGHT:
01. Concrete 25 kN/m3
02. Brick 19 kN/m3
03. Steel 7850 Kg/m3
04. Water 1000 Lt/m3
05. Cement 1440 Kg/m3
06. 1Gallon 3.78 Litres
07. Link 8" = 200mm
08. 1 Hectare 2.471 acr(10000m2)
09. 1 Acr 4046.82m2 = 100 cent
👇👇👇👇
@engineersWorks