The purpose of this method statement is to describe steps for flexible pavement that can also include asphalt driveway rehabilitation and road resurfacing.
The sequence of the work to be carried out shall be as follows:
- Resurfacing Works
- Partial Reconstruction Works
- Total Reconstruction Works
- Cold In-Place Recycle (CIPR) – Cement Treated Base
- Cold In-Place Recycling (CIPR) – Foamed Bitumen
- Hot In-Place Recycling (HIPR)
Below is list of different type of machinery that is required for the flexible pavement works.
i. Back pusher with power broom
ii. Diamond Cutter and jack hammer
iii. Milling Machine
iv. Water tanker
v. Air compressor
vi. Bituminous Tack Coat distributor
vii. Tipper lorries
viii. Asphalt paver
ix. Tandem roller & Pneumatic Tyre roller
x. Recycler
xi. Bitumen Tanker
xii. Motor Grader
xiii. Pre-heater
xiv. Re-mixer
General Project Site Requirements
Before starting full-scale work, a trial lay is required to ensure that the asphalt mixture will be produced according to the design mix specification and familiar with the actual operations on site.
An electronic sensor paver shall be used for laying of asphalt pavement. Laying temperature shall be in the range of 125o C and 170o C.
Compaction shall be carried out using the specified equivalent type of rollers and compacted in accordance with the specification.
Rolling shall be commenced from the lower to the higher side. The final rolling temperature shall not less than 110o C.
The surface of asphalt pavement shall be finished to the grade and line as required and a joint survey shall be carried out to confirm these.
Coring shall be carried out to determine the compaction 24 hours after laying.
Driveway Asphalt Resurfacing Method
Demarcation on site shall be carried out to determine the extend of repair area.
Joint survey on existing pavement shall be carried out prior to the commencement of milling works.
Milling out of the existing to a depth of not exceeding 110mm or as shown in the accompanying drawings.
The surface to receive the premix shall be cleaned, free from dirt, loose materials and standing water.
Supply and apply bituminous Tack Coat prior to the laying of ACBC. The spray rate of the Tack Coat shall be between 0.15 to 0.30 liters/sq.m.
The approved premix shall be delivered to site by tipper trucks. To prevent loss of heat, the mixture shall be covered by tarpaulin.
Supply, lay and compact ACBC as specified thickness including necessary regulating works. Materials and workmanship shall be as per specification. The ACWC shall be laid the next day after completion of ACBC.
Supply and apply bituminous tack coat prior to the laying of ACWC.
Supply, lay and compact ACWC as specified thickness including the necessary regulating works. Materials and workmanship shall be as per specification.
Asphalt concrete shall not be opened to traffic until compaction has been completed and the materials has thoroughly cooled and
set in the opinion of the Engineer’s representative. This is usually not less than 4 hours from the initial of rolling.
Method of Partial Road Reconstruction Works
Demarcation on site shall be carried out to determine the extend of repair area.
Joint survey on existing pavement shall be carried out prior to the commencement of milling and excavation works.
Milling and excavate out of the existing asphalt and road-base layers to a required depth or as shown in the accompanying drawings.
In the event of inclement weather a “drainage channel” cut through the shoulder to prevent water ponding on the milled/excavated
surface.
Preparing the existing unbound base course for the application of the DBM. This preparation consists of
(a) proof rolling to identify weak areas in the unbound base,
(b) repairing the unbound base in weak areas using crushed stone,
(c) further rolling to meet density requirements.
The surface to receive the premix shall be cleaned, free from dirt, loose materials and standing water.
Supply and laying of prime coat/tack coat on the prepared unbound base, and allowance for a curing period.
Supply, lay and compact DBM layer with a nominal maximum stone size of 40 mm to required thickness.
Supply and apply bituminous Tack Coat prior to the laying of ACBC. The spray rate of the Tack Coat shall be between 0.15 to 0.30 liters/sq.m.
The approved premix shall be delivered to site by tipper trucks. To prevent loss of heat, the mixture shall be covered by tarpaulin.
Supply, lay and compact ACBC as specified thickness including necessary regulating works. Materials and workmanship shall be as
per specification. The ACWC shall be laid the next day after completion of ACBC.
Supply and apply bituminous tack coat prior to the laying of ACWC.
Supply, lay and compact ACWC as specified thickness including the necessary regulating works. Materials and workmanship shall
be as per specification.
Asphaltic concrete shall not be opened to traffic until compaction has been completed and the materials has thoroughly cooled and
set in the opinion of the Engineer’s representative. This is usually not less than 4 hours from the initial of rolling.
Method of Driveway Pavement Total Reconstruction Works
Demarcation on site shall be carried out to determine the extend of repair areas.
Joint survey on existing pavement shall be carried out prior to the commencement of milling and excavation works.
Milling and excavate out of the existing asphalt, road-base and unsuitable sub-grade layers to a required depth or as shown in the
accompanying drawings.
All formation and Sub-base/upper-base preparation shall be followed specification.
In the event of inclement weather a “drainage channel” cut through the shoulder to prevent water ponding on the milled/excavated
surface.
The surface to receive the premix shall be cleaned, free from dirt, loose materials and standing water.
Supply and laying of prime coat/tack coat on the prepared unbound base, and allowance for a curing period.
Supply, lay and compact DBM layer with a nominal maximum stone size of 40 mm to required thickness.
Supply and apply bituminous Tack Coat prior to the laying of ACBC. The spray rate of the Tack Coat shall be between 0.15 to 0.30 liters/sq.m.
The approved premix shall be delivered to site by tipper trucks. To prevent loss of heat, the mixture shall be covered by tarpaulin.
Supply, lay and compact ACBC as specified thickness including necessary regulating works. Materials and workmanship shall be as per specification. The ACWC shall be laid the next day after completion of ACBC.
Supply and apply bituminous tack coat prior to the laying of ACWC.
Supply, lay and compact ACWC as specified thickness including the necessary regulating works. Materials and workmanship shall be as per specification.
Asphaltic concrete shall not be opened to traffic until compaction has been completed and the materials has thoroughly cooled and set in the opinion of the Engineer’s representative. This is usually not less than 4 hours from the initial of rolling.
COLD IN-PLACE RECYCLING (CIPR) – CEMENT TREATED BASE
This Work shall include the breaking, mixing compacting and shaping the cement stabilized base course in accordance with this specification and the lines, levels, grades, dimensions and cross-sections shown on the drawings and/or as required by the Engineer.
Setting up the Recycling Train
Recycling should only commence once all preliminary requirements have been met. These include, in order of sequence:
A thorough check on all machines and equipment to be used in the recycling operation, including rollers and water tanker.
The bags of cement based on calculation, shall be placed at regular internal along stretch of works.
Check that the recycling operator has all the data concerning the rate of application of stabilizing agents for keying into the computer, that there is a clear guideline for the full length of cut and that all start-up procedures are clearly understood.
Preparatory Works
Prior to the commencement of works, the areas should be thoroughly investigated and checked. Presence of any underground utilities especially cabling work shall be detected and marked in order to avoid damaged during the mixing operation. Any utilities that could not be avoided during the stabilization operation, relocation works need to be done.
Coring and Investigation
Coring need to be done to identify the thickness of the existing pavement.
Upon identify the thickness of each of the pavement layer, the thickness of the asphalt and the existing crusher run base in the vicinity of the determined recycle stabilization areas should be taken for sieve analysis and laboratory compaction. The dosage of stabilizing agent such as Ordinary Portland Cement (OPC) to be applied in respect to the required strength shall be pre-determined in the Laboratory by Unconfined Compression Strength Test.
Pre-Treatment
If the base is wet and above the Optimum moisture content, the base material need to be pre-treated. The process of pre-treatment using the stabilizer machine or any other mechanical mean approved by the Engineer is by pulverized the base material to dry-out the material until below the Optimum moisture Content before the process of spreading the cement for stabilization.
Spreading of Stabilization Agent
The determined recycle stabilization areas shall be marked and the required quantity of cement shall be spread over the areas. If case of the stabilization area is small, spreading could be done manually, in order to reduce the spreading cost. To have a uniform spreading, the cement bags shall be placed in areas that already been marked off, opened and spread with a rake or other mechanical mean alike.
The Ordinary Portland Cement (OPC) or any other stabilizing agent in powder form shall be spread with the mechanical spreader in order to get a better production of the works.
The quantity of the cement for recycle stabilization area shall be spread manually to the required design.
The rotor of stabilizer shall be so adjusted that the required thickness of breaking and mixing is achieved after compaction. The area near edge of the pavement shall be worked by shifting the rotor of the stabilizer sideways, the maximum offset outward from machine wheel is 35cm on either side.
Breakdown Compaction
When necessary to have a break-down compaction after mixing, pneumatic tired roller shall be used for break-down compaction.
Sprinkling of water from pneumatic tired roller shall be permitted to obtain the Optimum Moisture Content (OMC) during the break-down compaction.
Vibrating roller with 20 t static mass ideal is use with rolling pattern of 2 passes static and 6 passes vibration. Moisture content is the most critical variable in achieving densification with minimum effort. Due to the time delay between recycling and finishing off, a light application of water should always be applied to the surface before final rolling.
Trimming and Compaction
Immediately after break-down compaction (if require), undulations shall be eliminated by a motor grader. Further compaction by a pneumatic tired roller or a vibratory roller shall be used for full pavement compaction.
To achieve best suitable compaction the moisture content of the mixture should be controlled to an about of Optimum Moisture Content (OMC). Fine trimming by motor grader to obtain the required level after final compaction.
Final smooth rolling by pneumatic tired roller to knead down any loose material left over on the surface.
Prime Coating
After compaction of the above operations, prime coat of cationic Bituminous Emulsion with Bitumen content not less than 58% shall be sprayed at the rate 0.5L/m2 – 1.0L/m2.
Trial Area
Prior to the commencement of site works, it is recommended a trial area shall be carried out to establish the rolling method, required to produce the specified field density. The established method thereafter shall be used be used as a standard for site control.
COLD IN-PLACE RECYCLING (CIPR) – FOAM BITUMEN
This Work shall include the breaking, mixing compacting and shaping the foamed bitumen stabilized in accordance with this specification and the lines, levels, grades, dimensions and cross-sections shown on the drawings and/or as required by the Engineer.
Setting up the Recycling Train
Recycling should only commence once all preliminary requirements have been met. These include, in order of sequence:
- A thorough check on all machines and equipment to be used in the recycling operation, including rollers and water tanker.
- The bags of cement based on calculation, shall be placed at regular internal along stretch of works.
- Check that the recycling operator has all the data concerning the rate of application of stabilizing agents for keying into the computer, that there is a clear guideline for the full length of cut and that all start-up procedures are clearly understood.
Preparatory Works
Prior to the commencement of works, the areas should be thoroughly investigated and checked. Presence of any underground utilities especially cabling work shall be detected and marked in order to avoid damaged during the mixing operation. Any utilities that could not be avoided during the stabilization operation, relocation works need to be done.
Coring and Investigation
Coring need to be done to identify the thickness of the existing pavement.
Upon identify the thickness of each of the pavement layer, the thickness of the asphalt and the existing crusher run base in the vicinity of the determined recycle stabilization areas should be taken for sieve analysis and laboratory compaction.
The dosage of stabilizing agent such as Ordinary Portland Cement (OPC) and foamed bitumen to be applied in respect to the required strength shall be pre-determined in the Laboratory by Indirect Tensile Test.
Pre-Treatment
If the base is wet and above the Optimum moisture content, the base material need to be pre-treated. The process of pre-treatment using the stabilizer machine or any other mechanical mean approved by the Engineer is by pulverized the base material to dry-out the material until below the Optimum moisture Content before the process of spreading the cement for stabilization.
Spreading of Stabilization Agent
The determined recycle stabilization areas shall be marked and the required quantity of cement shall be spread over the areas. If case of the stabilization area is small, spreading could be done manually, in order to reduce the spreading cost.
To have a uniform spreading, the cement bags shall be placed in areas that already been marked off, opened and spread with a rake or other mechanical mean alike.
The Ordinary Portland Cement (OPC) or any other stabilizing agent in powder form shall be spread with the mechanical spreader in order to get a better production of the works.
The quantity of the cement for recycle stabilization area shall be spread manually to the required design. The binder properties for foamed asphalt material shall be bitumen grade 80/100 penetration and temperature during foaming is between 160oC – 180oC.
The bitumen tanker shall consist of heating system capable to raise the temperature of the bitumen by at least 20oC per hour.
The actual bitumen and water content to produce foam asphalt shall be determined at laboratory prior mixing in-situ will be carried out.
The rotor of stabilizer shall be so adjusted that the required thickness of breaking and mixing is achieved after compaction. The area near edge of the pavement shall be worked by shifting the rotor of the stabilizer sideways, the maximum offset outward from machine wheel is 35cm on either side.
HOT IN-PLACE RECYCLING (HIPR)
HIPR or Hot In-Place Recycling is a method of road rehabilitation where existing pavement is recycle and laid back in one single pass.
The process is most suitable to rehabilitate pavement experiencing functional distress i.e. surface cracking, minor rutting and shoving etc.
HIPR Process and Construction Method
The existing pavement is heated between 90oC – 100oC to soften the bituminous surface layer. Clusters of infrared heaters fed with propane gas which radiate thermal energy onto the wearing course surface shall do the pre-heating process.
Additional heater banks on the Remixer heat the asphalt wearing course to the working temperature of about 120oC – 140oC.
The surface temperature can be effectively controlled via the variable gas pressure, heater bank height and forward speed.
The rotating scarifier fitted with spirally shaped carbide-tipped scarify the surface to the required depth.
New virgin material and rejuvenator will be added into the pug-mill where thorough mixing is done. The amount of this two materials is controlled electronically and shall be followed the approved mix design.
The final remixed materials is discharge from the pug-mill in the windrow and evenly spread over the heated surface with a vibrating and temping screed.
The Remix asphalt shall not be opened to traffic until compaction has been completed and the materials has thoroughly cooled and set in the opinion of the Engineer’s representative. This is usually not less than 4 hours from the initial of rolling.
Trial Area
Prior to the commencement of site works, it is recommended a trial area shall be carried out to establish the rolling method, required to produce the specified field density. The established method thereafter shall be used be used as a standard for site control.
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