What is a rebar coupler?
What is a rebar coupler?Rebar couplers are used in reinforced concrete structures to the connection steel bars that replace a normal rebar lap joints....
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What is a rebar coupler?
Rebar couplers are used in reinforced concrete structures to the connection steel bars that replace a normal rebar lap joints. The rebar couplers are very useful for reinforced concrete structure columns and walls. The rebar coupler comprises a piece of rebar furnished with a string, and a coupler sleeve at the correct end as seen toward an establishment. In development joints, rebar couplers can be utilized to supplant all bits of the rebar experiencing the form work. Rebar couplers are utilized for joining rebars with a full tensions capacity. The closures of bars to be joined are furnished with strings, and the bars are joined utilizing a coupler sleeve that moves the power on the rebar across the association.
Type of rebar coupler
Concrete is one if the most used construction materials in the world today. It can be placed in forms to create almost any shape, or placed in flat slabs thousands of feet long and inches or feet thick, it can be structural columns and beams supporting tall buildings or bridges, or it can be the hull of a boat that floats underneath the bridge and out to sea.
Concrete is a mixture of cement, usually Portland cement, coarse and fine aggregates (think of coarse as gravel and fine as sand, though other materials may be used). When cement is mixed with water and the appropriate aggregates, it becomes plastic (fluid), and it is placed in forms (molds) to create the shape the user is building. Hydration, a reaction between the dry components of the cement and water causes the concrete to set up, or harden into a stone like material that is the foundation (literally) of the construction industry today.
WORKABILITY OF CONCRETE :
The property of concrete which determines the amount of useful internal work ,necessary to produce full compaction i.e workability is the amount of energy to overcome Friction while compacting. Also defined as the relative ease with which concrete can be mixed ,transported, moulded and compacted.
WORKABILITY TESTS:
SLUMP TEST: Slump cone of bottom dia 20cm, top dia 10cm and height 30cm at three layers of conrete .Each layer tamped for 25 times bya standard tamping rod of 16mm diameter and 60 cm length. The subsidence of concrete under gravity in “mm” is SLUMP.
Workability of concrete
Concrete is one if the most used construction materials in the world today. It can be placed in forms to create almost any shape, or placed in flat...
What is the lap length?
It is the length provided to overlap two rebars in order to safely transfer load from one bar to another bar and alternative to this is, to provide mechanical couplers.
What are the general rules for lap length?
For the different diameter of bars
When the bars of different diameters are to be spliced the lap length is calculated considering the smaller diameter bars.
Suppose you are constructing a column, from bottom 20 mm diameter bar is coming and from here 16 mm diameter bar has to be spliced then for calculating lap length 16 mm diameter should be considered and not 20 mm.
What is the minimum lap length?
For direct tension, the straight length of the lapping bar shall not be less than 15d or 20 cm. While in the case of compression lapping should not be less than 24d.
What is the difference between lap length and development length?
Lap length is provided to safely transfer stresses from one bar to another, while development is needed to safely transfer the stresses from steel bar to concrete to make a continuous structure.
Where lap length is provided in column?
The bending moment at the middle portion of the column is zero it means the middle portion of the column is least stressed. Hence, lapping should be provided in the mid-section of the column.
What is Lap Length?
What is the lap length?It is the length provided to overlap two rebars in order to safely transfer load from one bar to another bar and alternative...
Curing plays an important role on strength development and durability of concrete. Curing takes place immediately after concrete placing and finishing, and involves maintenance of desired moisture and temperature conditions, both at depth and near the surface, for extended periods of time. Properly cured concrete has an adequate amount of moisture for continued hydration and development of strength, volume stability, resistance to freezing and thawing, and abrasion and scaling resistance.
The length of adequate curing time is dependent on the following factors:
- Mixture proportions
- Specified strength
- Size and shape of concrete member
- Ambient weather conditions
- Future exposure conditions
Slabs on ground (e.g. pavements, sidewalks, parking lots, driveways, floors, canal linings) and structural concrete (e.g. bridge decks, piers, columns, beams, slabs, small footings, cast-in-place walls, retaining walls) require a minimum curing period of seven days for ambient temperatures above 40 degrees Fahrenheit.
American Concrete Institute (ACI) Committee 301 recommends a minimum curing period corresponding to concrete attaining 70 percent of the specified compressive strength. The often specified seven-day curing commonly corresponds to approximately 70 percent of the specified compressive strengths. The 70 percent strength level can be reached sooner when concrete cures at higher temperatures or when certain cement/admixture combinations are used. Similarly, longer time may be needed for different material combinations and/or lower curing temperatures. For this reason, ACI Committee 308 recommends the following minimum curing periods:
ASTM C 150 Type I cement seven days
ASTM C 150 Type II cement ten days
ASTM C 150 Type III cement three days
ASTM C 150 Type IV or V cement 14 days
ASTM C 595, C 845, C 1157 cements variable
There are three main functions of curing:
1) Maintaining mixing water in concrete during the early hardening process
Ponding and immersion
Ponding is typically used to cure flat surfaces on smaller jobs. Care should be taken to maintain curing water temperature at not more than 20 degrees Fahrenheit cooler than the concrete to prevent cracking due to thermal stresses. Immersion is mainly used in the laboratory for curing concrete test specimens.
Spraying and fogging
Spraying and fogging are used when the ambient temperatures are well above freezing and the humidity is low. Fogging can minimize plastic shrinkage cracking until the concrete attains final set.
Saturated wet coverings
Wet coverings saturated with water should be used after concrete has hardened enough to prevent surface damage. They should be kept constantly wet.
Left in Place Forms
Left in place forms usually provide satisfactory protection against moisture loss for formed concrete surfaces. The forms are usually left in place as long as the construction schedule allows. If the forms are made of wood, they should be kept moist, especially during hot, dry weather.
2) Reducing the loss of mixing water from the surface of the concrete
Covering concrete with impervious paper or plastic sheets
Impervious paper and plastic sheets can be applied on thoroughly wetted concrete. The concrete surface should be hard enough to prevent surface damage from placement activities.
Applying membrane-forming curing compounds
Membrane-forming curing compounds are used to retard or reduce evaporation of moisture from concrete. They can be clear or translucent and white pigmented. White-pigmented compounds are recommended for hot and sunny weather conditions to reflect solar radiation. Curing compounds should be applied immediately after final finishing. Curing compound shall comply with ASTM C3094 or ASTM C13155.
3) Accelerating strength gain using heat and additional moisture
Live steam
Live steam at atmospheric pressure and high-pressure steam in autoclaves are the two methods of steam curing. Steam temperature for live steam at atmospheric pressure should be kept at about 140 degrees Fahrenheit or less until the desired concrete strength is achieved.
Heating coils
Heating coils are usually used as embedded elements near the surface of concrete elements. Their purpose is to protect concrete from freezing during cold weather concreting.
Electrical heated forms or pads
Electrical heated forms or pads are primarily used by precast concrete producers.
Concrete blankets
Concrete insulation blankets are used to cover and insulate concrete surfaces subjected to freezing temperatures during the curing period. The concrete should be hard enough to prevent surface damage when covering with concrete blankets.
Other forms of curing include internal moist curing with lightweight aggregates or absorbent polymer particles. For mass concrete elements (usually thicker than 3 feet), a thermal control plan is usually developed to help control thermal stresses. Additional information can be found in ACI Committee 308 report Guide to Curing Concrete. For specialty concretes, it is recommended to refer to other ACI reports as follows:
- Refractory concrete ACI 547.1R
- Refractory concrete ACI 547.1R
- Insulating concrete ACI 523.1R
- Expansive cement concrete ACI 223
- Roller-compacted concrete ACI 207.5R
- Architectural concrete ACI 303R
- Shotcrete ACI 506.2
- Fiber-reinforced concrete ACI 544.3R
- Vertical slipform construction ACI 313
- Refractory concrete ACI 547.1R
- Insulating concrete ACI 523.1R
- Expansive cement concrete ACI 223
- Roller-compacted concrete ACI 207.5R
- Architectural concrete ACI 303R
- Shotcrete ACI 506.2
- Fiber-reinforced concrete ACI 544.3R
- Vertical slipform construction ACI 313
Curing in either cold or hot weather requires additional attention. In cold weather, some of the procedures include heated enclosures, evaporation reducers, curing compounds, and insulating blankets. The temperature of fresh concrete shall be above 50 degrees Fahrenheit. The curing period for cold weather concrete is longer than the standard period due to reduced rate of strength gain. Compressive strength of concrete cured and maintained at 50 degrees Fahrenheit is expected to gain strength half as quickly as concrete cured at 73 degrees Fahrenheit. In hot weather, curing and protection are critical due to rapid moisture loss from fresh concrete. The curing actually starts before concrete is placed by wetting substrate surfaces with water. Sunscreens, windscreens, fogging, and evaporation retardants can be used for hot weather concrete placements. Since concrete strength gain in hot weather is faster, curing period may be reduced. Additional information can be found in ACI 306.1, Standard Specification for Cold Weather Concreting, ACI 306R, Cold Weather Concreting, ACI 305.1, Specification for Hot Weather Concreting, and ACI 305R, Hot Weather Concreting
Curing Concrete Test Specimens
Curing of concrete test specimens is usually different from concrete placed during construction. American Society for Testing and Materials (ASTM) has developed two standards for making and curing concrete specimens. ASTM C192 is intended for laboratory samples while ASTM C31 is intended for field samples. Both documents provide standardized requirements for making, curing, protecting, and transporting concrete test specimens under field or laboratory conditions, respectively.
ASTM C192 provides procedures for evaluation of different mixtures in laboratory conditions. It is usually used in the initial stage of the project, or for research purposes.
ASTM C31 is used for acceptance testing and can also be used as a decision tool for form or shoring removal. Depending on its intended purpose, the standard defines two curing regimes: standard curing for acceptance testing and field curing for form/shoring removal. Variation in standard curing of test specimens can dramatically affect measured concrete properties. According to the National Ready Mix Concrete Association (NRMCA), strength for concrete air cured for one day followed by 27 days moist cured will be approximately 8 percent lower than for concrete moist cured for the entire period. The strength reduction is 11 percent and 18 percent for concrete specimens initially cured in air for three days and seven days, respectively. For the same air/moist curing combinations, but 100 degrees Fahrenheit air curing temperature, the 28-day strength will be approximately 11 percent, 22 percent, and 26 percent lower, respectively.
Role of Concrete Curing
Curing plays an important role on strength development and durability of concrete. Curing takes place immediately after concrete placing and finishing,...
Why hook is provided in stirrups
- To prevent from buckling of column.
- The main requirement for safety against bond failure is it provide a sufficient extension of the length of the bar beyond the point where the steel is required to develop its yield stress and this length must be at least equal to its development length. However, if the actual available length is inadequate for full development, special anchorages must be provided, such as cogs or hooks or mechanical end plates.
- Hooks are provided for to resist seismic movement.
- To prevent concrete from splitting outward.
- It prevent slippage of steel from the concrete.
- To Keep longitudinal steel bars in position and hold steel tightly.
This civil engineering article provides brief insight about why the hooks are provided in stirrups.
Hook is offered in stirrups for the subsequent purposes:
- To avert buckling of column.
- The major need for protection against bond breakdown as it offers an adequate expansion of the bar length above the point wherein/where the steel is needed to grow its yield stress as well as the length should be as a minimum up to its development length.
- Hooks are offered for to oppose seismic movement.
- To avert concrete from partitioning externally.
- It averts steel slippage from the concrete.
- To maintain longitudinal steel bars in place as well as keep steel firmly.
Why hook is provided in stirrups
Why hook is provided in stirrups- To prevent from buckling of column.- The main requirement for safety against bond failure is it provide a sufficient...
Q.: If reinforcing bars have been stored outside and have a coating of rust, how much rust is acceptable?
A.: Section 12 of ASTM A 615-96a, "Standard Specification for Deformed and Plain Billet Steel Bars for Concrete Reinforcement," says that rust shall not be cause for rejection provided the weight, dimensions, cross-sectional area, and tensile properties of a hand-wire-brushed test specimen aren't less than the ASTM specification requires.
Section 7.4.2 of ACI 318-95, "Building Code Requirements for Structural Concrete," has a similar statement indicating that reinforcement with rust shall be considered satisfactory, provided the minimum dimensions (including height of deformations) and weight of a hand-wire-brushed test specimen aren't less than applicable ASTM specification requirements.
Q: The project inspector is requiring us to wire-brush mill scale and rust off all our rebar. Although the rebar has been at the site for a couple of weeks, we don't think the rust is that heavy or will interfere with the bond between the concrete and steel. Any suggestion? We're tired of brushing rebar.
A: Fortunately, there are a couple of standards to assist you. The ASTM standard specification for deformed steel reinforcement and the Concrete Reinforcing Steel Institute (CRSI) Manual of Standard Practice both give the same information: Reinforcing bars with rust, mill scale, or a combination of both should be considered as satisfactory, provided the minimum dimensions, weight, and height of deformation of a hand-wire-brushed test specimen are not less than the applicable ASTM specification requirements. This inspection criteria recognizes studies that have shown mill scale and rust enhance the bond between concrete and steel. for document Concrete Reinforcing Steel Institute (CRSI) Manual of Standard Practice PDF download.
SNRN 10/13/2020 Admin Bandung Indonesia
Acceptable Rebar Rust | Rust on Reinforcing Steel
Q.: If reinforcing bars have been stored outside and have a coating of rust, how much rust is acceptable?A.: Section 12 of ASTM A 615-96a, "Standard Specification...
Curing plays an important role on strength development and durability of concrete. Curing takes place immediately after concrete placing and finishing, and involves maintenance of desired moisture and temperature conditions, both at depth and near the surface, for extended periods of time. Properly cured concrete has an adequate amount of moisture for continued hydration and development of strength, volume stability, resistance to freezing and thawing, and abrasion and scaling resistance.
The length of adequate curing time is dependent on the following factors:
- Mixture proportions
- Specified strength
- Size and shape of concrete member
- Ambient weather conditions
- Future exposure conditions
Slabs on ground (e.g. pavements, sidewalks, parking lots, driveways, floors, canal linings) and structural concrete (e.g. bridge decks, piers, columns, beams, slabs, small footings, cast-in-place walls, retaining walls) require a minimum curing period of seven days for ambient temperatures above 40 degrees Fahrenheit.
American Concrete Institute (ACI) Committee 301 recommends a minimum curing period corresponding to concrete attaining 70 percent of the specified compressive strength. The often specified seven-day curing commonly corresponds to approximately 70 percent of the specified compressive strengths. The 70 percent strength level can be reached sooner when concrete cures at higher temperatures or when certain cement/admixture combinations are used. Similarly, longer time may be needed for different material combinations and/or lower curing temperatures. For this reason, ACI Committee 308 recommends the following minimum curing periods:
ASTM C 150 Type I cement seven days
ASTM C 150 Type II cement ten days
ASTM C 150 Type III cement three days
ASTM C 150 Type IV or V cement 14 days
ASTM C 595, C 845, C 1157 cements variable
There are three main functions of curing:
1) Maintaining mixing water in concrete during the early hardening process
Ponding and immersion
Ponding is typically used to cure flat surfaces on smaller jobs. Care should be taken to maintain curing water temperature at not more than 20 degrees Fahrenheit cooler than the concrete to prevent cracking due to thermal stresses. Immersion is mainly used in the laboratory for curing concrete test specimens.
Spraying and fogging
Spraying and fogging are used when the ambient temperatures are well above freezing and the humidity is low. Fogging can minimize plastic shrinkage cracking until the concrete attains final set.
Saturated wet coverings
Wet coverings saturated with water should be used after concrete has hardened enough to prevent surface damage. They should be kept constantly wet.
Left in Place Forms
Left in place forms usually provide satisfactory protection against moisture loss for formed concrete surfaces. The forms are usually left in place as long as the construction schedule allows. If the forms are made of wood, they should be kept moist, especially during hot, dry weather.
2) Reducing the loss of mixing water from the surface of the concrete
Covering concrete with impervious paper or plastic sheets
Impervious paper and plastic sheets can be applied on thoroughly wetted concrete. The concrete surface should be hard enough to prevent surface damage from placement activities.
Applying membrane-forming curing compounds
Membrane-forming curing compounds are used to retard or reduce evaporation of moisture from concrete. They can be clear or translucent and white pigmented. White-pigmented compounds are recommended for hot and sunny weather conditions to reflect solar radiation. Curing compounds should be applied immediately after final finishing. Curing compound shall comply with ASTM C3094 or ASTM C13155.
3) Accelerating strength gain using heat and additional moisture
Live steam
Live steam at atmospheric pressure and high-pressure steam in autoclaves are the two methods of steam curing. Steam temperature for live steam at atmospheric pressure should be kept at about 140 degrees Fahrenheit or less until the desired concrete strength is achieved.
Heating coils
Heating coils are usually used as embedded elements near the surface of concrete elements. Their purpose is to protect concrete from freezing during cold weather concreting.
Electrical heated forms or pads
Electrical heated forms or pads are primarily used by precast concrete producers.
Concrete blankets
Concrete insulation blankets are used to cover and insulate concrete surfaces subjected to freezing temperatures during the curing period. The concrete should be hard enough to prevent surface damage when covering with concrete blankets.
Concrete Curing Role
Curing plays an important role on strength development and durability of concrete. Curing takes place immediately after concrete placing and finishing,...
The American Institute of Steel Construction (AISC) is a not-for-profit technical institute and trade association for the use of structural steel in the construction industry of the United States.
AISC publishes the AISC 360 Specification for Structural Steel Buildings, an authoritive volume on steel building structure design that is referenced in all U.S. building codes.
Specification for Structural Steel Buildings provides an integrated treatment of allowable strength design (ASD) and load and resistance factor.
Construction's Specification for Structural Steel Buildings for the first time provides an integrated treatment of Allowable Stress Design (ASD)
The Specification provides the generally applicable requirements for the design and construction of structural steel buildings and other structures. The 2016 edition of the AISC Specification and Commentary supersedes and is an update of the 2010 edition.
Download from Google Drive
File Format : PDF
File Size : 6.09 MB
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Specification for Structural Steel Buildings
The American Institute of Steel Construction (AISC) is a not-for-profit technical institute and trade association for the use of structural steel in...
The Ministry of Land Management, Urban Planning and Construction is a government ministry of Cambodia. The Ministry is responsible for governing land use, urban planning, construction projects, and for the resolution of land use conflicts
Architectural Drawing Department of Land Capital and Province
Sona 3/06/2019 Admin Bandung Indonesia
Department of Land Capital and Province
The Ministry of Land Management, Urban Planning and Construction is a government ministry of Cambodia. The Ministry is responsible...
GENERAL PROVISIONS
These instructions include the following types of work:
- Exterior plasterwork, two-layer and multilayer, for various structures
- Interior plasterwork with water-repellent additives
- Special plasterwork:
• soundproof plasterwork;
• anti-radiation plasterwork;
• heat-insulating plasterwork;
• decorative plasterwork.
Norms for the following types of work must be taken into account:
- Work with concrete - cast-in-place concrete;
- Work with concrete - concrete for precast items;
- Masonry/brickwork;
- Floor-base work.
DOCUMENTATION TO BE SUBMITTED
The following documentation shall be submitted to the Engineer:
- A catalogue of products indicating how they are to be used
- Instructions for using products
- Manufacturers' certificates confirming that products comply with
specifications.
QUALITY ASSURANCE
The quality of finishing work shall comply with the agreed international standards.
Mortar used shall be checked in accordance with the agreed international standards.
MATERIALS
Plasterwork shall be done in accordance with the agreed international standards. The
standards given in those norms are in force as appropriate.
EXECUTION OF WORK
Allowance must be made for correct installation and inspection of all openings, built-in
items, interior sanitary and electrical networks, and other types of work.
All surfaces must be checked for cleanliness.
Smooth bases shall be fully scratched.
Highly-absorbent bases shall be dampened before starting work.
Plasterwork bases (netting) shall be firmly fixed so that they does not sag or bend.
Fastenings shall be strong and no damage from corrosion shall appear.
Plasterwork netting shall overlap at joins by a minimum of 5 cm. Overlaid accessories
protecting corners and edges shall be strictly vertical or horizontal as appropriate for their
locations.
Preparation of bases for plasterwork shall be appropriate for the particular features of the
plasterwork to be done.
Netting must be installed at places where plasterwork borders on door frames or built-in
wooden components.
Steel structures, steel fasteners etc. which are to be incorporated shall be hot-galvanized.
Surfaces of dissimilar metals which come into contact shall be protected against contact
electrolytic corrosion. Sona 2/09/2019 Admin Bandung Indonesia
Plastering Works
GENERAL PROVISIONS
These instructions include the following types of work:
- Exterior plasterwork, two-layer and multilayer,...
