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SECURITY AND SAFENESS VRAMP – CONTRACT PACKAGE RAP/CP15 – MAINTENANCE OF NH6 FROM KM193÷KM233 IN SON LA AGGREGATE SUBBASE, BASE COURSES TABLE OF CONTENTS I REFERENCE STANDARDS II MATERIAL III EQUIPMEN[.]

AGGREGATE SUBBASE, BASE COURSES

TABLE OF CONTENTS

I REFERENCE STANDARDS

II MATERIAL

III EQUIPMENT AND CHECKING

IV CONSTRUCTION OF AGGREGATE BASE AND SUBBASE LAYERS

I REFERENCE STANDARDS

All the material was tested and approved by Engineer before using The Contractor shall submit to the Engineer to know about the source of material and the Engineer will approve these sources before the material is delivery to site Where the material does not meet the requirements of Technical Standards, the Contractor shall provide materials from other sources The transportation of materials from the processing stage will be accompanied by the manufacturer's certificate and report of testing to indicate that material in accordance with the requirements of the specification

The following Standards in their latest edition shall be particularly applied to the works covered by this Specification Section:

TCVN 8859:2011 Graded Aggregate Base and Subbade Pavement –Specification for Construction and Acceptance 22TCN 332-06 Testing procedures on definition of CBR value for soiland macadam in laboratory 22TCN 333-06 Procedures of soil and macadam compaction in laboratory 22TCN 318-04 Aggregate Abrasion- Los Angeles Method

TCVN 7572-06 Aggregates for Concrete and Motar- Determination ofBulk Density and Vois in Aggregate

II MATERIAL

1 Aggregate subbase

Aggregate for subbase shall consist of hard particles crushed from crude rocks with minimum compressive strength of 40 MPa to the size and of the quality requirements

of this Specification section The material shall be- clean, free from vegetable matter, lumps or balls of clay, or deleterious substances, and shall be of such nature that it can

be compacted readily to form a firm and stable subbase

The subbase material gradation shall conform to Table 2 The Contractor shall nominate the adopted gradation for each source in their submittal under Clause 4 of this Specification section This gradation shall apply for all material from this source

If materials from different sources are delivered to site, they shall be stockpiled and placed in separate layers and/or lots

Table 1 : Grading Requirement for Aggregate Subbase

Standard (mm)

Mass Percent Passing

Dmax= 37.5mm Dmax= 25mm

-Standard (mm)

Mass Percent Passing

Dmax= 37.5mm Dmax= 25mm

Table 2 : Aggregate Subbase Properties

1 Abrasion of Aggregate 40% max TCVN 7572-12:2006

2 Plasticity index of aggregate passing the0.425mm 6 max TCVN 4197:1995

3 PP Index = Plasticity Index Ip x % materialpassing portion 0.075mm ≤ 60

4 Percent by weight of aggregate retained on

2.36mm (No.8) sieve with at least one fractured face

50% min

5 Liquid Limit of aggregate passing the0.425mm 35% max TCVN 4197:1995

7

Content (%) of flat rhombus gain (Testing grain with diameter 4.75mm and accounting for > 5% of sample weight)

≤ 20%

2 Aggregate base

Aggregate for base shall consist of hard particles crushed from crude rocks with minimum compressive strength of 40 MPa to the required size and quality specified in this Specification section The material shall be clean, free from vegetable matter, lumps or balls of clay, or other deleterious substances, and shall be of such nature that

it can be compacted readily to form a firm and stable base

The base material shall conform to the grading requirements The Contractor shall nominate the adopted gradation for each source in then submittal under Clause 4 of this Specification section This gradation shall apply for all material from this source (c) If materials from different sources are delivered to site, they shall be stockpiled and placed in separate layers and/or lots

Table 1 : Grading Requirement for Aggregate Base

Standard (mm)

Mass Percent Passing

Dmax= 25mm Dmax= 19mm

Table 2 : Aggregate Subbase Properties

1 Abrasion of Aggregate 35% max TCVN 7572-12:2006

No Properties Subbase Test Method

2 CBR at 98% of MDD soaked 96h ≥100

2 Plasticity index of aggregate passing the0.425mm 4 max TCVN 4197:1995

3 PP Index = Plasticity Index Ip x % materialpassing portion 0.075mm ≤ 45

4 Percent by weight of aggregate retained on

2.36mm (No.8) sieve with at least one fractured face

50% min

5 Liquid Limit of aggregate passing the0.425mm 15% max TCVN 4197:1995

7

Content (%) of flat rhombus gain (Testing grain with diameter 4.75mm and accounting for > 5% of sample weight)

≤ 18%

III EQUIPMENT AND CHECKING

The Contractor shall arrange the construction equipment with good quality for the implementation of project

All kinds of construction equipment have been tested and registered for its activities And they are mobilized for the project was approved by the Engineer.Use of equipment with the best performance, ensure high productivity, good quality, low cost, and reducing of the hard work for employees

Technology chain must focus on synchronous and the balance between plant productivity and manual labor It must be based on characteristics of the Works and construction technology, Schedule, scope of work and other requirement in the Projects

Regular and timely improvement of construction equipment and manual labor in order

to ensure consistency, balance and facilitate the application of advanced construction technology

Constantly improve the management level, technical level and take the repair construction equipment, well observed periodic maintenance and repair for equipments

Equipping with proper facilities for the technical maintenance and repair of construction equipment, corresponding to equipped capacity

Construction equipment and material shall be managed and organized and stable in the construction group as well as highly specialized

The management and use of materials, equipment (including use, maintenance and moving) must comply with the specification of manufacture and competent authorities for the driver, operator …Assign the driver, driver and operator to match with trained professionals and workers of skills

The vehicles, construction machines were put into operation, ensuring the technical reliability and safeness For these vehicles, construction machines must be registered for safety, before being put into execution, must fulfill the registration test under the provisions of the competent authorities of the State of Vietnam

The technical maintenance must be done by the competent group To organize a team

of professional maintenance and repair techniques for each type of construction equipment and machines

IV CONSTRUCTION OF AGGREGATE BASE AND SUBBASE LAYERS

1 Preparation of road form.

After the completion of road base, the preparation the road mold in according to the specification, including repair of defects on the top of road base K98, in the detail as follows:

- Repair the all defects on the road, to clean the surface, to wet the surface

- Setting up the road mold before commencement of work The contractor will carry out the repair the road mold to ensure its accuracy, sufficient dimension in shape To construct the fish bone ditch both sides of road with distance of 10 -15m, to set up 01 water drainage trench

2 Equipment and Manpower

Equipment and method used shall place the Aggregate Subbase and Aggregate Base

to the line, levels, grades, dimensions and cross-section shown in the Drawings and as directed by the Engineer A self-contained, sensor system, power propelled paving machine approved by the Engineer shall be used to place the aggregate base course The Engineer has the right to stop the use of any equipment or plant which he deems

to be inferior to the qualify required and to instruct the removal of such equipment and to have it replaced by suitable equipment or to alter the method of operation at any time

The Contractor shall immediately comply with such instructions without being entitled to any indemnities or extensions as a result of such instructions The Contractor shall not be allowed to use any equipment or plant before obtaining the approval of the Engineer, and the Contractor shall undertake to follow sound technical methods in operation and to engage skilled and trained operators, mechanics and labor

to carry out the Works The Engineer has the right to expel any operators, mechanics

or labor and to insừuct suitable replacement thereof at any time he deems such action

is necessary

3 Trial section

Before either subbase or base construction is started, the Contractor shall spread and compact trial sections and submit the result for approval as directed by the Engineer The purpose of the dial section is to check the suitability of the materials and the efficiency of the equipment and construction method which is proposed to be used by the Contractor Therefore, the Contractor must use the same materials, equipment and procedures that he proposes to use for the main work One trial section of a lane’s width by 150 meters in length shall be made for every type of material and/or construction equipment/procedure proposed for use

The Engineer will dhect the number of density tests and other tests required to be carried out

If the materials in the Engineer’s opinion are not suitable for subbase or base, the material shall be removed at the Contractor’s expense, and a new trial section shall be constructed

If the basic conditions regarding the type of material or procedure change during the executionof the work, new trial sections shall be constructed

4 Execution of base and aggregate subbase foundation

4.1 Placing

Before placement, the material shall be gathered on site (storage yard) The moisture shall be in the range of ±2% of the optimal moisture during the process of transportation and rolling In case of low moisture, additional watering is applied with raining cock With high moisture, the material shall be spread for aừ drying before rolling

The aggregate subbase and base material shall be placed in accordance with Drawings

as a uniform mixture in a quantity which will provide the required compacted thickness In locations where subbase or base materials are to be placed on a prepared subgrade, the subgrade shall be prepared in accordance with Specification, prior to base and/or subbase placement

When placing subbase and base material over existing asphalt pavement, the existing pavement shall be prepared by fun-owing in accordance with Specification

When more than one layer is required, each layer shall be compacted as specified in the Specification section, and evidenced as conforming, before the succeeding layer is placed

The area being prepared for laying the subbase and base material shall be completed and the approval of the Engineer obtained for at least 200m ahead of the placing of

Hauling equipment may be routed over completed portions of the subbase and base courses provided no damage results and provided that such equipment is routed over the full width of the course tỏ avoid rutting or uneven compaction The Engineer has the right to stop all hauling over completed or partially completed subbase and base courses when in his opinion such hauling is causing damage

4.2 Spreading

Where the required thickness is 150mm or less, the material may be spread and compacted in one layer Where the required thickness is more than 150mm, the aggregate subbase and base shall be spread and compacted into two or more layers of approximately equal thickness, and the maximum compacted thickness of any one layer shall not exceed 150mm unless otherwise directed by the Engineer All subsequent layers shall be spread and compacted in a similar manner

During the construction, to guarantee the density at the shoulder edge, the Aggregate shall be spread at least 20cm wider than the edge Without spreading, the aggregate shall be filled in framework to guarantee the uniform rolling density for the entire width of aggregate layer as designed

Aggregate Subbase and Aggregate Base shall be delivered to the roadbed as a uniform mix and shall be spread at a moisture content within the range specified in this Specification section The moisture shall be uniformly distributed throughout the material

Aggregate Subbase and Aggregate Base shall be spread and shaped in a manner which does not cause segregation of the fine and coarse aggregate particles Segregated material shall be corrected or removed and replaced with graded material Immediately following final spreading and smoothing, each layer shall be compacted

to the full width by means of approved compaction equipment Rolling operations shall begin along the edges and progress gradually towards the center, in a longitudinal direction On superelevated sections rolling shall begin at the low side and progress towards the high side The rolling operation shall continue until all roller marks are eliminated and the layer is uniformly compacted and the aggregates firmly keyed Any irregularities or depressions that develop shall be corrected by loosening the material at these places and adding or removing material until the surface is smooth and uniform Along curbs, headers and walls, and at all places not accessible

to the roller, the subbase and base material shall be compacted thoroughly with approved tampers or compactors At the end of each shift, the surface of the base and subbase shall be shaped and sloped to prevent ponding of rainwater

Aggregate Base surfaces which are to receive a prime coat shall then be further compacted to produce a stable, tightly locked surface, without open pores, suitable for priming All coarse aggregate shall be tightly locked in place Under no circumstances shall any form of soil or fine aggregate be added to the surface to assist the locking process, which shall be achieved by compaction only Vibration shall not be used in the final stages of the compaction of the surface The Engineer may direct that

pneumatic rollers be used for the final surface Compaction, if static steel wheeled rollers are considered likely to cause excessive breakdown or degradation of the aggregate base

In case of not processing the layers above the finished graded aggregate, watering is requừeđ for maintenance and environment protection

4.3 Compaction

Compaction shall be carried out only when the moisture content of the material is within the range of 3% less than optimum moisture content to 2% more than optimum moisture content, where the optimum moisture content is as defined by the maximum modified dry density determined by standard of 22 TCN 333-06

When the underlying material is soft or yielding, compaction shall be stopped and the underlying materials rectified as directed by the Engineer

During all the operations of spreading, compacting and leveling of subbase and base course material, care must be taken so that layers already compacted under the layer being executed are not affected, or that the finished subgrade or base surface is also not affected Special attention must be given in places where equipment makes turns

in going back and forth Any such damage resulting in mixing the various layers constituting the different subgrades and base courses shall be carefully made good by the Contractor at his expense and to the

If the layer of subbase or base material, or part thereof, does not conform to the required finish, the Contractor shall, at his own expense, make the necessary corrections

Compaction of each layer shall continue until a field density of at least 100 percent of the maximum dry density determined in accordance with 22 TCN 333-06 In place density determination shall be made in accordance with 22 TCN 346-06

Rolling sequence:

Rolling by Preliminary rollers 1012T with 34 times / points with V = 1.5 : -2km/h

- Use vibration roller when reaches 16-25T rolling 12 -18 times / points with V= 2.5 -:- 3 km/h

- Rolling for completion by steel roller 10-12T, with 3-4 times / points with V= 3km/ h

- Number of times be determined be needed rolling through the test results to achieve density requirements

- It must be wet with water during the process to compensate for evaporation of water during construction and keep the surface moisture during compacting