8 ASPHALT PLANT MIX v1

VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH ASPHALT PLANT MIX AND EXECUTION OF CONCRETE ASPHALT PAVEMENT 1/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH TABLE OF CONTENTS I EQUIPMENT USED FOR ASPHALT MIX WORK II EXECUTION OF PRIME COAT III EXECUTION OF TACK COAT IV CONSTRUCTION OF ASPHALT CONCRETE LAYERS V SAFENESS AND PROTECTION OF ENVIRONMENT 2/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH EXECUTION OF THE CONCRETE ASPHALT PAVEMENT I Equipment Used for Asphalt Mix Work The contractor will organize an area for Asphalt mixing plant far from residents The area is large enough to favourably mobilize and transport material, asphalt concrete to the site The Contractor shall submit to the Engineer and relevant authorities relating documents prior execution Plant General The mixing plant should be a weigh-batching type (the use of a continuous drum-mixing plant requires the Engineers approval) and shall have a capacity sufficient to supply the finisher on the road continuously when spreading the asphalt mix at normal speed and required thickness The plant shall be so designed, coordinated and operated as to produce a mixture within the job mix tolerances Unless otherwise approved by the Engineer, the plant shall be provided with Automatic or Computer Controlled batching systems with batch print out records The plant must meet the applicable environmental requirements of Vietnam and be in accordance with applicable provisions of Specification section 01700 “Protection of The Environment” Plant Scales Scales for any weigh box or hopper should be of the spring-less dial type, load cell, or as approved by Engineer and shall be of standard make and design accurate to within one-half of one percent of the maximum load that will be required When spring-less dial scales are used, the end of the pointer shall be set close to the face of the dial and shall be of a type that will be free from excessive parallax The scale shall be provided with adjustable pointers for marking the weight of each material to be weighed into the batch The scales shall be substantially constructed, and those that easily get out of adjustment shall be replaced All dials shall be so located that they will be in plain view of the operator at all times Scales for weighing bituminous material shall conform to the specifications for scales for aggregate The value of the minimum graduation in any case shall not be greater than one kilogram Dial scales for weighing the bituminous material shall not have a capacity of more than twice the weight of the material to be weighed and shall read to nearest kilogram Scales shall be approved by the Engineer and shall be checked as often as the Engineer may deem necessary to assure their continued accuracy The Contractor shall provide and have at hand sufficient standard weights for frequent testing of all scales to their full capacity Equipment for Storage of Bituminous Material Tanks for storage of bituminous material shall be equipped for heating the material under effective and positive control at all times to a temperature within the range specified Steel coils, electricity shall accomplish the heating, or other means such that no flame shall come in contact with the heating tank The circulating system for the 3/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH bituminous material shall be of adequate size to ensure proper and continuous circulation during the entire operating period Suitable means shall be provided, either by steam jackets or other insulation, for maintaining the specified temperature of the bituminous material in the pipe lines, meters, weight buckets, spray bars, and other containers of the flow lines Upon approval of the Engineer, bituminous material may be partially heated in the tanks and brought to the specified temperature by means of booster heating equipment between the tanks and the mixer The total storage of the tanks shall be sufficient to provide 10 hours of full operation of the asphalt mixing plant If more then one storage tank is used, they shall be so connected to the circulatory system that each tank can be separately isolated without interference to the circulation of bitumen to the mixer Feeder for Drier A separate feeder shall be provided for each aggregate to be used in the mix Fine aggregate feeders shall be of the belt type Other types may be used, with the Engineer’s approval, only if they are able to deliver wet materials at a constant rate without clogging All feeders shall be calibrated and the gate opening and speed settings for each approved job mix clearly indicated on the gates and on the plant control panel Once established, the feeder settings shall not be altered without the approval of the Engineer Unless approved by the Engineer, a system of “No Flow” switches shall be installed on each aggregate feeder to stop the plant if no material is flowing from the feed bin after 30 seconds The cold feed bins shall have high enough walls and be wide enough depending upon the loading equipment used to prevent intermingling of materials from adjacent bins Drier A rotary drier of any satisfactory design for drying and heating the material aggregate shall be provided The drier shall be capable of drying and heating the mineral aggregate to the specified temperature Screen Plant screens, capable of screening all aggregate to the specified sizes and proportions and having normal capacities slightly in excess of the full capacity of the mixer, shall be provided They shall have an operating efficiency such that the aggregate deposited in any bin shall not contain more than 1.0 percent of oversize or undersize material Bins a) The plant shall include storage bins of sufficient capacity to supply the mixer when it is operating at full capacity b) Bins shall be divided into at least four compartments and shall be arranged to ensure separate and adequate storage of appropriate fractions of the aggregate, not including mineral filler 4/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH c) Each compartment shall be provided with an overflow pipe that shall be of such size and at such location as to prevent any backing up of material into other bins d) Bins shall be so constructed that the gates not leak and samples can be readily obtained Bituminous Control Unit a) An independent weighing scale shall be provided to obtain the proper amount of bituminous material in the mix within the tolerance specified for the job mix b) The liquid bituminous material shall be delivered to the mixer through one or more spray bars, whose individual lengths shall not be less than 75% of the length of the pugmill c) The independent weighing scale shall be fitted with an automatic bitumen pump to ensure consistent batching during asphalt production d) Means of testing the quantity or rate of flow of bituminous material into the mixer shall be provided e) The weighing device shall be designed and constructed to automatically measure the required amount of liquid asphalt into each batch within a tolerance of 0.4% f) The weighing scale shall be so constructed that the weighing setting may be locked and it will automatically reset after the addition of bituminous material into each batch g) The weighing scale shall be calibrated before any asphalt mix is produced to ensure accuracy of batching Re-calibration of the weighing scale shall be conducted when necessary or as directed by the Engineer h) Thermometric Equipment i) An armored thermometer reading from 100 to 200°C shall be fixed in the bituminous feed line at a suitable location near the discharge valve at the mixer unit j) The plant shall be further equipped with either, an approved dial scale mercury-actuated thermometer, and an electric pyrometer, or other approved thermometric instrument so placed at the discharge chute of the drier as to register automatically or indicate the temperature of the heated aggregates A thermocouple or resistance bulb shall be mounted near the bottom of the bin to measure the temperature of the fine aggregate before entering the mixer k) Unless otherwise approved by the Engineer, automatic temperature controls for the plant’s drier burner shall be used The thermocouple used for discharge and for the fine aggregate bin shall be wired to a temperature recording apparatus Charts showing time and temperature from the temperature recording devise will be given to the Engineer daily 5/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH l) Replacement of any thermometer by an approved temperature recording apparatus may be required by the Engineer, and he may further require that the daily temperature charts be filed with him Dust Collector The plant shall be equipped with dust collector so constructed as to waste or return uniformly to the elevator all or any part of the material collected, as directed by the Engineer 10 Control of Mixing Time The plant shall be equipped with a positive means to govern the time of mixing and to maintain it constant unless changed at the direction of the Engineer 11 Electronic Weight Systems with Automatic Ticket Print out (1) General The asphalt plant shall be equipped with one of the following three electronic weight systems capable of automatically printing a delivery ticket: - Automatic batch plant with print out Electronic weight system on hopper beneath a surge or storage bin Electronic weight system on the truck scales The printed delivery ticket shall contain the following information, or as required by the Engineer, as a minimum: Sequential load number Date and time Name or location of plant Type of mix Truck number Gross, tare, net weights or batch weights (as applicable) Accumulated total of mix for that day, as directed by the Engineer Temperature of mix (may be hand recorded) at plant and site Places for location (chainage or station) of where mix was placed Places for signatures (as directed by the Engineer) The ticket shall be printed with an original and at least copies, one of which shall be provided to the Engineer (2) Truck Scales and Weight House The scale shall be of the type which indicates directly the total weight of the loaded truck The scales shall meet the requirements in accordance with this Specification section The scale desk shall be long and wide enough to weigh all axles simultaneously of any haul truck used on the project The truck scale shall periodically be calibrated and certified by the competent authority (State Committee for Measurement and Quality) The weight house shall be completely enclosed, weather proof and with air conditioner/heater There shall be sufficient window opening as directed by the Engineer (3) Automatic Printer System for Batch Plant The batch plant’s automatic printer system shall print the individual weights of aggregate and bituminous material delivered to the pug-mill and the total weight of batches contained in a truckload 6/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH The automatic printer system shall be used only in conjunction with automatic batching and mixing control systems which have been approved by the Engineer In the event of a printer or other equipment failure, hot mix shall not be shipped unless the Engineer provides approval in writing but in no case shall this continue for more than 12 hours 12 Accessibility and Safety Requirements a) Adequate and safe stairways to the mixer platform and guarded ladders to other plant units shall be placed at all points required for accessibility to all plant operations b) Accessibility to the top of truck bodies shall be provided by means of a platform built to the length and height of the truck’s dump body to enable the Engineer to obtain sampling and mixture temperature data c) To facilitate handling, scale calibration equipment, sampling equipment, etc., a hoist or pulley system shall be provided to raise or lower the equipment from the ground to platform or vice versa d) All gears, pulleys, chains, sprockets, and other dangerous moving parts shall be thoroughly guarded and protected e) Ample and unobstructed passage shall be maintained at all times in and around the truck loading space This space shall be kept free from drippings from the mixing platform 13 Weigh Box or Hopper a) The equipment shall include a means to accurately weigh each bin size of aggregate in a weigh box or hopper, suspended on scales, ample in size to hold a full batch without hand raking or running over b) The weigh box or hopper shall be supported on fulcrums and knife edges, so constructed that they will not be easily thrown out of alignment or adjustment c) All edges, ends, and sides of weigh hoppers shall be free from contact with any supporting rods and columns or other equipment that will in any way affect the proper functioning of the hopper d) There shall also be sufficient clearance between hoppers and supporting devices to prevent accumulations of foreign materials e) The discharge gate of the weigh box shall be so that the aggregate will not be segregated when dumped into the mixer and shall close tightly when the box is empty so that no material is allowed to leak into the batch in the mixer during the process of weighing the next batch 14 Mixer a) The batch mixer shall be an approved twin pugmill type capable of producing a uniform mixture within the job-mix tolerances b) It shall be heat-jacketed with steam, hot oil, or other means approved by the Engineer c) It shall be of such design as to permit visual inspection of the mix 7/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH d) The mixer capacity shall be not less than a ton batch and shall be so constructed as to prevent leakage of contents If not enclosed, the mixer box shall be equipped with a dust hood to prevent loss of dust by dispersion e) The mixer shall have an accurate time clock to control the operation of a complete mixing cycle by locking the weigh box gate after the charging of the mixer until the closing of the mixer gate at the completion of the cycle It shall lock the bitumen bucket throughout the dry and wet mixing periods The dry mixing period is defined as the interval of time between opening of the weigh box gate and the start of application of bitumen The wet mixing period is the interval between the time the bituminous material is spread on the aggregate and the time the mixer gate is opened f) The control of the timing shall be flexible and capable of being set at intervals of not more than seconds throughout cycles up to minutes A mechanical batch counter shall be installed as a part of the timing device and shall be so designed as to register only completely mixed batches g) The mixer shall be equipped with a sufficient number of paddles or blades with proper arrangement to produce a proper and uniformly mixed batch h) The clearance of blades from all fixed and moving parts shall not exceed cm except in the case of aggregates having a nominal maximum size of over 2.5 cm, in which case the clearance shall be so adjusted as to prevent undue breakage of the coarse aggregate during the mixing operation 15 Hauling Equipment a) Trucks for hauling bituminous mixtures shall have tight, clean and smooth metal beds that have been sprayed with a minimum amount of soapy water, vegetable, oil, or lime solution to prevent the mixture from adhering to the beds Each load shall be covered with a canvas or other suitable material of such size as to protect the mixture from the weather b) Any truck causing excessive segregation of material by its spring suspension or other contributing factors, or that shows oil leaks in detrimental amounts, or that causes undue delays, shall upon direction of the Engineer be removed from the work until such conditions are corrected c) When necessary, in order that the mixture will be delivered on the road at the specified temperature, truck beds shall be insulated to obtain workable temperature of the mixture and all covers shall be securely fastened 16 Spreading & Finishing Equipment a) The equipment for spreading and finishing shall be approved mechanical, self-powered pavers, capable of spreading and finishing the mixture true to the line, grade, and cross section required on the Drawings or as directed by the Engineer b) The pavers shall be equipped with hoppers and distributing screws of the reversing type to place the mixture evenly in front of 8/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH adjustable screeds They shall be equipped with quick and efficient steering devices and shall have reverse as well as forward traveling speeds c) The pavers shall be equipped with screed controls which can be adjusted for manual, semi-automatic and fully automatic operation, to ensure that a smooth asphalt mat can be placed regardless of irregularities in the surface being paved The automatic screed control device must be able to sense the required grade from either a taut piano wire guideline or a long (length as required by Engineer) sliding ski d) The pavers shall also be equipped with mechanical devices such as equalizing runners, straightedge runners, evener arms, or other compensating devices, to maintain the trueness of grade and to form the edges of the pavement to true lines without the use of stationary side forms e) Pavers shall be equipped with activated screeds, of either the tamping or vibrating type, and devices for heating the screeds to the temperature required for the laying of the mixture without pulling or marring f) If, during construction, it is found that the spreading and finishing equipment in operation leaves surface tracks in the pavement or indented areas or other objectionable irregularities that are not satisfactorily corrected by scheduled operations, the use of such equipment shall be discontinued and other satisfactory spreading and finishing equipment shall be provided by the Contractor 17 Compacting Equipment a) Contractor must provide adequate equipment to compact the asphalt mixture to meet the requirements stipulated under subsection” Manufacture and Production of the Mixture”, and subsection, “Placing the Mixture”, of this Specification section Each paving operation shall have as a minimum: b) One tandem steel wheel roller for breakdown rolling, weighting between 4.5 to 11 tons c) One pneumatic-tired roller for secondary rolling weighting between 14 to 16 tons This roller will have at least smooth, tread tires of equal size and diameter The tires shall be spaced so that the following tires will cover the gaps between adjacent tires The use of wobble-wheeled rollers will not be permitted d) One tandem steel wheel roller for finish rolling, weighting between and 11 tons e) All rollers shall be equipped with a water spraying system which will prevent sticking of the asphalt mixture to the pneumatic or steeltired wheels Petroleum products are not allowed to be used as lubricant on roller wheels to prevent sticking of asphalt mixture f) All rollers must be self propelled The Contractor may use less compaction equipment or other types, subject to the approval of the Engineer Such approval shall not relieve 9/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH from achieving the compaction requirements as stipulated under subsection “Field Quality Control and Testing” of this Specification section II Execution of Prime coat Material requirement Referent standards The following Standards in their latest edition shall be particularly applied to Works covered by this Specification + TCVN 8817-1:2011 requirements + TCVN 8818:2011 Methods Cationic emulsified asphalt – Technical Liquid asphalt - Technical requirements and Test The materials for Prime Coat shall be medium curing cut-back asphalt grade MC-70 The prime coat shall meet the requirements of standard TCVN 74932005 and TCVN 8818-2011 Prime coat shall puchase from the manufacture Requirement of the execution 2.1 Surface preparation Prior to the application of the binder, loose dirt and other objectionable material shall be removed from the surface by means of power broom or blower or both If this does not provide a uniformly clean surface additional sweeping shall be done by hand using stiff brooms Sweeping shall extend at least 20 centimeters beyond each edge of the area to be sprayed Adherent patches of objectionable material shall be removed from the surface by steel scraper or other approved method and where the Engineer so directs the scraped area shall be washed down with water and hand brooms For Prime Coats on Aggregate Base, the final swept surface finish shall consist of a flat, tight, clean mosaic of coarse and fine aggregate, a surface consisting only of fine aggregate shall not be acceptable The Engineer may direct that a light application of water be made just prior to the application of liquid asphalt to facilitate penetration The Engineer will not permit priming when there is free water present on the surface No application of bituminous material shall be undertaken until the pavement has been prepared to the satisfaction of the Engineer To treat the cross fall in accordance with design requirements It is not permitted apply prime coat during high winds, rain, fog or 10/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH length of road being treated The width of the strips shall be sufficient to ensure that this is achieved The bitumen distributor shall start moving no less than meters in advance of the area to be sprayed so as to be travelling at the correct speed when the spray bar reaches the paper strip and this speed shall be maintained until past the intended finishing point of the binder application The strips shall be promptly removed and disposed of in a manner satisfactory to the Engineer Provision shall be made for 10 percent, or such other percentage as may be determined by the Engineer, of the rated capacity of the bitumen distributor to be retained in the tank at the completion of each run, so as to avoid air entertainment within the delivery system and provide for any minor excess in the rate of application The amount of binder used in each sprayer run shall be measured by dipping the distributor binder tank on level ground immediately before and after each run The average binder application rate achieved on each sprayer run, calculated as the volume of binder used divided by the area sprayed, shall lie within + 5% of the rate directed by the Engineer The achieved application rate shall be calculated before any subsequent spray run is made and any necessary adjustments shall be made to ensure that the directed rate of application is maintained in subsequent runs Spraying shall cease immediately if any defect develops in the spraying equipment and shall not recommence until the fault has been rectified Following the spraying of the binder, any areas of pooling or excessive binder shall be continually redistributed across the sprayed surface, until absorption and curing of the binder prevents further movement of the binder A pneumatic tired roller shall be used for this purpose f Maintenance of Tack Coat Tack coat shall be applied only so far in advance of placement of the overlying bituminous course as is necessary to obtain a suitable condition of tackiness The overlaying bituminous course shall be applied before the Tack Coat has lost its tackiness through over-drying, oxidation, wind-blown dust or otherwise While the Tack coat remains uncovered, the Contractor shall protect it from damage and prevent it from coming in contact with traffic g Field Quality Control and Testing A bitumen sample and certificate shall be provided for each delivery of bitumen to the site of the works Samples of the Tack Coat shall be taken from the distributor as directed by the Engineer The bitumen distributor shall be inspected and tested as follows: Prior to the commencement of spraying works on the Contract; For each 20 tons of product as specified; Following any accident or modification to the distributor, or any other occurrence, which in the opinion of the Engineer warrants rechecking 17/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH the distributor The result of the wet sieve testing of the proposed cover aggregate shall be submitted to the Engineer for approval prior to any use of that aggregate A detailed written record of daily surfacing operations, including the location, binder used on each sprayer run, application rates achieved, and area covered shall be made and submitted to the Engineer 18/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH IV Construction of asphalt concrete layers Reference Standards The following current Vietnamese standards or Standards in their latest edition shall be particularly applied to Works covered by this Specification a TCVN 2011 8818- Liquid asphalt – Technical requirements and Test methods TCVN 2011 8819- Hot asphalt concrete pavement – Requirements on construction and acceptance TCVN 2011 8820- Hot asphalt concrete mixture – Design according to Marshall method TCVN 2011 8860- Asphalt concrete – Test methods TCVN 2006 7572- Aggregates for concrete and mortar – Test methods TCVN 8864:2011 Standard test method for measuring road pavement surface roughness using a 3m straight edge TCVN 8865:2011 Method for measuring and assessment roughness by international roughness index (IRI) TCVN 8866:2011 Standard test method for measuring pavement macrotexture depth using a volumetric technique AASHTO T176 Platic fines in graded aggregates and soils by use of the sand equivalent test TCVN 7493:2005 TCVN 7494:2005 TCVN 7504:2005 Bitumen – Technical requirements Bitumen – Method for sampling Bitumen – Test method for determination of adhesion with paving stone AASHTO T324-04 (HMA) Hamburg wheel-track testing of compacted hot – Mix asphalt Material requirements Coarse Aggregate for Asphalt Mixtures The aggregates to be used in the work shall be of such a nature that the asphalt mixture, proportioned in accordance with the job mix formula, will have a retained strength of not less than 75 percent when tested for loss of cohesion resulting from the action of water No aggregate shall be used until the engineer has approved them Materials shall be stockpiled in accordance with the requirements for material storage and the methods of rain tilt and drainage are required Coarse aggregate shall conform to the requirements of this section and shall consist of crushed stone However, the coarse aggregate used for 19/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH any mix type shall be accepted by the Engineer only if it is demonstrated by laboratory trials that all the specified aggregate property requirements given in this Specification section are met and the mix properties specified in Table can be obtained b Fine Aggregate for Asphalt Mixtures Sand to be used for asphalt concrete must be the natural sand, crushed sand or mixture of natural sand and crushed sand Natural sand to be used must be free of organic mixtures (wood, coal ) Crushed sand to be used must be the one crushed from stone with the impaction strength not under the one of the stone for producing the crushed stone When the fine aggregate of crushed stone and natural sand to be used, each material shall be put in separate bucket for mixing under strict control of mixing proportion The physical and mechanical characteristics of the sand shall meet the requirements of Specification project c Filler for Asphalt Mixtures Mineral filler is the product of crushed stone from carbon stone ( calcite limestone, dolomite …) with the compaction strength bigger than 20Mpa, from base slag of the refiner of cement Carbon stone to bu used for produce the filler shall be the clean and free of organic mixtures, with the dust-mud-clay content not excess 5% Filler shall be dry, light and not crumbling and the mineral filler from the mixing plant shall not be used The physical and mechanical characteristics of the filler shall meet the requirements of Specification project d Bituminous Material for Asphalt Mixtures Bituminous material shall be the bituminous grade 60/70, based on the technical regulations in TCVN 7493-2005 and shall be only tested in the labs LAS-XD (having sufficient capacity for conduct 10 testing criteria for the asphalt concrete as regulated in TCVN 7493:2005) Testing shall be carried out as follows: The method and quantity of the asphalt concrete sample shall be in accordance with the standard TCVN 7494:2005 “ Bituminous – Method of tacking sample” Test method: follow the standards from TCVN 7495:2005 and TCVN 7504:2005 e Asphalt Additive An adhesion and anti-stripping agent shall be added to the bituminous material when the Engineer so directs or approves The additive shall be of a type approved by the Engineer and the required percentage of additive shall be thoroughly mixed with the bituminous material in accordance with the manufacturer’s instruction and as directed by the Engineer for such time as is necessary to produce a homogeneous mixture 20/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH f Sources of Supply Approval of sources of supply of aggregate and mineral filler shall be obtained from the Engineer prior to delivery of material Samples of each shall be submitted as directed In selecting sources of aggregate, the contractor shall take into account the bitumen that can be lost by absorption in to aggregate Variations in bitumen content resulting from varying degrees of bitumen absorption by the aggregates will in no way be considered grounds for renegotiating the unit price of the asphalt mixture g Mixes a General Composition of the Mixture The asphalt mixture shall be composed basically of mineral aggregate and bituminous material In some cases, the addition of mineral filler will be necessary to ensure the properties of the bituminous mixture meet the requirements specified in this Specification section b Bitumen Content of the Mix The bitumen content of the mix shall be fixed so that the total bitumen content, considering the loss by aggregate absorption, shall be not less than the minimum value specified The percentage of bitumen actually to be added to the mix will therefore depend on the absorption of the aggregates used and will be fixed by the Engineer with the approval the job-mix formula c Aggregate Component Proportions Aggregate for hot asphalt mixtures shall conform to the limits contained in Table No 1, unless otherwise directed by the Engineer Table No Aggregate Gradation for Hot Asphalt Mixtures according 22 TCN 249 98 Sieve Size (mm) (mm) Percent Passing by Weight AC Surface course BTNC 12.5 25.0 AC binder course BTNC 19 Asplalt concrete hollow BTNR 19 100 100 90-100 19.0 100 90-100 12.5 74-90 60-78 9.5 60-80 50-72 40-70 4.75 34-62 26-56 15-39 2.36 20-48 16-44 2-18 1.18 13-36 12-33 0.6 9-26 8-24 0.30 7-18 5-17 0.15 5-14 4-13 0-10 21/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH d 0.075 4-8 3-7 Percent of Bituminous by weight of aggregate 4.7-6.0 4.5-5.8 4.0-5.0 Adjusting Mix Proportions by Trial Mixes The Contractor shall demonstrate the suitability of all proposed aggregates and proposed mix component proportions by making and testing trial mixes in the laboratory and also by testing trial mixes made in the mixing plant immediately prior to laying of the mix The test required will include gradation, specific gravity and water absorption on the aggregates to be used, as well as other aggregate property tests that may be requested by the Engineer Trial mixes shall then be made from aggregates in the same condition as applies in the mixing plant immediately prior to batching For weigh-batching plants, this means using aggregate samples taken from the plant hot-bins Before the laboratory trials are commenced, a nominal mix recipe appropriate to the proposed mix materials shall be estimated on the basis of theoretical mix design considerations The nominal aggregate blending proportions, bitumen content and added filler content so determined shall then be used as the starting point and reference datum for the mix variations investigated in the laboratory trials and, if accurately estimated, will simplify and improve the accuracy of the trial-and-error testing process required in the laboratory The rut depth test of asphalt concrete is performed with wheel tracking equipment and rubber wheel by Method B in the atmosphere at Frequency of load impact: 26.5±1.0 circles/ minute, equivalent to (53±2.0) times/1 minute e Nominal Added Filler Content Filler (particles passing the 75 micron (No.200) sieve) may be added to the nominal mix to meet criteria contained in this Specification section or as directed by the Engineer The ratio of filler to total bitumen shall not be greater than 1.1 for Asphalt Concrete Surface Course and 1.4 for Asphalt Concrete Binder Course If the mix strength does not meet the specified requirements with a filler/bitumen ratio within these ranges the strength is to be altered by changing to different aggregates f Nominal Bitumen Content The laboratory values of water absorption for the proposed aggregates shall be used to obtain an estimate of the amount of bitumen likely to be absorbed by the combined aggregates in the nominal mix The estimated Bitumen absorption shall be assumed to be 50% of the measured water absorption The absorbed bitumen so calculated shall be taken into consideration in establishing the bitumen content for the 22/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH trial mixes The laboratory trial mixes shall be prepared using Marshall Mix Design procedures For each mix variant to be tried, at least three Marshall samples shall be prepared and tested, and the mix properties shall be calculated on forms approved by the Engineer For economy, the mix proportions may be optimized in such a way that the bitumen content is minimized within the allowable limits specified, but in no circumstances may bitumen content be reduced below the specified lower limit If the mix optimization process described above has required significant interpolation of the test data, so that the finally selected recipe is not coincident with any of those actually tested during the trials, the Engineer may direct that one further trial mix be prepared and tested to confirm the properties of the selected optimum mix By comparing the results of this single confirmatory trial test with those obtained from the trial mix series, further minor adjustment of the selected mix recipe may be required Similarly, during subsequent quality control of the mix, minor modifications of the mix recipe can be based simply on a comparison of the results of single tests (each test involving at least three test specimens) with the mix variable trends established during the earlier laboratory trials The full trial mix procedure described above, involving the testing of at least 15 separate mix variants, generally does not need to be repeated unless there is a major change in the mix materials (e.g change of aggregate type of sources, change of crusher type, change of bitumen type, etc.) g Job Mix Formula Before starting work, the Contractor shall submit to the Engineer a proposed job-mix formula, in writing, for the mixture to be supplied for the Contract The formula so submitted shall stipulate for the mixture the aggregate source, a combined gradation showing a single definite percentage passing each sieve, as well as a percentage of each material to be used in the mix, expressed as percentages by weight of the total mix, a single definite temperature at which the mixture is to be emptied from the mixer, and a single definite temperature at which the mixture is to be delivered on the road, all of which shall fall within the specified ranges of the general composition and temperature limits The proposed formula shall be supported by the laboratory trial mix data and graphs described in this Specification section In approving the job mix, the Engineer at his discretion may use the submitted formula, in whole or in part, or may request the Contractor to perform additional trial mix tests or to investigate alternative aggregates The job mix shall be fixed and subsequent quality of the mix shall be controlled, in terms of the proportions for the various aggregates, as defined above, not in terms of aggregate batching proportions When approving the job-mix formula, the Engineer will nominate the particular aggregates, and their sources, to which the job-mix formula applies 23/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH h Trial Section Following approval of the proposed Job Mix Formula by the Engineer, the Contractor shall place a trial section at a location approved by the Engineer The test section shall be at least 100 meters of full width, full depth pavement unless otherwise agreed to by the Engineer The trial section shall be made using the approved mix design and proposed production and placing equipment and procedures If the trial section fails to conform to the specifications in any respect the necessary adjustments shall be made and the trial repeated Permanent paving work shall not commence until a satisfactory trial has been placed and the Engineer has approved a final Job Mix Formula i Application of Job-Mix Formula and Allowable Tolerance: All mixture furnished shall conform to the job mix formula approved by the Engineer, within the ranges of tolerances specified below: Material compone nts Testing content and frequency Permissible tolerance (%) for grain size ≤0.075 ≤2.36 Testing basis ≥4.75 In comparison with the Testing each aggreate batch from the mixing plant according to be content of the ±2% ±5% ±6% formula of the bill from the asphalt plant computer Aggreate content approved concrete mixture Average of each grain size for all batches ±1% ±2% ±2% ±2% ±5% ±6% in a production day Random test twice per day to calculate the average of the 02 times Asphalt Testing each ±0.3% In comparison 24/ 31 PHUONG THANH TRANCONSIN VRAMP – CONTRACT PACKAGE:RAP/CP6-7 – MAINTENANCE OF NH6 FROM KM78÷KM98 IN HOA BINH batch according to conten the bill from with the the plant asphalt computer content of the Average of all approved batch in a ±0.1% formula of the production day asphalt concret Average of 02 mixture randon test per ±0.3% day Each day the samples shall be taken of the materials and mixture as outlined in this sub-section, “Field Quality Control and Testing” or any further samples, as the Engineer considers necessary for checking the required uniformity of the mixture When unsatisfactory results or changed conditions make it necessary, the Engineer may approve a new job mix Should a change in a material be encountered or should a change in a source of material be made, a new job-mix formula shall be submitted and approved before the mixture containing the new material is produced and delivered Job materials will be rejected if they are found to have voids or other characteristics requiring a bitumen content greater or less than the specified range j Required Mix Properties The Hot Asphalt mixture shall conform to the requirements given in Table No.2 TABLE No Mix Property Requirements Mix properties Surface course BTNC 12.5 Binder course BTNC 19 Hollow asphalt concrete BTNR 19 Total bitumen content : ( % of total mix by weight ) % 4.7-6 4.5-5.8 4.0-5.0 Absorbed bitumen content %