Tài liệu SECTION 05100 PRIME COAT pdf

SUBMITTALS The Contractor shall provide the Engineer with the following: a A 5-litre sample of any bituminous material that the Contractor proposes to use in the work, together with a ce

SECTION 05100 - PRIME COAT

TABLE OF CONTENTS

1 DESCRIPTION 1

2 REFERENCE STANDARDS FOR PRIME COAT 1

3 MATERIALS FOR PRIME COAT 1

4 SUBMITTALS 2

5 CONSTRUCTION REQUIREMENTS 2

5.1 Surface Condition and Weather Limitation 2

5.2 Quality of Work and Rectification of Unsatisfactory Work 2

6 WORK CONDITIONS 3

7 SURFACE PREPARATION 3

8 RATE AND TEMPERATURE OF APPLICATION 4

8.1 Rate of Application 4

8.2 Spraying Temperatures 4

8.3 Excessive Heating 4

8.4 Precautions 5

8.5 Application of the Coating 5

9 MAINTENANCE OF PRIME COAT 6

10 FIELD QUALITY CONTROL AND TESTING 7

11 EQUIPMENT 8

11.1 General 8

11.2 Distributor Capacity 8

11.3 Distributor Application 8

11.4 Distributor Spray Bars and Spreading Equipment 8

11.5 Instrumentation/Calibration 9

11.6 Spray Chart and Operations Manual 9

11.7 Unacceptable Equipment 9

12 MEASUREMENT AND PAYMENT 10

12.1 Measurement for Payment 10

12.2 Measurement of Rectified Work 10

12.3 Basis of Payment 10

SECTION 05100 - PRIME COAT

1 DESCRIPTION

(a) Prime Coat furnished and applied by the Contractor shall conform to the requirements and procedures provided in this Specification section

(b) The work shall consist of furnishing and applying liquid asphalt to previously prepared and approved absorbent surfaces (subgrade, granular subbase or aggregate base course) immediately prior to placing superimposed construction in accordance with the Specification requirements Prime Coat shall be applied to the full width indicated on the Drawings, or as required by field conditions Such work shall be performed

as specified herein or as directed by the Engineer

2 REFERENCE STANDARDS FOR PRIME COAT

The latest printing of the following standards and tests shall apply to Prime Coat

♦ AASHTO M 82 Cut-back Asphalt Medium Curing type

♦ AASHTO M 140 Anionic Emulsified Asphalt

♦ AASHTO M 208 Cationic Emulsified Asphalt

♦ AASHTO M 226 Viscosity Graded Asphalt Cement

♦ AASHTO T 179 Effect of Heat and Air on Asphalt Materials

(Thin-film Oven Test)

3 MATERIALS FOR PRIME COAT

(a) The materials for Prime Coat shall be either AC-20 grade asphalt cement (which is approximately equivalent to 60/70 Pen.) diluted with kerosene or medium curing cut-back asphalt grade MC-70

(b) The AC-20 grade asphalt cement shall conform to AASHTO M 226 standard for viscosity graded asphalt cement The MC-70 shall conform to AASHTO

M 82 for medium curing cut-back asphalt

(c) When AC-20 is to be diluted with kerosene, the proportion of kerosene dilutent used shall be as directed by the Engineer

(d) Cover aggregate for Prime Coat shall be screened 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 ASTM sieve and not more than 2 percent shall pass the 2.36 mm (No 8) sieve

4 SUBMITTALS

The Contractor shall provide the Engineer with the following:

(a) A 5-litre sample of any bituminous material that the Contractor proposes to use in the work, together with a certificate from the Manufacturer, shall be submitted before construction begins The certificate must state that the binder complies with the relevant specification and grade requirements for the prime coat, given in this Specification section

(b) A satisfactory record of the calibration certificates of all instruments, gauges and the dipstick for the bitumen distributor, shall be submitted not less than

30 days before construction begins The dipstick instrument and gauges shall be calibrated, the accuracy shall be shown in the calibration certificate and the date of calibration shall be no longer than two years before the start

of construction

(c) Spray chart, meeting the requirement of sub-section 11.6 of this Specification section shall be submitted before construction begins, so that equipment checks can be carried out

(d) Samples of materials used in each day’s work shall be submitted Daily records of sealing works done and material application rates shall be submitted in accordance with this Specification section, the Drawings or as directed by the Engineer

5 CONSTRUCTION REQUIREMENTS

Prime Coat shall be applied only on surfaces, which are dry or slightly moist Prime Coat shall not be applied during high winds, rain, foggy weather or if rain threatens

(a) The finished coat shall completely cover the area treated and be of uniform appearance, without missed areas or streaks or “rich” areas of accumulated bitumen

(b) After curing for four to six hours, the binder shall have soaked into the base course, leaving behind only sufficient binder to ensure that the surface is uniformly black or dark grey in color and non-porous The texture of the

base course aggregate surface shall be discernable and there must be no pools or films of binder or binder mixed with aggregate fines thick enough

to scrape off the surface with a knife

(c) Rectification of unsatisfactory Prime Coat shall be as directed by the Engineer and may include removal of excess material, the use of cover aggregate, or the application of additional coatings as required Minor potholing of a Prime Coat shall be promptly patched The Engineer may require widespread potholing or other damage to be rectified by scarifying and recompaction or replacement of the base layer followed by re-application of the Prime Coat

6 WORK CONDITIONS

(a) The work shall be carried out in such a manner as to offer the least inconvenience to traffic and without damage to the work

(b) The surfaces of structures or trees or property adjacent to the areas being treated shall be protected so as to prevent their being marred or spattered (c) No bituminous material shall be discharged into any side ditch or drain (d) The Contractor shall provide and maintain at the heating site, adequate fire prevention and control measures, and also first aid supplies and facilities (e) The Contractor shall be responsible for all the consequences of traffic being admitted too early to newly laid Prime Coat, and he shall prohibit such traffic when necessary by the provision of a detour or by half-width construction

7 SURFACE PREPARATION

(a) 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

(b) 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

(c) 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

(d) 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 (e) No application of bituminous material shall be undertaken until the pavement has been prepared to the satisfaction of the Engineer

8 RATE AND TEMPERATURE OF APPLICATION

The Contractor shall carry out field trials under the supervision of the Engineer to establish the appropriate application rate and such trials will be repeated, as directed by the Engineer, whenever the type of bituminous material or the type of surface changes The rate of application shall be within the range 0.45 – 2.25 liters/m2 and/or as otherwise approved by the Engineer

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

TABLE 1

Spraying Temperatures (Prime Coat)

Cutback, 50 pph kerosene (MC-70 grade cutback)

70 + 100 C

Cutback, 75 pph kerosene (MC-30 grade cutback)

45 + 100 C

Cutback, 100 pph kerosene 30 + 100C Cutback, more than 100 pph

kerosene

Not heated

Note: The abbreviation pph shown in Table 1 means parts of kerosene per 100

parts of asphalt cement by volume

Heating quantities in excess of the requirements or prolonged heating at high temperatures should be avoided Any material which, in the opinion of the

Engineer, has been damaged by overheating shall be rejected and shall be replaced at the Contractor’s expense

Extreme care should be used when heating any cut back asphalt cement Open flames or sparks must not be permitted close to these materials Controlled heat should be applied in heating kettles, mixers, distributors or other equipment designed and approved for the purpose Open flames must not be used to inspect

or examine drums, tank cars or other containers in which these materials have been stored All vehicles transporting these materials must be properly vented Only experienced personnel must be permitted to supervise the handling of these materials

(a) The length of the surface to be sprayed by each run of the distributor shall

be measured and marked on the ground For Prime Coats, paint or string line shall define the boundaries of the area to be sprayed

(b) Bituminous material shall be so applied that a uniform distribution is obtained at all points The uniform application of bituminous material at the rate instructed shall be made by means of the bitumen distributor bar spray, except where the use of the distributor is not practicable for the application

to small areas, the Engineer may then approve the limited use of hand spray equipment

(c) The bitumen distributor shall be operated in accordance with the approved spray chart Pump speed, vehicle speed, bar height and nozzle settings shall

be set in accordance with the chart before and during each spraying operation

(d) 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 in two spraying operations, the first coat being allowed to dry before application of the second

(e) When directed, the bituminous material shall be applied in spray runs of approximately one half or less of the width of the completed surface and when so applied there shall be an overlap of 20 cm along the adjoining edges The sprayed width shall be greater than the specified width of treatment at the edge of the pavement surface or edge of shoulder to allow for the reduced bitumen rate at the edge where no jet overlap occurs

(f) 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 through the nozzles shall be started and stopped entirely on the strips, so that all nozzles operate properly on the entire length of road being treated The width of the strips shall be sufficient to ensure that this is achieved (g) 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 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

(h) 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

(i) 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

(j) The average binder application rate achieved on each sprayer run, calculated as the volume of binder used divided by the product of the number of nozzles in use and the spacing between nozzles, 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

(k) Spraying shall cease immediately if any defect develops in the spraying equipment and shall not recommence until the fault has been rectified

(l) 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 typed roller shall be used for this purpose

9 MAINTENANCE OF PRIME COAT

(a) The Contractor shall maintain the primed surface to the specified standard until it is overlaid by the subsequent course The subsequent course shall be applied only after sufficient time has elapsed to allow the primer binder to

be fully absorbed and to harden, in order to avoid flushing and softening of the subsequent course

(b) The delay period, which shall be as directed by the Engineer, shall be a minimum of two and generally not more than fourteen days, depending on the traffic, weather, binder and base materials

(c) Traffic shall not be permitted on the primed surface until the bituminous material has penetrated and dried and, in the opinion of the Engineer, will not pick up under traffic In exceptional circumstances where it becomes necessary to permit traffic prior to that time, but in no case sooner than four hours after the application of the bituminous material, clean cover aggregate shall be applied as directed by the Engineer and traffic may be permitted to use the lanes so treated Cover aggregate shall be spread from trucks in such

a manner that no wheel will travel on uncovered wet bituminous material When applying cover aggregate to a treated lane that adjoins a lane yet to be treated, a strip at least 20 cm wide along the adjoining edge shall be left uncovered, or if covered shall be uncovered when the second lane is being prepared for treatment, in order to permit an overlap of bituminous material

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

10 FIELD QUALITY CONTROL AND TESTING

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

(b) Samples of the Prime Coat shall be taken from the distributor as directed by the Engineer

(c) 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 other occurrence, which in the opinion of the Engineer warrants rechecking the distributor

(d) 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

(e) 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

11 EQUIPMENT

The equipment used by the Contractor shall include a power broom and/or a power blower, a pressurized bitumen distributor, equipment for heating bituminous material and, for Prime Coat work, a pneumatic tired roller or other means of dispersing excess primer binder The Engineer will not permit the use of gravity distributors

The distributor shall have a minimum capacity of 1,000 litters

(a) The distributor shall be so designed, equipped, maintained and operated that bituminous material at even heat may be applied uniformly on variable widths of surface, at a controlled rate of transverse and longitudinal spread within ± 10 percent of the required rate of application

(b) When so directed by the Engineer, the Contractor shall make equipment and operators available for field testing and shall supply any other assistance required for this purpose

(c) 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 in weight shall be used in determining the spraying rate actually applied to each sheet and the variation from the mean rate for any sheet across the full width sprayed shall not exceed 15 percent

Spray bars shall be of the full circulating type Spray bar extensions shall also be of the full circulating type The spray bar shall be adjustable to maintain a constant height above the surface to be treated The spray bar nozzles shall be slotted and shall be of such design so as to provide a uniform unbroken spread of bituminous material on the surface Levers shall operate the valves so that one or all valves may be quickly opened or closed in one operation The distributor and booster tanks shall be so maintained at all times as to prevent dripping of bituminous