8 ASPHALT PLANT MIX v1

Unlessotherwise approved by the Engineer, the plant shall be provided withAutomatic or Computer Controlled batching systems with batch printout records.. Plant Scales Scales for any weig

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 mobilize andtransport material, asphalt concrete to the site

The Contractor shall submit to the Engineer and relevant authoritiesrelating 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 01700 “Protection of TheEnvironment”

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 the

bituminous material shall be of adequate size to ensure proper andcontinuous 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 storage tank

is used, they shall be so connected to the circulatory system that eachtank can be separately isolated without interference to the circulation

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 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 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 beshipped unless the Engineer provides approval in writing but in no caseshall 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

d) The mixer capacity shall be not less than a 1 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 ofdust 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 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 of

adjustable 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” Manufacture and Production of the Mixture”, and sub-section, “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 weighting between

14 to 16 tons This roller will have at least 7 smooth, tread tires ofequal size and diameter The tires shall be spaced so that thefollowing tires will cover the gaps between adjacent tires The use ofwobble-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 to the approval of the Engineer Such approval shall not relieve

from achieving the compaction requirements as stipulated under section “Field Quality Control and Testing” of this Specification section.

sub-II Execution of Prime coat

The prime coat shall meet the requirements of standard TCVN

7493-2005 and TCVN 8818-2011 Prime coat shall puchase from themanufacture

2 Requirement of the execution

Adherent patches of objectionable material shall be removed from thesurface by steel scraper or other approved method and where theEngineer so directs the scraped area shall be washed down with waterand hand brooms

For Prime Coats on Aggregate Base, the final swept surface finish shallconsist of a flat, tight, clean mosaic of coarse and fine aggregate, asurface consisting only of fine aggregate shall not be acceptable

The Engineer may direct that a light application of water be made justprior 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

It is not permitted apply prime coat during high winds, rain, fog or

Using the sprayer with heating system up to temperature constructionand maintain this temperature throughout the construction process.This sprayer is fixed directly with thermometer to the container andcan be measured from 0 degree to 200 degree.

The container, pipes and tubes used in the maintain or heating thematerials, 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 trialswill be repeated, as directed by the Engineer, whenever the type ofbituminous material or the type of surface changes The rate ofapplication shall be within the range 0.4 – 2.2 liters/m2 and/or asotherwise approved by the Engineer

b Spraying Temperatures

Spraying temperatures for Prime Coat shall comply with Table 1.Spraying temperatures for cut-back asphalt with kerosene contentsdiffering from those listed shall be obtained by interpolation

Table 1 Spraying Temperatures (Prime Coat)

TYPE OF MATERIAL SPRAYING TEMPERATURE RANGEMC-70 grade cutback 70±10O C

c Excessive Heating

Heating quantities in excess of the requirements or prolonged heating

at high temperatures should be avoided

d Application of the Coating

Prior to Commencement of work, the contractor will carry out fieldtrials under the supervision of the Engineer to establish theappropriate application rate and such trials will be repeated, asdirected by the Engineer

The transverse distribution of bitumen application rates produced bythe distributor shall be tested by passing the spray bar over a test arealaid with 25 cm x 25 cm sheets of absorbent material with a binder-proof backing, which are weighed before and after the sprayapplication The difference in weight shall be used in determining thespraying rate actually applied to each sheet and the variation from themean rate for any sheet across the full width sprayed shall not exceed

15 percent

The length of the surface to be sprayed by each run of the distributorshall be measured and marked on the ground For Prime Coats, paint

or string line shall define the boundaries of the area to be sprayed.Bituminous material shall be so applied that a uniform distribution isobtained at all points The uniform application of bituminous material

at the rate instructed shall be made by means of the bitumendistributor bar spray, where the use of the distributor is not practicablefor the application to small areas

The bitumen distributor shall be operated in accordance with theapproved spray chart Pump speed, vehicle speed, bar height andnozzle settings shall be set in accordance with the chart before andduring each spraying operation

Generally, Prime Coat shall be applied in a single spraying operation.However, where slowness of drying is a problem, or where the coatingtends to flow off the surface, the approved quantity of coating may beapplied in two spraying operations, the first coat being allowed to drybefore application of the second

There shall be an overlap of 20 cm along the adjoining edges of sprayruns The sprayed width shall be greater than the specified width oftreatment at the edge of the pavement surface or edge of shoulder toallow for the reduced bitumen rate at the edge where no jet overlapoccurs

Protective strips of building paper or similar non-porous, flexiblematerial shall be spread on the surface at the start and end of eachspray run Flow through the nozzles shall be started and stoppedentirely on the strips, so that all nozzles operate properly on the entirelength 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 inadvance of the area to be sprayed so as to be travelling at the correctspeed when the spray bar reaches the paper strip and this speed shall

be maintained until past the intended finishing point of the binderapplication The strips shall be promptly removed and disposed of in amanner satisfactory to the Engineer

Provision shall be made for 10 percent, or such other percentage asmay be determined by the Engineer, of the rated capacity of thebitumen distributor to be retained in the tank at the completion ofeach run, so as to avoid air entrainment within the delivery systemand provide for any minor excess in the rate of application

The amount of binder used in each sprayer run shall be measured bydipping the distributor binder tank on level ground immediately beforeand after each run

The average binder application rate achieved on each sprayer run,calculated as the volume of binder used divided by the area sprayedshall lie within ± 5% of the rate directed by the Engineer The achievedapplication rate shall be calculated before any subsequent spray run ismade and any necessary adjustments shall be made to ensure that thedirected 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 beenrectified

Following the spraying of the binder, any areas of pooling or excessivebinder shall be continually redistributed across the sprayed surface,until absorption and curing of the binder prevents further movement ofthe binder A pneumatic typed roller shall be used for this purpose

e Maintenance of Prime Coat

The Contractor shall maintain the primed surface to the specifiedstandard until it is overlaid by the subsequent course The subsequentcourse shall be applied only after sufficient time has elapsed to allowthe primer binder to be fully absorbed and to harden, in order to avoidflushing and softening of the subsequent 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 on the traffic, weather, binder and base materials

The primed surface shall not be opened to traffic other than thatnecessary to lay the next course

In exceptional circumstances where it becomes necessary to permittraffic on the primed surface, clean cover aggregate shall be applied

as directed by the Engineer and traffic may be permitted to use thelanes so treated When applying cover aggregate to a treated lanethat adjoins a lane yet to be treated, a strip at least 20 cm wide alongthe adjoining edge shall be left uncovered, or if covered shall beuncovered when the second lane is being prepared for treatment, inorder to permit an overlap of bituminous material as required above.The use of cover aggregate shall be the minimum extent possible

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 asdirected by the 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 thedistributor, whichever is the more frequent;

- Following any accident or modification to the distributor, or anyother occurrence, which in the opinion of the Engineer warrantsrechecking the distributor

The result of the wet sieve testing of the proposed cover aggregateshall be submitted to the Engineer for approval prior to any use of thataggregate

A detailed written record of daily surfacing operations, including thelocation, binder used on each sprayer run, application rates achieved,and area covered shall be made and submitted to the Engineer

III Execution of Tack coat

The emulsified must be uniform after being steadily stirred and thesegregation due to cooling shall not be accepted

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

or blower or both If this does not provide a uniformly clean surfaceadditional sweeping shall be done by hand using stiff brooms.Sweeping shall extend at least 20 centimeters beyond each edge ofthe area to be sprayed.

Adherent patches of objectionable material shall be removed from thesurface by steel scraper or other approved method and where theEngineer so directs the scraped area shall be washed down with waterand hand brooms

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

It is not permitted apply prime coat during high winds, rain, fog orabout to rain

When the prime coat and tack coat are applied, prohibit shall beapplied to all vehicles on the new surface

2.2 Construction Equipment

Equipments used will include brush and or arir compressor, sprayer,equipment for heating bituminous material and tire roller or othermeans to redistribute cut-back

Using the sprayer with heating system up to temperature constructionand maintain this temperature throughout the construction process.This sprayer is fixed directly with thermometer to the container andcan be measured from 0 degree to 200 degree

The container, pipes and tubes used in the maintain or heating thematerials, 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

b Spraying Temperatures

Spraying temperatures for Tack Coat shall comply with Table 4.1(a)below

Table 4.1(a) Spraying Temperatures (Tack Coat)

Type of Material Spraying Temperature

RangeCationic emulsified asphalt CRS-1 20 – 70° C

c Excessive Heating

Heating quantities in excess of the requirements or prolonged heating

at high temperatures should be avoided