8 asphalt plant mix

SECURITY AND SAFENESS NH91 1 CONSTRUCTION OF TRA NOC BRIDGE; SANG TRANG 1 BRIDGE; SANG TRANG 2 BRIDGE ASPHALT PLANT MIX AND EXECUTION OF CONCRETE ASPHALT PAVEMENT TABLE OF CONTENTS I EQUIPMENT USED FO[.]

ASPHALT PLANT MIX AND EXECUTION OF

CONCRETE ASPHALT PAVEMENT

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

EXECUTION OF THE CONCRETE ASPHALT PAVEMENT

I Equipment Used for Asphalt Mix Work

The contractor will organize an area for Asphalt mixing plant far fromresidents The area is large enough to favourably mobize and transportmaterial, asphalt concrete to the site

- The Contractor shall submit to the Engineer and relevant authouritiesrelating documents prior execution

1 Plant General

The mixing plant should be a weigh-batching type (the use of acontinuous drum-mixing plant requires the Engineers approval) andshall have a capacity sufficient to supply the finisher on the roadcontinuously when spreading the asphalt mix at normal speed andrequired thickness The plant shall be so designed, coordinated andoperated as to produce a mixture within the job mix tolerances Unlessotherwise approved by the Engineer, the plant shall be provided withAutomatic or Computer Controlled batching systems with batch printout records The plant must meet the applicable environmentalrequirements of Vietnam and be in accordance with applicableprovisions of Specification section “1.13 Protection of The Enviroment”

2 Plant Scales

Scales for any weigh box or hopper should be of the spring-less dialtype, load cell, or as approved by Engineer and shall be of standardmake and design accurate to within one-half of one percent of themaximum load that will be required

When spring-less dial scales are used, the end of the pointer shall beset close to the face of the dial and shall be of a type that will be freefrom excessive parallax The scale shall be provided with adjustablepointers for marking the weight of each material to be weighed into thebatch The scales shall be substantially constructed, and those thateasily get out of adjustment shall be replaced All dials shall be solocated that they will be in plain view of the operator at all times

Scales for weighing bituminous material shall conform to thespecifications for scales for aggregate The value of the minimumgraduation in any case shall not be greater than one kilogram Dialscales for weighing the bituminous material shall not have a capacity

of more than twice the weight of the material to be weighed and shallread 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 continuedaccuracy The Contractor shall provide and have at hand sufficientstandard weights for frequent testing of all scales to their full capacity

3 Equipment for Storage of Bituminous Material.

Tanks for storage of bituminous material shall be equipped for heatingthe material under effective and positive control at all times to atemperature within the range specified Steel coils, electricity shallaccomplish the heating, or other means such that no flame shall come

in contact with the heating tank The circulating system for thebituminous material shall be of adequate size to ensure proper and

continuous circulation during the entire operating period Suitablemeans shall be provided, either by steam jackets or other insulation,for maintaining the specified temperature of the bituminous material inthe pipe lines, meters, weight buckets, spray bars, and othercontainers of the flow lines Upon approval of the Engineer, bituminousmaterial may be partially heated in the tanks and brought to thespecified temperature by means of booster heating equipmentbetween the tanks and the mixer.

The total storage of the tanks shall be sufficient to provide 10 hours offull operation of the asphalt mixing plant If more then one storagetank is used, they shall be so connected to the circulatory system thateach tank can be separately isolated without interference to thecirculation of bitumen to the mixer

4 Feeder for Drier

A separate feeder shall be provided for each aggregate to be used inthe mix Fine aggregate feeders shall be of the belt type Other typesmay be used, with the Engineer’s approval, only if they are able todeliver wet materials at a constant rate without clogging

All feeders shall be calibrated and the gate opening and speed settingsfor each approved job mix clearly indicated on the gates and on theplant control panel Once established, the feeder settings shall not bealtered 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 isflowing from the feed bin after 30 seconds

The cold feed bins shall have high enough walls and be wide enoughdepending upon the loading equipment used to prevent intermingling

of materials from adjacent bins

5 Drier

A rotary drier of any satisfactory design for drying and heating thematerial aggregate shall be provided The drier shall be capable ofdrying and heating the mineral aggregate to the specified temperature

6 Screen

Plant screens, capable of screening all aggregate to the specified sizesand proportions and having normal capacities slightly in excess of thefull capacity of the mixer, shall be provided

They shall have an operating efficiency such that the aggregatedeposited in any bin shall not contain more than 1.0 percent ofoversize or undersize material

c) Each compartment shall be provided with an overflow pipe thatshall 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 do not leak and samplescan be readily obtained

8 Bituminous Control Unit

a) An independent weighing scale shall be provided to obtain theproper amount of bituminous material in the mix within thetolerance specified for the job mix

b) The liquid bituminous material shall be delivered to the mixerthrough 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 automaticbitumen pump to ensure consistent batching during asphaltproduction

d) Means of testing the quantity or rate of flow of bituminous materialinto the mixer shall be provided

e) The weighing device shall be designed and constructed toautomatically measure the required amount of liquid asphalt intoeach batch within a tolerance of 0.4%

f) The weighing scale shall be so constructed that the weighing settingmay be locked and it will automatically reset after the addition ofbituminous material into each batch

g) The weighing scale shall be calibrated before any asphalt mix isproduced to ensure accuracy of batching Re-calibration of theweighing scale shall be conducted when necessary or as directed bythe 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 dischargevalve at the mixer unit

j) The plant shall be further equipped with either, an approved dialscale mercury-actuated thermometer, and an electric pyrometer, orother approved thermometric instrument so placed at the dischargechute of the drier as to register automatically or indicate thetemperature of the heated aggregates A thermocouple orresistance bulb shall be mounted near the bottom of the bin tomeasure the temperature of the fine aggregate before entering themixer

k) Unless otherwise approved by the Engineer, automatic temperaturecontrols for the plant’s drier burner shall be used The thermocoupleused for discharge and for the fine aggregate bin shall be wired to atemperature recording apparatus Charts showing time andtemperature from the temperature recording devise will be given tothe Engineer daily

l) Replacement of any thermometer by an approved temperaturerecording apparatus may be required by the Engineer, and he mayfurther require that the daily temperature charts be filed with him.

9 Dust Collector

The plant shall be equipped with dust collector so constructed as towaste or return uniformly to the elevator all or any part of the materialcollected, 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 ofthe Engineer

11 Electronic Weight Systems with Automatic Ticket Print out

(1) General

The asphalt plant shall be equipped with one of the following threeelectronic weight systems capable of automatically printing a deliveryticket:

- Automatic batch plant with print out

- 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:

- Gross, tare, net weights or batch weights (as applicable)

- Accumulated total of mix for that day, as directed by the Engineer

- 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 2 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 inaccordance with this Specification section The scale desk shall be longand wide enough to weigh all axles simultaneously of any haul truckused on the project The truck scale shall periodically be calibrated andcertified by the competent authority (State Committee forMeasurement and Quality) The weight house shall be completelyenclosed, weather proof and with air conditioner/heater There shall besufficient window opening as directed by the Engineer

(3) Automatic Printer System for Batch Plant

The batch plant’s automatic printer system shall print the individualweights of aggregate and bituminous material delivered to the pug-milland the total weight of batches contained in a truckload

The automatic printer system shall be used only in conjunction withautomatic batching and mixing control systems which have beenapproved 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 nocase shall this continue for more than 12 hours

12 Accessibility and Safety Requirements

a) Adequate and safe stairways to the mixer platform and guardedladders to other plant units shall be placed at all points required foraccessibility 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 temperaturedata

c) To facilitate handling, scale calibration equipment, samplingequipment, 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 movingparts shall be thoroughly guarded and protected

e) Ample and unobstructed passage shall be maintained at all times inand around the truck loading space This space shall be kept freefrom drippings from the mixing platform

13 Weigh Box or Hopper

a) The equipment shall include a means to accurately weigh each binsize of aggregate in a weigh box or hopper, suspended on scales,ample in size to hold a full batch without hand raking or runningover

b) The weigh box or hopper shall be supported on fulcrums and knifeedges, so constructed that they will not be easily thrown out ofalignment or adjustment

c) All edges, ends, and sides of weigh hoppers shall be free fromcontact with any supporting rods and columns or other equipmentthat will in any way affect the proper functioning of the hopper d) There shall also be sufficient clearance between hoppers andsupporting devices to prevent accumulations of foreign materials e) The discharge gate of the weigh box shall be so hung that theaggregate will not be segregated when dumped into the mixer andshall close tightly when the box is empty so that no material isallowed to leak into the batch in the mixer during the process ofweighing the next batch

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 thecharging of the mixer until the closing of the mixer gate at thecompletion of the cycle It shall lock the bitumen bucket throughoutthe dry and wet mixing periods The dry mixing period is defined asthe interval of time between opening of the weigh box gate and thestart of application of bitumen The wet mixing period is the intervalbetween the time the bituminous material is spread on theaggregate 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 5 seconds throughout cycles up to 3minutes A mechanical batch counter shall be installed as a part ofthe timing device and shall be so designed as to register onlycompletely mixed batches

g) The mixer shall be equipped with a sufficient number of paddles orblades with proper arrangement to produce a proper and uniformlymixed batch

h) The clearance of blades from all fixed and moving parts shall notexceed 2 cm except in the case of aggregates having a nominalmaximum size of over 2.5 cm, in which case the clearance shall be

so adjusted as to prevent undue breakage of the coarse aggregateduring the mixing operation

15 Hauling Equipment

a) Trucks for hauling bituminous mixtures shall have tight, clean andsmooth metal beds that have been sprayed with a minimumamount of soapy water, vegetable, oil, or lime solution to preventthe mixture from adhering to the beds Each load shall be coveredwith a canvas or other suitable material of such size as to protectthe mixture from the weather

b) Any truck causing excessive segregation of material by its springsuspension or other contributing factors, or that shows oil leaks indetrimental amounts, or that causes undue delays, shall upondirection of the Engineer be removed from the work until suchconditions are corrected

c) When necessary, in order that the mixture will be delivered on theroad at the specified temperature, truck beds shall be insulated toobtain workable temperature of the mixture and all covers shall besecurely fastened

16 Spreading & Finishing Equipment

a) The equipment for spreading and finishing shall be approvedmechanical, self-powered pavers, capable of spreading and finishingthe mixture true to the line, grade, and cross section required onthe 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 ofadjustable screeds They shall be equipped with quick and efficientsteering devices and shall have reverse as well as forward travelingspeeds

c) The pavers shall be equipped with screed controls which can beadjusted for manual, semi-automatic and fully automatic operation,

to ensure that a smooth asphalt mat can be placed regardless ofirregularities in the surface being paved The automatic screedcontrol device must be able to sense the required grade from either

a taut piano wire guideline or a long (length as required byEngineer) sliding ski

d) The pavers shall also be equipped with mechanical devices such asequalizing runners, straightedge runners, evener arms, or othercompensating devices, to maintain the trueness of grade and toform the edges of the pavement to true lines without the use ofstationary side forms

e) Pavers shall be equipped with activated screeds, of either thetamping or vibrating type, and devices for heating the screeds tothe temperature required for the laying of the mixture withoutpulling or marring

f) If, during construction, it is found that the spreading and finishingequipment in operation leaves surface tracks in the pavement orindented areas or other objectionable irregularities that are notsatisfactorily corrected by scheduled operations, the use of suchequipment shall be discontinued and other satisfactory spreadingand finishing equipment shall be provided by the Contractor

17 Compacting Equipment

a) Contractor must provide adequate equipment to compact theasphalt mixture to meet the requirements stipulated under sub-section 3.5,” Manufacture and Production of the Mixture”, and sub-section 3.6, “Placing the Mixture”, of this Specification section Eachpaving operation shall have as a minimum:

b) One tandem steel wheel roller for breakdown rolling, weightingbetween 4.5 to 11 tons

c) One pneumatic-tired roller for secondary rolling This roller will have

at least 7 smooth, tread tires of equal size and diameter The tiresshall be spaced so that the following tires will cover the gapsbetween adjacent tires The use of wobble-wheeled rollers will not

be permitted

d) One tandem steel wheel roller for finish rolling, weighting between 7and 11 tons

e) All rollers shall be equipped with a water spraying system which willprevent sticking of the asphalt mixture to the pneumatic or steel-tired wheels Petroleum products are not allowed to be used aslubricant 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 tothe approval of the Engineer Such approval shall not relieve from achieving thecompaction requirements as stipulated under sub-section 3.7 “Field QualityControl and Testing” of this Specification section

Construction Equipments include as follows:

No Equipment Unit Quantity

4 Asphalt concrete mixing plant 100ton/h each 1

6 Paver Finisher Hydrostatic with sensorcontrol, 100TPH each 1

II Execution of Prime coat

acceptance aggregate base in pavement structure

- The materials for Prime Coat shall be either grade asphalt cement MC-30

or medium curing cut-back asphalt grade MC-70 (conforming to therequirements of ASTM D2027) or Emulsified Asphalt SS-1h, Css-1h(conforming to the requirements of ASTM D97 or ASTM D2397) If materialfor Prime Coat shall be either asphalt cement which is approximatelyequivalent to 60/70 Pen diluted with between 35 and 40 parts of keroseneper one hundred parts of asphalt cement by volume

- The asphalt cement shall conform to 22 TCN 279-2001 standards forviscosity graded asphalt cement The Emulsified Asphalt shall conform to

22 TCN 354-06 for medium curing cut-back asphalt

- When diluted with kerosene, the proportion of kerosene diluents used shall

be as directed by the Engineer

- Where directed by the Engineer, cover aggregate for Prime Coat shall bescreened natural grit or crushed stone, free from weak soft particles,cohesive or organic matter Not less than 98 percent shall pass the 9.5

mm and not more than 2 percent shall pass the 2.36 mm sieve

2 Requirement of the execution

surface by steel scraper or other approved method and where theEngineer so directs the scraped area shall be washed down with waterand hand brooms

consist of a flat, tight, clean mosaic of coarse and fine aggregate, asurface consisting only of fine aggregate shall not be acceptable

prior to the application of liquid asphalt to facilitate penetration TheEngineer will not permit priming when there is free water present onthe surface

- No application of bituminous material shall be undertaken until thepavement has been prepared to the satisfaction of the Engineer

- To treat the cross fall in accordance with design requirements

equipment for heating bituminous material and tire roller or othermeans to redistribute Emulsified Asphalt

and maintain this temperature throughout the construction process

can be measured from 0 degree to 200 degree

materials, are kept clean in good condition and be operated good so asnot to be contaminated by the material outside

2.3 Construction requirements of prime coat

a Rate of Application

The Contractor shall carry out field trials under the supervision of theEngineer to establish the appropriate application rate and such trials will berepeated, as directed by the Engineer, whenever the type of bituminousmaterial or the type of surface changes The rate of application shall be withinthe range 0.4 – 2.2 liters/m2 and/or as otherwise approved by the Engineer

b Spraying Temperatures

Spraying temperatures for Prime Coat shall comply with Table 1 Sprayingtemperatures for cut-back asphalt with kerosene contents differing fromthose listed shall be obtained by interpolation

Table 1 Spraying Temperatures (Prime Coat)

Cutback, more than 100 pph

Note: The abbreviation pph shown in Table 1 means parts of kerosene per

100 parts of asphalt by volume

c Excessive Heating

Heating quantities in excess of the requirements or prolonged heating at hightemperatures should be avoided

d Application of the Coating

Prior to Commencement of work, the contractor will carry out field trialsunder the supervision of the Engineer to establish the appropriate applicationrate and such trials will be repeated, as directed by the Engineer

The transverse distribution of bitumen application rates produced by the

distributor shall be tested by passing the spray bar over a test area laid with

25 cm x 25 cm sheets of absorbent material with a binder-proof backing,which are weighed before and after the spray application The difference inweight shall be used in determining the spraying rate actually applied to eachsheet and the variation from the mean rate for any sheet across the full widthsprayed shall not exceed 15 percent

The length of the surface to be sprayed by each run of the distributor shall bemeasured and marked on the ground For Prime Coats, paint or string lineshall define the boundaries of the area to be sprayed

Bituminous material shall be so applied that a uniform distribution is obtained

at all points The uniform application of bituminous material at the rateinstructed shall be made by means of the bitumen distributor bar spray,where the use of the distributor is not practicable for the application to smallareas

The bitumen distributor shall be operated in accordance with the approvedspray chart Pump speed, vehicle speed, bar height and nozzle settings shall

be set in accordance with the chart before and during each sprayingoperation

Generally, Prime Coat shall be applied in a single spraying operation.However, where slowness of drying is a problem, or where the coating tends

to flow off the surface, the approved quantity of coating may be applied intwo spraying operations, the first coat being allowed to dry before application

of the second

There shall be an overlap of 20 cm along the adjoining edges of spray runs.The sprayed width shall be greater than the specified width of treatment atthe edge of the pavement surface or edge of shoulder to allow for thereduced bitumen rate at the edge where no jet overlap occurs

Protective strips of building paper or similar non-porous, flexible material shall

be spread on the surface at the start and end of each spray run Flow throughthe nozzles shall be started and stopped entirely on the strips, so that allnozzles operate properly on the entire 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 5 meters in advance

of the area to be sprayed so as to be travelling at the correct speed when thespray bar reaches the paper strip and this speed shall be maintained untilpast 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 bedetermined 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 airentrainment within the delivery system and provide for any minor excess inthe rate of application

The amount of binder used in each sprayer run shall be measured by dippingthe distributor binder tank on level ground immediately before and after eachrun

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 necessaryadjustments shall be made to ensure that the directed rate of application ismaintained in subsequent runs

Spraying shall cease immediately if any defect develops in the sprayingequipment and shall not recommence until the fault has been rectified

Following the spraying of the binder, any areas of pooling or excessive bindershall be continually redistributed across the sprayed surface, until absorptionand curing of the binder prevents further movement of the binder Apneumatic typed roller shall be used for this purpose

e Maintenance of Prime Coat

The Contractor shall maintain the primed surface to the specified standarduntil it is overlaid by the subsequent course The subsequent course shall beapplied only after sufficient time has elapsed to allow the primer binder to befully absorbed and to harden, in order to avoid flushing and softening of thesubsequent course

The delay period, which shall be as directed by the Engineer, shall be aminimum of two and generally not more than fourteen days, depending onthe traffic, weather, binder and base materials

The primed surface shall not be opened to traffic other than that necessary tolay the next course

In exceptional circumstances where it becomes necessary to permit traffic onthe primed surface, clean cover aggregate shall be applied as directed by theEngineer and traffic may be permitted to use the lanes so treated When

applying cover aggregate to a treated lane that adjoins a lane yet to betreated, a strip at least 20 cm wide along the adjoining edge shall be leftuncovered, or if covered shall be uncovered when the second lane is beingprepared for treatment, in order to permit an overlap of bituminous material

as required above The use of cover aggregate shall be the minimum extentpossible

f Field Quality Control and Testing

A bitumen sample and certificate shall be provided for each delivery ofbitumen to the site of the works

Samples of the Prime Coat shall be taken from the distributor as directed bythe Engineer

The bitumen distributor shall be inspected and tested as follows:

Prior to the commencement of spraying works on the Contract;

Every 6 months or every 150,000 liters of binder sprayed by the distributor,whichever is the more frequent;

Following any accident or modification to the distributor, or any otheroccurrence, which in the opinion of the Engineer warrants rechecking thedistributor

The result of the wet sieve testing of the proposed cover aggregate shall besubmitted 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 areacovered shall be made and submitted to the Engineer

III Execution of Tack coat

1 Material requirement

Referent standards

The following Standards in their latest edition shall be particularly applied toWorks covered by this Specification

- 22 TCN 279 -01 Specification for bituminous material testing

- 22 TCN 231 -96 Sampling of bituminous material (at supplyresource)

- 22 TCN 354 -06 Cationic Emulsified Asphalt

- 22 TCN 334 -06 Execution and Acceptance for aggregate base andsub-base

2 Requirement of the execution

2.1 Surface preparation

Prior to the application of the binder, loose dirt and other objectionablematerial shall be removed from the surface by means of power broom orblower or both If this does not provide a uniformly clean surface additionalsweeping shall be done by hand using stiff brooms Sweeping shall extend atleast 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 directsthe scraped area shall be washed down with water and hand brooms

No application of bituminous material shall be undertaken until the pavementhas 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 about torain

When the prime coat and tack coat are applied, prohibit shall be applied to allvehicles on the new surface

2.2 Construction Equipment

equipment for heating bituminous material and tire roller or othermeans to redistribute cut-back

and maintain this temperature throughout the construction process

can be measured from 0 degree to 200 degree

materials, are kept clean in good condition and be operated good so asnot to be contaminated by the material outside

2.3 Construction requirements of tack coat

a Rate of Application

The Contractor shall carry out field trials under the supervision of theEngineer to establish appropriate application rate and such trials will berepeated, as directed by the Engineer, whenever the type of surface to becoated, or the type of bituminous material, changes The rate of applicationshall be within the range indicated of 0.1 to 0.7 lit/m2, or as approved by theEngineer