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METHOD STATEMENT
COLD IN-PLACE RECYCLING – CEMENT TREATED
1.0 OBJECTIVE The purpose of this method statement is to describe the activities and methods, which will be used to carry out FLEXIBLE PAVEMENT (Rehabilitation and Resurfacing).
2.0 CONSTRUCTION METHOD The sequence of the work to be carried out shall be as follows:2.1 General Requirements 2.2 Resurfacing Works 2.3 Cold In-Place Recycle (CIPR) – Cement Treated Base
2.1 General Requirements 2.1.1 Before starting full-scale work, a trial lay is required to ensure that the asphaltic mixture will be produced according to the design mix specification and familiar with the actual operations on site. 2.1.2 An electronic sensor paver shall be used for laying of asphaltic pavement. Laying temperature shall be in the range of 125 o C and 170o C. 2.1.3 Compaction shall be carried out using the specified equivalent type of rollers and compacted in accordance with the specification. 2.1.4 Rolling shall be commenced from the lower to the higher side. The final rolling temperature shall not less than 110 o C. 2.1.5 The surface of of asphaltic pavement shall be finished to the grade and line as required and a joint survey shall be carried out to confirm these. 2.1.6 Coring shall be carried out to determine the compaction, 24 hours after laying. 2.2 RESURFACING WORKS 2.2.1 Demarcation on site shall be carried out to determine the the extend of repair area.
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METHOD STATEMENT
COLD IN-PLACE RECYCLING – CEMENT TREATED 2.2.2 Joint survey on existing pavement shall be carried out prior to the commencement of milling works. 2.2.3 Milling out of the existing to a depth of not exceeding 110mm or as shown in the accompanying drawings. 2.2.4 The surface to receive the premix shall be cleaned, free from dirt, loose materials and standing water. 2.2.5 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. 2.2.6 The approved premix shall be delivered to site by tipper trucks. To prevent loss of heat, the mixture shall be covered by tarpaulin. 2.2.7 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. 2.2.8 Supply and apply bituminous tack coat prior to the laying of ACWC. 2.2.9 Supply, lay and compact ACWC ACWC as specified specified thickness including the necessary regulating works. Materials and workmanship shall be as per specification. 2.2.10 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. 2.3 COLD IN-PLACE RECYCLING (CIPR) - CEMENT TREATED TREATED BASE 2.3.1 Description 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.
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METHOD STATEMENT
COLD IN-PLACE RECYCLING – CEMENT TREATED 2.3.2 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.
2.3.3 Preparatory 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. 2.3.4 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 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. 2.3.5 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. 2.3.6 Spreading of Stabilization Agent
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METHOD STATEMENT
COLD IN-PLACE RECYCLING – CEMENT TREATED The determined recycle stabilization areas shall be marked and the required quantity of cement shall be spread 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 required for recycle stabilization area shall be computed using the following formula:C
=
Ar x Tr x δc x Rc 100
Where C C Ar Tr δc
Rc
= = = = =
Quantity of cement needed (kg) Area for recycle stabilization (cm2) Thickness of recycle stabilization (cm) Density of the unconfined samples (kg/cm3) at the required cement % Required cement %
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. 2.3.7 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.
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METHOD STATEMENT
COLD IN-PLACE RECYCLING – CEMENT TREATED 2.3.8 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 viabratory 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. 2.3.9 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/m 2 – 1.0L/m 2. 2.3.10 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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METHOD STATEMENT
COLD IN-PLACE RECYCLING – CEMENT TREATED
3.0 PLANT AND EQUIPMENT Type of machineries required, i. ii. iii. iv. v. vi. vii. viii. ix. x.
Back pusher with power broom Diamond Cutter and jack hammer Milling Machine Water tanker Air compressor Bituminous Bituminou s Tack Coat distributor Tipper lorries Asphalt paver Tandem roller & Pneumatic tyre roller Recycler
