METHOD STATEMENT FOR CONSTRUCTION OF COLOUM AND TIE BEAM AT ATI PLANT RENOVATION PROJECT
APPROVAL :
Prepared By, PT. SUKSES KARYA
ABADI
Reviewed By, PT. BEREAU VERITAS
INDONESIA
Acknowledge by, PT. ATOMIZATION TECHNOLOGY INDONESIA
Su Wen
Project Manager Constultant Management Owner
TABLE OF CONTENTS
I. Preliminary 3
II. Scope 3
III. Logistic 4
IV. Stages of Work 4
V. Personil in Charge 18
VI. Safety Construction Measures 18
I. Preliminary :
Coloumb and tie beam are main structural element of building. To make a sturdy building we must pay attention to every method of carrying out the work. The purpose of this method statement is to outline the general construction method for coloumb and tie beam of this project.
II. Scope :
There are two phases of tie beam casting process. The division of the two phases is based on the needs of the MEP work. The first phase is 1-axis until 4-axis and the second phase is 5-axis until 9-axis. After all of the tie beam work finished, continue to the coloumb work with same phase.
III. Logistic :
Casting work uses the following equipment:
1. Safety Helmet 2. Vest
3. Gloves 4. Safety Shoes 5. Excavator
6. Concrete mixer truck 7. Concrete pump truck 8. Vibrator
9. Shovel 10. Hoe
IV. Stage of Work:
1. Formwork of tie beam
Material selection
φ48 steel pipes Φ10 pairs of tension bolts, 15mm thick multi-layer plate, 50mm * 100mm wooden square, steel pipe support system, adjustable U-shaped bracket, etc.
Formwork support and reinforcement method
The side formwork of the beam is reinforced with steel pipe hoops and pull bolts, one every 800mm. Pull up and down in pairs.
2. Formwork of coloumb
Material Selection
φ48 steel pipes Φ10 pairs of tension bolts, 15mm thick multi-layer plate, 50mm * 100mm wooden square, steel pipe support system, adjustable U-shaped bracket, etc.
Coloumb support method
Column formwork design: frame column formwork
The column formwork is made of 15mm thick multi-layer boards. The formwork is prepared according to the cross-sectional size of the column. When preparing the formwork, the large surface is pressed against the small surface. At the interface between the column and the beam, the column formwork is slotted, and the beam side formwork is connected to the groove edge. The joint is tight and tightly pressed with wooden blocks. The column formwork is reinforced with steel pipe hoops and split bolts every 500mm. The hoop is adjusted with bolts; Vertical keel is 50 × 100 square meters of wood, with split bolts φ 10.
Adjusting clamp Bolt
hole for cleaning dirt Flat reinforcement Adjusting clamp
Flat reinforcement Upright panel
Support beam
Upright panel Molded Panel Bolt
Molded panel
3. Formwork Removal
Sequence of formwork removal
a. Before dismantling the formwork, the supervisor in charge of the area must provide a written technical briefing to the construction team, including the dismantling time, sequence, requirements, and stacking location of the formwork.
b. The removal of formwork should follow the principle of first supporting and then dismantling, and then supporting and dismantling; Dismantle the non load-bearing formwork first, and then dismantle the load-bearing formwork; From top to bottom, the support should first remove the lateral support and then the vertical support.
c. The dismantling process of wall and column formwork: loosen the foundation wooden wedges and top supports → remove the split bolts and connectors or column clamps from top to bottom → remove and lift the formwork in pieces → clean and maintain the formwork and accessories.
d. The dismantling process of beam and top plate formwork: First, remove the horizontal tie rods and shear braces of the support part → remove the split bolts and side formwork support of the beam → remove the beam side formwork → lower the top wing support screw of the floor formwork pillar by 2-3cm to lower the formwork → remove the floor formwork, wooden ribs and pillars in sections and sections → remove the beam bottom formwork and support system.
Requirements for dismantling side formwork
The removal of side formwork should be based on the concrete strength to ensure that the removal does not damage the edges and corners, that is, the compressive strength of the concrete
test block under the same conditions reaches 1.2 Mpa at room temperature. Generally, it can be removed 72 hours after the completion of concrete pouring.
Precautions for formwork removal
a. Column formwork: When removing the formwork, first remove the supporting steel pipe, then loosen the hoop to separate the formwork from the column, and gently pry to separate the formwork from the concrete surface. When it is difficult to demould, a crowbar can be used to pry at the bottom. It is strictly prohibited to pry, shake, or use a sledgehammer to hit the formwork at the top. The removed formwork should be cleaned of debris on the formwork and lining mold in a timely manner, and isolation agent should be applied to the panel. After each removal, a comprehensive inspection and maintenance should be carried out. After the pouring of the post pouring concrete is completed, the formwork can only be removed when the strength reaches 90%.
b. When dismantling the formwork, a warning area must be set up and no one is allowed to enter below. Formwork dismantling operators must stand in a stable, firm and reliable place, maintain their own balance, and not pry fiercely to prevent instability and falling.
c. The dismantled formwork support and other materials must be dismantled, cleaned, transported, and stacked at the same time. It is strictly prohibited to throw down materials that are higher than the dismantled floor.
4. Reinforcement engineering
Process flow diagram
a. Column reinforcement binding
Positioning and setting out → Reinforcement correction → Column reinforcement installation → Vertical reinforcement connection → Binding of reinforcement → Inspection and acceptance
b. Floor reinforcement binding
Clean the formwork → Snap the alignment line → Bind the lower layer steel bars → Water and electricity piping → Bind the upper layer steel bars → Check and accept
c. Beam reinforcement binding
Support the beam bottom formwork → Layout the upper and lower steel bars and waist bars of the main reinforcement → Pass through the main reinforcement stirrups and fix them with the upper and lower steel bars of the main beam → Pass through the lower and upper longitudinal bars of the secondary beam → Pass through the upper and lower steel bars of the secondary beam and fix them → Inspection and acceptance.
Key points of the process
a. The steel bars are processed on site and optimized for cutting by computer.
Reinforcement processing includes straightening and rust removal, cutting, bending, and threading with straight threads. The large diameter steel bars are cut using a band saw machine instead of traditional toothless saws, which has fast speed, low mechanical loss, and no damage to the steel bars. Additionally, a new type of straight thread processing machine is used to ensure the quality of joint processing. The steel bar processing is strictly carried out in accordance with the layout results and operating procedures, and advanced processing machinery is used to make the steel bar molding more accurate.
b. The specifications of the connecting sleeve are consistent with the specifications of the steel bars. Before connecting, check whether the steel bar threads and connecting sleeve threads are intact and undamaged. If any quality defects are found, they should be returned for reprocessing. Only after the quality is qualified can they be used. During the steel bar connection process, tighten the joint with a wrench according to the operating procedures. The exposed wire buckle of the steel bar should not exceed one complete buckle. If more than one complete buckle is found, it should be re tightened or the cause should be found and eliminated in a timely manner. When using pre embedded joints, the position, specification, and quantity of the connecting sleeve should meet the design requirements. The steel bars with connecting sleeves are firmly fixed, and the exposed
end of the connecting sleeve is covered with a protective cover. Immediately mark the well connected joints with paint to prevent leakage.
c. Snap the wall position line on the concrete slab and correct the reserved steel bars. First bind 2-4 vertical bars and draw a horizontal bar grading mark. Then position the two horizontal bars at the bottom and chest level, and draw a vertical bar grading mark. Tie the horizontal bars first and then the vertical bars, with the horizontal bars outside and the vertical bars inside. When binding the vertical load-bearing steel bars of the wall, hang them straight before binding them. When binding the steel bars, all the intersections of the steel bars should be firmly tied, and three buckles should be tied at any overlapping point to avoid deformation due to instability. The binding lead wire should be facing inward. When binding wall steel bars, the horizontal bars should be pulled through the line, and the vertical bars should be hung vertically to ensure horizontal and vertical alignment. The positioning of wall steel bars relies on the steel bar spacing frame, which can ensure that the spacing between all wall main bars is accurate and fully in place, ensuring that the protective layer is completely correct. The thickness of the wall protection layer is controlled by using cushion blocks and distance frames to meet the design and specification requirements. The connecting steel bars between the shear wall and the floor support plate are reserved during the binding of the shear wall steel bars.
For the convenience of construction, the reserved steel bars will be bent 90 ° to be flush with the wall.
d. To ensure the spacing between the vertical main bars of the frame column and the thickness of the protective layer, a horizontal positioning column hoop is set at a position 100mm above the bottom elevation of the floor slab (beam). The positioning column hoop can be reused, and its steel bars are made of steel bars one size larger than the column hoop bars.
e. The steel bar arrangement line pops up, first placing the main reinforcement under stress, and then placing the distribution reinforcement. Timely cooperate with the installation of embedded parts, wire ducts, reserved holes, etc. When binding plate steel bars, use a straight or eight shaped buckle. Except for the intersection points of the two outer steel bars, all other points can be tied in a staggered manner. The plate reinforcement is a double-layer bidirectional reinforcement. To ensure the position of the upper reinforcement, a horse stool iron is added between the two layers of reinforcement. The horse stool iron is processed into an "I" shape using HRB400 diameter 16mm steel bars.
Reinforcement binding shall be carried out at different heights on the floor slab according to the requirements of the drawings.
f. When binding the beam reinforcement, the joint position, staggering, anchoring length extending into the middle node, and length extending over the centerline should all comply with the design and specification requirements, and special attention should be paid to the installation sequence of node reinforcement. When the steel bars inside the beam need to be layered, steel bars of the same specification as the main reinforcement and greater than 25 should be used as dividing steel bars. When binding the hoops, the hoops that bind the longitudinal bars on the upper part of the beam should be bound using the buckle method. The overlapping hooks of the hoops should be staggered and bound in the beam. The hook of the hoops should be 135 º and the straight length should be 10d. If a closed hoop is made, the length of the single weld seam should be 10d. The first hoop at the beam end should be set 50mm away from the edge of the column node, and the hoops at the intersection of the beam end and the column should be densified.
The spacing and length of the densified area should meet the design requirements.
5. Connection of steel bars
After the steel bars are processed in the steel bar processing plant, they are transported to the construction site for binding. The joints of the load-bearing steel bars should be set at places
with low stress, and fewer steel bar joints should be set on the same steel bar. The joints of the steel bars should not be set within the dense area of the stirrups at the beam and column ends. When it is impossible to avoid them, high-quality mechanical connection joints that meet the requirements of equal strength should be used, and the percentage of the steel bar joint area should not exceed 50%.
The welded joints of longitudinal stressed steel bars should be staggered with each other. The length of the connection section of the steel bar welded joint is 35d (d is the larger diameter of the welded steel bar) and not less than 500mm. All welded joints with the midpoint of the joint located within the length of the section belong to the same connection section.
The percentage of welded joint area of tensile steel bars located within the same connection section shall not exceed 50%; Compression reinforcement is not limited.
When welding joints are used, beam and plate components should be welded using flash butt welding or lap arc welding. The weld length should be 5d for double-sided welding and 10d for single-sided welding; Column and wall components can be welded using electroslag pressure welding.
The welding rod adopts the E50 series
The steel bars should be firmly bound to each other to prevent loose binding and displacement of the steel bars due to collision and vibration during pouring and compacting of concrete, resulting in exposed steel bars.
When binding steel bars, sufficient protective layer should be left according to the design regulations, and there should be no negative error. A protective layer should be left and a cushion block made of fine aggregate concrete or cement mortar with the same mix ratio should be used to cushion the steel bars. It is strictly prohibited to cushion the steel bars with steel bars or fix them directly on the formwork with iron nails or lead wires.
Steel bars and iron wires should not come into contact with the formwork. If steel bars are erected using iron horse stools, if they cannot be removed, a water stop ring should be welded
on the iron horse stools to prevent water from seeping into the concrete structure along the iron horse stools.
When the arrangement of steel bars is dense, which affects the normal pouring of concrete, measures can be taken in consultation with the designer to ensure the quality of concrete pouring.
6. Concrete engineering
Coagulation and mixing
The concrete is made of commercial concrete, and the project department sends professional technical personnel to the commercial concrete mixing station to supervise and assist the mixing station staff in strictly following the selected construction mix ratio, accurately calculating and weighing each type of material to ensure the quality of raw materials for impermeable concrete. The method of adding admixtures should comply with the usage requirements of the selected admixtures.
Concrete pouring and vibration
a. Before pouring, the position, elevation, and size of the embedded parts should be checked for correctness.
b. Before pouring, the accumulated water, sawdust, iron wire, nails and other debris inside the formwork should be removed, and the formwork should be moistened with water;
And check if the position, elevation, and size of the embedded parts are correct.
c. The height of concrete pouring should not exceed 1.5m, otherwise tools such as tumbling barrels, chutes, or chutes should be used for pouring to prevent stone accumulation and affect quality.
d. If there are dense pipe clusters in the structure, as well as densely embedded parts or steel bars, which are difficult to compact the concrete in real time, fine aggregate concrete of the same impermeability grade should be used for pouring to ensure quality.
e. Concrete pouring should be carried out in layers, with each layer thickness controlled at 30-40cm. The time interval between adjacent layers of pouring should not exceed 1.5h.
f. Waterproof concrete should be mechanically vibrated. Mechanical vibration can generate vibrations with small amplitude and high frequency, reducing the friction and adhesion between aggregates, and increasing the fluidity of cement mortar. The coarse aggregates dispersed due to vibration are fully wrapped by cement mortar during the settlement
process, forming a certain amount and quality of mortar wrapping layer, while extruding bubbles in the concrete mixture, To enhance compactness and impermeability.
g. Mechanical vibration should be carried out in accordance with the relevant provisions of the current "Code for Construction and Acceptance of Concrete Structures", in order to compact and prevent missing or insufficient vibration.
h. Curing of concrete
The maintenance of waterproof concrete has a great impact on its impermeability performance, especially early wet curing, which is more important. Generally, the concrete should be covered when it enters the final set (4-6 hours after pouring), and the wet curing with water should not be less than 14 days. Because under humid conditions, the internal moisture of concrete evaporates slowly, preventing early water loss, which is conducive to cement hydration. Especially in the first 14 days after pouring, the cement hardens quickly, and the strength growth can reach almost 80% of the standard strength of 28 days. Due to sufficient hydration of cement, its products will plug the pores, cut off the capillary pathway, and make the cement stone crystal dense. The strength and impermeability of concrete can be quickly improved; After 14 days, the hydration rate of cement gradually slows down, and the increase in cement content also slows down.
Although continuing maintenance is still beneficial, its impact on quality is not as good as in the early stage. Therefore, attention should be paid to the maintenance of the first 14 days.
7. Construction joint
Construction joints are one of the weak waterproof areas and should be left with no or less construction joints. The concrete of the bottom plate should be continuously poured. Vertical construction joints are not allowed on the wall, and they should be unified with deformation joints. The minimum horizontal construction joint should be no less than 200mm from the
bottom, and no less than 300mm from the edge of the through-wall hole. It should be avoided to be located in the part of the wall panel that bears the maximum bending moment or shear force.
In order to make the joint tight, the surface of the pouring joint should be roughened to remove floating particles. Before continuing to pour concrete, rinse and keep moist with water, and lay a layer of 20-25mm thick cement mortar with the same material and cement sand ratio as the concrete. Continue pouring concrete after compaction.
8. Precautions for pumping waterproof concrete structures
Mix ratio of pumped waterproof concrete
The difficulty of waterproof concrete construction is measured by the "workability" index and slump; The difficulty of pumping concrete construction is measured by its pumpability, which not only depends on the properties of the concrete itself, but also on the influence of factors such as the pressure of the concrete pump, the frictional resistance of the conveying pipeline wall, the resistance of pipeline joints, and the bending part of the pipeline on the performance of the concrete. Therefore, considering the mix ratio of pumped waterproof concrete should be based on achieving excellent pumpability. Due to the fact that pumped concrete is transported through pipelines, in addition to certain requirements for the particle size of stones, it is also necessary to have a certain thickness and good quality mortar wrapping layer around the stones to fully separate them and achieve good fluidity. This is consistent with the principle of ordinary waterproof concrete, so the pumping process can fully meet the requirements of waterproof concrete strength and impermeability. Pumped waterproof concrete can refer to the technical parameters of ordinary waterproof concrete mix proportion, and the following factors should also be considered when selecting the mix proportion:
a. Determine the appropriate sand rate, and the pumping process requires a higher sand rate to achieve good pumpability. Therefore, it may exceed the limit of the sand rate of
waterproof concrete, but it should not be too large. It is advisable to not exceed 50% to avoid affecting the strength and impermeability of waterproof concrete.
b. The slump of pumped waterproof concrete can exceed the 50mm specified in the specifications. According to foreign data, a slump of 50-230mm is within the pumpable range. In fact, if the slump is too small, the mixture will become dry and the frictional resistance inside the pipeline will increase, resulting in poor pumpability; If the slump is too large, the concrete mixture is prone to segregation and bleeding in the conveying pipeline, causing aggregates to accumulate and remain at pipeline joints or bends, forming pipe blockage and affecting pumping. Based on factors such as the performance of concrete raw materials, the transportation distance of concrete mixtures, and the loss of slump, after exploration and trial mixing, the optimal slump of 110-130mm suitable for pumping should be selected without affecting the strength and impermeability of the concrete, ensuring the smooth progress of the pumping process, continuous pouring without leaving construction joints, and achieving good construction results.
c. The maximum particle size of waterproof concrete crushed stone does not exceed 40mm and is also suitable for pumping processes. However, it should be noted that the ratio of the maximum particle size of crushed stone to the inner diameter of the concrete conveying pipeline should be less than or equal to 1:3; Pebbles should be less than or equal to 1:2:5, and the sand passing the 0.315mm sieve should not be less than 15%. This can reduce frictional resistance and extend the concrete delivery pump and delivery time.
The lifespan of the delivery pipeline.
d. It is advisable to add an appropriate amount of additives and fine powder. Adding a water reducing agent can reduce the bleeding rate of fresh concrete, increase the slump of the concrete without increasing the mixing water consumption, increase the fluidity, and allow the stones to advance along the conveying pipeline in the package of high-quality cement mortar, reducing frictional resistance and achieving good pumpability.
e. According to engineering needs, select concrete pump trucks correctly, arrange the positions of pump trucks, distribution rods, and pipelines reasonably, and minimize the number of disassembly and assembly times as much as possible. In general, the closer the pump truck is to the poured structure, the better; The direction of the concrete conveying pipe should be minimized by changing the number of pipes to reduce frictional resistance.
f. Take effective measures to fully supply materials to the concrete pump truck and maintain the continuity of the pump truck's operation. There should be sufficient space to accommodate two mixing trucks after receiving the hopper of the pump truck, and the materials should be supplied through wheel flow to the pump truck; The capacity of the mixer truck to transport concrete should exceed the discharge capacity of the pump truck by 20%.
g. The ratio of the length of the horizontal conveying pipe to the length of the vertical conveying pipe should not be greater than 1:3, otherwise it will lead to an increase in the frictional resistance of the curved part of the pipeline, a decrease in pumpability, and the formation of blockages.
h. The conveying pipeline should be straight, the turning should be slow, and the pipeline joints should be tight without slurry leakage. During construction, it is necessary to prevent air from entering the pipe and forming blockage.
i. Before transporting concrete, the water washing pipe should be pressed first, and then the cement mortar should be pressed. When pressing the first batch of concrete, an additional 100kg of cement can be added to create conditions for smooth pumping.
j. Take measures to prevent large stones and debris from mixing into the concrete mixture.
k. To control the slump, a dedicated person should be assigned to manage and measure it at the mixing plant and on site. Testing should be conducted every 2-3 hours, and the slump value should be adjusted in a timely manner to solve the problem of excessive slump loss that affects pumping.
l. During high-temperature construction, attention should be paid to reducing the temperature of the conveying pipeline. It can be covered with warm grass bags and watered in a timely manner, or wrapped with insulation materials to prevent excessive slump loss and affect pumping.
m. The amount of water required for primary mixing of pumped shrinkage compensating concrete should be determined based on the previously measured slump loss, and secondary water should not be added. Attention should be paid to not allowing transportation and storage time to be too long, as well as controlling the construction temperature.
n. Strengthen the patrol of pump trucks and transportation pipelines, identify hidden dangers, and promptly eliminate them; Shorten the time for dismantling pipelines; Set up a backup pump truck.
o. When the pumping interval may exceed 45 minutes or when concrete segregation occurs, the remaining concrete in the pipeline should be immediately removed with pressure water or other methods.
p. The removed pipeline should be cleaned in a timely manner to prevent increased resistance and blockage during reuse due to cleanliness.
q. After construction, attention should be paid to the maintenance, repair, and storage of mechanical equipment such as pump trucks and pipelines for reuse.
V. Personil in Charge
VI. Safety Construction Measures
All key personel on this section of works shall be unducted into this method statement. Records of attendance at the toolbox meeting shall be kept and filed on site.
This shall be presented at toolbox meetings prior to commencement of these works and then on regular intervals.
Before commencing any work, the safe operation of the related equipment as well as safe work method shall be explained to all personel that are involved at toolbox meeting by the Supervisor / Safety responsible for that area. Any new employee shall be inducted into the operating procedures of that area.
All plant equipment are to be inspected and approved as required by the contract document.