Method statement PCI 33 g ENG khe sang

Contents 1.GENERAL ISSUE MATERIAL 2.1 TECHNICAL REQUIREMENT 2.2 CHECK QUALITY AND MAINTENANCE CONSTRUCTION SEQUENCE 3.1 CONSTRUCTION OF GIRDER CASTING BED 3.2 INSTALL FORMWORK, REINFORCING, VIBRATING COMPACTION 3.3 FABRICATE CONCRETE MIXTURE 3.4 CAST AND TAMP GIRDER CONCRETE 3.5 CURING 3.6 INSTALL ANS STRETCH HIGH STRENGTH STEEL 3.7 CEMENT-GROUTED 3.8 CONCRETE CLOSE ANCHOR HEAD 3.9 CHECK QUALITY AND ACCEPT CHAPTER I GENERAL ISSUES CHARACTERISTICS ON CONSTITUTION OF GIRDER - Length of total girder LTB = 33m - Depth of girder H - Width of girder horseshoe - Web width = 1.65m Bb = 0.65m b1 = 0.25m - Thickness of girder web at girder end b2 = 0.65m - Concrete grade 40 MPa - PC strand bunched cables, each bunched cables include 15 strands 12.7mm - Girder end crossed 65 degree CHAPTER MATERIAL 2.1 TECHNICAL REQUIREMENT 2.1.1 Prestressing tendon - Use the type of strand 12.7mm according to standard ASTM A416, Grade 270: - Diameter : 12.7mm - Area :98.7mm2 - Volume weight :0.775Kg/m - Collapse limit strength : 1860 Mpa - Commercial elastic limit (in proportion with elongation 1%: 1670Mpa 2.1.2 Common iron - Common iron ding of type fy = 400Mpa 2.1.3 Anchor and accessories - Achor male cone, activity ding type QVM 13-15 (Manufacturer: QVM- China ) 2.1.4 Duct - Use standard steel slad of steel pipe has convolution tendon, galvanized anti-rust Duct diameter 80/87 mm - Duct diameter 80/87, internal diameter with error < 2mm 2.1.5 Cement - Type of cement is used for casting girder is But Son cement- PC40 2.1.6 Coarse aggregate- Stone - Use stone at Khe Ban stone pit- Lao Cai Province - Aggregate content of coarse grain must not contain any material react noxiously with Cali in cement 2.1.7 Small quality of aggregate- Sand - Use yellow sand of sand pit Pho Rang – Lao Cai Province 2.1.8 Water for Concrete mixing - Concrete mixing water is water is well water drilled at the site Water not contain contaminant affect concrete quality Absolutely not use sewage that contains mud or grease - PH  & 8.5 - Water is tested to confirm enough standard before being used to cast concrete 2.1.9 Admixture In order to amplify flexibility of concrete mixture uses admixture Sika Viscocrete 3000-20 2.1.10 Lubricant material of formwork - In order to avoid formwork adhesive into concrete needs to lubricate contact surfaces with concrete, lubricating agent ensures the following requirements: + Dismantle formwork easily + Not reduce quality of concrete at contact position with formwork + Not cause crack, shrinkage creates blot at surface of concrete + Do not rust or corrode formwork + Suitable for using method of spray or browse + Not cause fading cement of concrete - Using agent to lubricate formwork 2.2 CHECK QUALITY AND MAINTENANCE 2.2.1 High strength wire steel - Before put into use of each bundled cable, steel strand CĐC is checked adequately contents according to concrete procedure with the following main points: 2.2.1.1 Check documents and certificates of steel 2.2.1.2 Check external surface of steel strand - Check bunched cable - Use eyes to check whether steel is rust, smeary or not, whether is scratched, broken up or not - Use caliper with accuracy < 0.02mm check the geometrical dimension of strand: degree, diameter… - Consider torsion of steel wire in strand, position of wire in steel strand 2.2.1.3 Check experiment of physics-mechanical index of strand has the following points - Measure steel strand glass, area of steel strand - Define breaking force (ton) of strand and tensile strength (Kg/cm2 ) respective elongation - Define tensile strength respective with elongation 1% - Define elastic module E 2.2.1.4 Maintenance of high strength steel - High strength steel is packed carefully to avoid humid air leads to rust In the process of transporting, maintaining, avoid beat heavily, not spoil packing, not contaminate such as: grease, fertilizer, salt and other contaminants - When Loading and unloading, transporting, not let it batter, chafe, drag - Store contain high strength steel must have lean-to, ensure dry, not humid Imported steel is put separately for each spell, chock cable a distance from floor  20cm, not raise bunched cables 2.2.2 Common iron - Common iron has factory certificate, testing ballots have adequately standards on commercial elastic limit, ultimate strength, elongation, cold bending test, welding test - Common iron is imported put separately each spell to avoid mistake when using Protect carefully to avoid rust, not let it adhering noxious contaminants like: fertilizer, grease, salt 2.2.3 Anchor of high strength faggot steel - Test wedge, anchorage is only put into use when it reaches technical requirements - Need to check certificates of anchor when it is imported and when it is used - Check preliminarily anchorage according to the following requirements: + Use eyes to check anchor shape + Watch whether is rust or not + Use rule to measure sizes, data of anchor + Measure squatness between anchor plate and axial line of anchor + Check degree of aeration of hole to pump cement mortar - Accessories of anchor including: anchor cutting board, anchor head, chock and connect ejector of simultaneous mortar, has condition to check, maintain respectively as maintaining high strength steel 2.2.4 Check duct - duct, pipe connecting duct is checked carefully before putting into use, maintain carefully, avoid rust, not let it adhere pollutants or grease, not breaking duct 2.2.5 Cement - Time for maintaining cement not exceed months - Carry out taking sample to check cement quality at the site according to the following items: + Time of starting setting  one hour, finishing setting  10 hours + Stability of criteria + Cement strength - Cement is not tested or have not technical certificates is not used - In the same girder use one type of cement is taken one spell - 2.2.6 Aggregate and sand - Aggregate and sand are carried out checking to estimate test according each spell each kind and fixed period Physics-mechanical criteria on strength, component, contaminant, module etc must ensure according to standard 2.2.7 Other raw material - All raw material is used to fabricate girder ensures technical criteria of project, if meet requirements is allowed to use CHAPTER CONSTRUCTION SEQUENCE 3.1 CONSTRUCTION OF GIRDER CASTING BED - Structure of bottom formwork bed (from above): + Reinforced concrete slab, length 34m, width 0.65m, thickness 0.2m + Aggregate layer thickness 20cm (at end girder thickness 50cm) + Background of soil filling area compaction K90 3.2 INSTALL FORWORK, REINFORCING, VIBRATING COMPACTION - Formwork to cast steel processing girder - Casing formwork and bottom formwork must be flat, straight sizes must be suitable to design requirements - All joints among casing formwork each other, casing formwork with bottom casing, end girder sheet…must have rubber gasket prevent lose cement mortar Contact surface of bottom with bearing need to have rubber gasket to increase vibration when vibrator work Need to use minimum 26 vibrators capacity 1.8kw and penetrating vibrator with diameter smaller than 50 - Installation sequence: * Install bottom formwork * Install beam reinforcement according to construction drawing * Install duct: * Duct faggot steel absolutely tight, not leak cement mortar, clog or reduce pipe diameter during casting concrete * Joints of duct must roll adhesive tape closing joint * In order to ensure accurate position, duct are kept permanently by steel bars 13 weld to locate to ensure not to move during casting concrete, note, should not weld for steel bars with high yield strength and locating bars will must bind Range of steel bar’s locating according to the construction drawing * Allowable error of pipe compared to design < 2mm when putting and < 5mm after casting concrete * Install high strength bunched cables (bunched cables & 4) and install anchor is buried in the concrete according to the construction drawing approved * Install casing formwork - Arrange vibrator: arrange vibrator on the integrated formwork, finishing installing, need to allow vibrator run idly to check girder, check hardness of formwork Avoid the state to annul vibrating force of girder 3.3 FABRICATE CONCRETE MIXTURE 3.3.1 Rate of mixing concrete - Request of pretesting concrete: * Concrete strength 40 Mpa * Small crawling shrinkage * Well-kneaded characteristic, when vibrating is not segregated - Rate of mixing: aggregate mixed with concrete before using is regulated exactly after having test meet demand, agreed by the Supervision Consultant of project 3.3.2 Technical Requirements - Materials such as: water, cement, stone, sand are weighed and measured according to weight Accuracy when determining material not execs the following numbers: - Water, cement :  1% - Stone, sand :  2% - Viscid admixture :  1% - Before casting concrete and during casting concrete for girder, regularly check, adjust weighing and measuring instruments to ensure the accuracy according to requirement - Before starting to mixing concrete of hard concrete bread texture and other allocutions materials is cleaned internal surface of mixing equipments and transport concrete - Time of mixing concrete is defined through test, each time of mixing not exceed minutes - Concrete was mixed according to required quantity Not mix by-band concrete - Test staff regularly monitoring humidity of quality of aggregate to adjust mixing rate (especially note humidity of sand before and during casting concrete) - Temperature of concrete mixing material (sand, stone, cement) limit within 15 oC 2oC 3.3.3 Check concrete mixture 3.3.3.1 Check contraction: - When regulating contraction of concrete at mixing position consider considerable contraction reduction due to transportation, weather - Check contraction at mixing position and girder casting position to check all batches - Concrete contraction: 7.5  2.5cm - In case, contraction has different departure > 2.5cm, recheck humidity of aggregate and readjust mixture composition of concrete suitably 3.3.3.2 Check mixture composition of concrete in each batch: - Test staff, technical officers monitor, check carefully weight and measurement process of mixture composition (cement, sand, stone and admixture) - For first batch allow to increase by 5% quantity of cement to calculate to adherence of cement mortar of agitating machine 3.3.3.3 Take test sample: Each time to cast concrete, take sample groups to check concrete strength according to the following times: days, days, 28 days, each group has samples 3.3.4 Mix concrete - Concrete is mixed by agitating machine 500 litters and supplied by crane and concrete casting bunker 3.4 CAST AND TAMP GIRDER CONCRETE 3.4.1 Works of checking before casting girder concrete - Before casting girder concrete, carry out checking the following issues: - Based on design result of concrete mixture composition rate is approved by Consultant of project - Check at the site quality, quantity of material - Check to adjust weight and measurement equipments - Check the operation situation of machineries in the line, the situation of supplying electricity, water and standby methods (for crane, agitating machine, compressor, concrete pumping machine…) - Check formwork: hardness, clean, grease, size error… - Check steel reinforcement: diameter, distance, position - Check duct high strength bunched cables: diameter, position, steel reinforcement system of position location system - Check adequacy and position accuracy of burying structure - Know the weather condition: rainy, windy, hot… 3.4.2 Cast and tamp concrete - Concrete is casted continuously, only allow to interrupt when facing special situation but not exceed 30 minutes - Time to cast concrete of one girder must fewer than hours - In order to ensure quality of tamped concrete, arrange to tamp completely capacity kind, chart to move girder’s form, combine to tamp with pricking - Cast concrete according to mode of laying one layer from this side to that side by shelf concrete crane run from this girder end to that girder end Vibration compactor operates coordinating closely with section of casting concrete - Tamping concrete at insulator and abdomen, using bottom vibrator and form vibrator Using penetrate vibrator or plate vibrator tamping concrete of horseshoe and upper side of abdomen Measure girder web thickness under 20 cm should form vibrator only operate one alternate side - Test mode must pay special attention to, must assign some people to monitor whether concrete is leaked out of formwork or not, pay attention to tightening loose vibration compactor, check electricity safety during time of casting concrete During casting concrete to consider scaffolding, if formwork there is any discrepancy, stop to cast to deal with timely - During casting concrete, regularly check duct by steel mouse stretching continuously according to order of duct hole from under girder web to upper position, with purpose to check concrete mortar is leaked or not If mouse tool is clean, not adhere mortar and understanding thoroughly at two girder’s end, continue to check the next holes until finishing to cast concrete If it is leaked, it is dealt with by pumping water or stretching continuously until concrete is jelled then it is allowed to stop -Two hours after finishing to cast concrete, continue to use mouse tool to probe transparency of ducts, If realize that there is concrete in the duct, it is dealt with again (perforate concrete and use water to clean) - After finishing casted concrete, sealing mouth of ducts to prevent foreign matters go into - Clean up equipments (concrete mixer, concrete laying truck, girder…) must establish initially to not affect the construction of the following girders 3.5 CURING - External surface of concrete is covered by sackcloth to prevent sunlight, wind, rain, keep humidity and water in the time as follows: If the weather is hot and windy after 3 hours of curing, if the weather is cold  10 hours, - Curing by water continuously in 14 days and nights including pouring water into readily left hole Always ensure the concrete surface to be humid in the time of coalescence - When the surface strength reaches  20Mpa, allow to open formwork (about days after casting concrete) - When concrete strength reaches 90% of design strength, it allows to stretch high strength faggot steel - When concrete strength reaches 100% of design strength and finish to stretching steel only open girder out of formwork and girder sieve 3.6 INSTALL AND STRETCH HIGH STRENGTH STEEL 3.6.1 Preparation before strain steel strand 3.6.1.1 Checking work: - Consider to check carefully and repair immediately defects of concrete - Check concrete strength if it reaches  90% of design strength, it allows to stretch - Check certificate of high strength steel as well as check preliminarily C.Đ.C steel by tools just at the site - Check anchor and consider certificate of anchor - Check error when installing faggot steel C.Đ.C - Check size of each anchor male cone couple synchronously - Check stretching equipment such as: hydraulic jack, pressure chronometer, pressure oil pump, jack calibrating certificate - Define jack factor like friction factor of jack - Check duct provided that it is clean and transparent - Check labor safety work - Check labor force arranging work 3.6.1.2 Preparation: - Prepare quantity of anchor male cone, anchor head adequately for one girder - Prepare adequately quantity of pretested steel (faggot steel & 2) for girder - Prepare adequately of facilities, equipment like: jack, pump, as well as control and measuring equipments 3.6.2 Install high strength faggot steel - In the same girder only use one kind of high strength steel - Cutting C.Đ.C used machine, must not use heat - High strength steel strand needed to maintain to prevent rust of environment humidity - Using “mouse” clearing standard hole to check ducts, if clearing standard hole not pass, it must have special method to overcome immediately - Before grout high strength faggot steel, spray water to clean duct and anchor then clean and absolutely dry by high-pressure water pump and air-compressor 3.6.3 Process of stretching high strength bunched cables Use YCM-YCW250B jack of China to strain steel bunched cables 3.6.3.1 Preparation to measure - Before carrying out strain high strength faggot steel, must create base lines on girder of directions, use gradienter or altometer to measure deformation of girder of direction at girder end cross sections, 1/4L, 1/2L during stretching 3.6.3.2 Process of stretching high strength bunched cables: staggered force PK a, Condition of stretching bunched cables CĐC - When concrete is compacted reaches 90% of design strength and define stretching factor, adjust pressure chronometer - Stretching faggot steels must implement according to method of procedure, not upset and change - In all cases, must ensure jack center coincide with the circle center and wedge b, Stretching order Stretching steel is carried out by jacks (bunched cables & 2) – jack (bunched cables & 4), stretching process is implemented by periods According to the following chart: *Period 1: Stretching braid; + Jack and also stretch steel to force 0.2 PK, check all faggot steel, if there is any wire loose or overlap, return to readjust and then re-stretch to number 0.2 PK ( if not find out anything to need repair, it not return ) + Mark faggot steel ends at cross sections 1-1, 3-3 to measure elongation and cross sections 2-2, 4-4 to measure subsidence quantity of faggot steel with chock hinge Measure numbers 4 (figure) 1    Jack Jack  4 3 34 Girder 33m DÇm 24m   1  2  Jack Jack *Period 2: Stretching according to the following order: + Step 1: two jacks stretch to 0.1 PK, mark to measure elongation + Step 2: Two jacks stretch to 0.2 PK, mark to measure elongation + Step 3: Jack stretch to 0.5 PK and stop Jack stretch to 0.5 PK then stop Measure elongation of faggot steel ends + Step 4: Jack stretch to 0.8 PK and stop Jack stretch to 0.8 PK and stop Measure elongation of faggot steel ends + Step 5: Jack stretch to 1,00 PK and stop Jack stretch to 1,00 PK and stop Measure elongation of faggot steel ends + Step 6: Jack stretch to 1,05 PK and stop Jack stretch to 1,05 PK and stop Measure elongation of faggot steel ends Rest minutes +Step 7: Two jacks return number PK Measure elongation at faggot steel ends - During stretching, continue to measure expansion factor and deformation of girder Compared with design number - Carrying out dragging PK or not will treated at the site by Consultant ( in case, staggered force reaches while elongation not reach, or there is situation of cable parting appears…) 3.6.3.3 Measure bending deflection and lateral deformation of girder - Measure bending deflection: use level gauge to measure bending deflection of girder - Measure lateral deviation of girder: use altometer to measure lateral deformation of girder in the process of stretching 3.6.3.4 Technical requirements of high strength bunched cables stretching process - Hole centerline, jack centerline and anchor centerline when they are stretched, are adjusted to lie on a line - In order to avoid when forcing anchor male cone, it makes scratch or break strand, when install anchor male cone not let strands to be spiral - Not allow to lag anchor for any strand - Jack is on the defined positions to displace jack freely and ensure not affect different auxiliary forces to jack - Check stretching force by chronometer with accuracy 5% Elongation is measured with accuracy 1mm + Error of staggered force of bunched cables  5% + Error of average elongation of bunched cables  5% and separately for each bunched cable 8% 3.6.4 Order of stretching bunched cable and staggered force Data related to stretching process must write down of clean and clear samples: - Chronometer reading value is measured at pump before measuring - Chronometer reading value at each regulated level - Elongation of bunched cables equivalent to each force level - Elongation before and after seating - Tracking sheet is filled in completely and hand over to relating sides to check and evaluate - Order of stretching bunched cables according to regulation of design from bunched cable 1234 Bunched cables CĐC is stretched from girder end Pay attention to when stretching - Force of cable CĐC is written in the drawing is internal force C.Đ.C before seating not deduct loss of jack and anchor - Before stretching bunched cables CĐC is marked by thin paint hachure at seeing easy position and easy measure can discover steel strand that is slide - After seating, abundant section of steel C.Đ.C is cut by machine and thrust out of anchor 30mm 3.4.6 Check jack and pressure chronometer In order ensure jack and measurement instrument reflect accurately factor that is received by bunched cables, periodically check accurate adjustment according to current regulations 3.7 CEMENT-GROUTED 3.7.1 Technical requirement of cement- grouted - Spraying mortar to backfill hole is carried out just after stretching high strength faggot steel latest not exceeds weeks Except for special situation due to technical problem in the process of stretching is agreed by Supervision Consultant - Spraying mortar is kind of cement mortar + water + expansion agent is designed and approved by Consultant - Kind of cement for mixing mortar take the same kind and same spell with kind of cement for casting girder - Mortar is ensured portability in the time of 60 minutes to ensure pump holes 3.7.2 Pump mortar - After all number of faggot steel in a bar was stretched and through checking to determine is to reach quality then carry out using machine to cut steel at external anchor Before pumping mortar, implement to clean duct holes and anchor by cleaning by water and use air compressor of air filtration and dry blow into pipe to pipe transparently, clean and dry - Mortar pump ensure maintain pump pressure stably  kg/cm2 At mortar pumping holes has inlet valve and escape valve When mortar flow out at escape valve has the same adhesiveness with composite is newly closed escape valve and continue to maintain pump pressure  5kg/cm2 in the time of at least is one minute then close valve - In order to avoid the situation of mortar infiltrate from this hole to that hole, carry out pumping low hole first then pump upper hole - In case, pump is choked, spray to clean and restart from the beginning - Take sample at escape orifice to check flexibility of mortar, flexibility reach requirement 13-15 seconds - Check sample strength of mortar at times 7days, 28 days 3.8 CONCRETE CLOSE ANCHOR HEAD - After grouting, carry out to casting concrete to close anchor heads - Anchor head closing concrete is type of concrete was used to cast girder concrete - Before casting concrete to close anchor head, carve the concrete surface and clean rust of anchor head 3.9 CHECK QUALITY AND ACCEPT - Acceptance work is implemented according to regulation of project  ... measuring equipments 3.6.2 Install high strength faggot steel - In the same girder only use one kind of high strength steel - Cutting C.Đ.C used machine, must not use heat - High strength steel... surface strength reaches  20Mpa, allow to open formwork (about days after casting concrete) - When concrete strength reaches 90% of design strength, it allows to stretch high strength faggot steel... characteristic, when vibrating is not segregated - Rate of mixing: aggregate mixed with concrete before using is regulated exactly after having test meet demand, agreed by the Supervision Consultant