06 7 ok CW2C BASE

Reference to the macadam material: The most recent printing of the following Vietnamese or AASHTO tests shall apply to the materials covered in this Section: The most recent editions of

BASE COURSES

TABLE OF CONTENTS

I MATERIAL REQUIREMENTS

II EQUIPMENT AND CHECKING

III CONSTRUCTION OF AGGREGATE BASE AND LEVELLING LAYERS

IV EXECUTION OF BASE COURSES

V INSPECTION AND ACCEPTANCE

CONSTRUCTION OF THE BASE AND BASE COURSES

I. Material requirements

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

Reference to the macadam material:

The most recent printing of the following Vietnamese or AASHTO tests shall apply to the materials covered in this Section:

The most recent editions of the following standards shall apply to the materials covered in this Section:

methods on grade aggregate foundation in highway pavement

compaction of road

foundation and embankment by sand cone method

in laboratory

for soil and

macadam in aboratory

Degradation of

Small-Size Coarse Aggregate by Abrasion and Impact in the

Los Angeles Machine

Magnesium

Sulphate

Relations of

Soils Using a 4.54-kg (10-lb) Rammer and

a 457-mm

(18-in.) drop

Bearing Ratio

Elongated Particles,

or Flat and Elongated Particles in Coarse Aggregate

Materials of construction must, before putting in the work, be tested to check the grain composition analysis, the best moisture if meet the technical standards and regulations approved by the Engineer will be allowed to spread

In addition, all construction materials of macadam aggregate foundation must meet the technical requirements specified in the Regulations and Specification

Materials shall be so stored and handled as to assure the preservation of their quality and fitness for construction Materials, even though approved before storage or handling, may again be inspected and tested prior to use Stored material shall be located to facilitate prompt inspection

Handling and stockpiling of aggregates shall be to the approval of the Engineer and at all times be such as to eliminate segregation of the various sizes and contamination

Aggregate stockpiles for base course and base shall be protected from rain

to prevent saturation of the aggregates which would result in a reduction in the quality of the placed material or adversely affect the placement of the material

Where separate size materials are to be blended to meet the gradation, such blending shall be as directed by the Engineer and shall be accomplished prior to delivery to the roadway

MATERIAL REQUIREMENTS

The aggregate for base course and aggregate levelling course shall consist

of hard, durable particles and shall be crushed stone, crushed slag, or crushed or suitable natural material and filler of natural or crushed sand or other finely divided mineral matter The aggregate shall be free from vegetable matter and lumps or balls of clay, and shall be of such nature that

it can be readily compacted to form a firm and stable base The materials shall comply with the requirements given in tables 1 and 2 below

Table 1 Grading Requirement for Aggregate Standard

(mm)

Mass Percent Passing

19mm

-37,5 95 - 100 100

No Properties Aggregate Test Method

T193

T89(*)

5 PP Index = Plasticity Index Ip x % material ≤ 45 ≤ 60

passing portion 0.075mm

D4791

T180 Note:

(*) Liquid Limit, Plasticity Index are specified by test with material passing sieve 0.425

mm

(**) Aggregate with diamond or flattened shapes has thickness or width less than 1/3

length or

equivalent;

Test is conducted with various sieves of diameter of more than 4.75mm and accounting for more

than 5% of sample quantity

Aggregate with diamond or flattened shapes content of taken sample is average results

certified

for each sieve

Aggregate with a Dmax = 25mm is appropriate Base Course

Aggregate with Dmax = 19mm (Aggregate Levelling Course) shall be used for levelling and strengthening existing pavement structure in the rehabilitation of roadway sections

II. Equipment and checking

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

Constructional flow line 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

Construction Equipments as follows:

+ Full set of test devices

III. Construction of Aggregate Base and Levelling layers

1 Preparation of road bed.

After the completion of subgrade, the preparation the road bed in according

to the specification, including repair of defects on the top of subgrade K98,

in the detail as follows:

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

will carry out the repair the road bed to ensure its accuracy, sufficiently 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

The Contractor spread the macadam aggregate by the Aggregate paver (Aggregate Base) in combine with the motor grader (Aggregate Base)

Spread layer is allowed a maximum of 18cm (after compacting), Aggregate paver has the vibration bar to ensure the density ≥ 90% immediately after spreading

The test equipment in the construction process:

- The Sand Equivalent Test Set (to check for dirt)

site of Contractor

Other construction equipment beside of the spreader:

pump with tap, water sprayer with portable showers watering by hand

+ Steel roller 6 - 8T

+ Vibration roller 12-35 T

+ Steel roller 10 - 12t

IV. Execution of base courses

1. Construction of Base

layers for the construction

- To facilitate the construction as well as the movement for the construction vehicles the construction will executed alternatively 1/2 the width of the Road

1.1 Trial Sections

Before either base construction is started, the Contractor shall spread and compact trial sections as directed by the Engineer The purpose of the trial 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

Equipment for the work must be mobilized to site and setting up the construction site before commencement of work The construction equipment includes of dump truck, water spraying equipment including tank truck, pump with hose, hand watering sprayer, spread machine, the compaction means including steel rollers 8-10 T, Bomag Roller, SAKAI Roller

12 - 35T and steel rollers 10-12 T

Determining the spreading coefficient:

The spreading coefficient K is determined by formula

γCmax K

K sp =

γCtn

In which :

to standard result of testing density

+ K: is defined density equal to or greater than 0.98

(according to experience Ksp = 1.28 ÷ 1.38)

Construction of macadam aggregate includes of the following steps:

ensuring that the humidity is greater than the optimum moisture content from -3% ÷ 2%

after spreading and compacting

storage area (to check the character of macadam aggregate at the storage area and approved by Engineer in writing) Using the front loader to load to the dump truck then transported to the site (macadam aggregate must be met the needed moisture to prevent the segregation in the transportation

that the outer edge also achieve the specified density

- The moisture of material is always best If it is not met the requirement, taking the adjustment by drying If the material is too dry, spray with water by shower to avoid the drifting of the small particles The Contractor shall adjust moisture in yards for materials to ensure uniformity

- In the construction process to regularly monitor surface elevation of macadam aggregate, the compensation or removing to the uneven areas shall be taken by worker, to ensure the macadam aggregate surface is always been flat, creating a compacting homogeneous mass, creating horizontal slope as designed

- In case occurrence of segregation, ripples or improper during the spreading it must be taken the repair of it

be plough with depth of 5cm before compensation of material

preliminary rolling, densely rolling and completion rolling.This process is done when the material approaches the density requirements Density

of material is certified by the methods of sand cone under the presence

of the Engineer

Rolling sequence:

- Rolling by Preliminary rollers 8-10T with 3-4 times / points with V = 1.5 -: - 2km / h

- Use vibration roller 25T pass 12 -18 times / points with V = 2.5 -: - 3 km /h

with V = 3 km / 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

Density requirements :

- K ≥ 98% of the entire layer, in the process, it is regularly checked density by sand cone method

coefficient and rolling passes on a point, then giving the proposal from the construction requirements in accordance with the process and technological lines the stages: prepare spread, compaction, quality control materials after shipment, check the availability of vehicle quality, motorcycles, to assign the proper manpower to each working assembly

- After determining the coefficient of compaction, rolling passes and approved by the Employer and Engineer, will spread on a large scale

1.2 Spreading on a large scale

work

+ Base is carried out by Contractor into layers with calculated thickness (before rolling), so as to achieve the designed thickness

-40cm each side of spread line to ensure compaction

- Setting up the rolling line after testing rolling Use a light roller (8-10T)

to do preliminary compacting base, then use steel rollers and vibrating rollers to achieve density requirements

achieve the necessary density and optimal rolling

the uneven points or ripples during the spraying if there is any segregation or has not yet reached a density requirements, material of entire such place must be replaced on new macadam aggregate, no mixing or compensation in place Check regularly to monitor the spread materials Compacting right along the edges and gradually goes to the center vertically At the location that the roller is able to access, the worker shall use the plate vibrator to compact to the required density

to higher edge Compacting shall be continued until no wheel rolling tracks on the surface layer, material meet the density and stability

+ Preliminary rolling :Stability rolling the aggregate by roller

8−10t

- The macadam aggregate after being completed must be met the requirement of shape, level, density, flat and approved by Engineer and Employer

2. Curing of the macadam aggregate layer

base layer before spraying of the bitumen and kept regularly to water

stopped 2 days before spraying of the bitumen on the surface of base.

layer is regularly watered on the surface by a watering tank truck with shower, minimize movement on this surface

process, only being stopped if execution the upper layer or the surface

of the base layer is spraying bitument (depending on the weather conditions and must be stopped few days before spraying of bitumen)

V. Inspection and Acceptance

construction process to monitor all of the materials being used on site The scope of the tests will be approved by Engineer, but at least ensure the following requirements:

- The supporting test data required for initial source approval of the material shall include all the tests specified in this Section on at least three representative samples from the proposed material source, selected to represent the range of material quality likely to be obtained from the source Where observed changes in the material or in its source or in its method of production occur the material shall be re-submitted for source approval

- All holes in the finished work made by density testing or otherwise during testing shall be backfilled by the Contractor without delay Holes shall be filled with the specified material and compacted to the density and surface tolerance requirements of this Specification Section

- During construction routine material quality control testing shall be carried out to monitor the material being brought on site The extent of the testing shall be subject to the approval of the Engineer, but shall be

at least as detailed below

 5 plasticity index tests

 5 particle grading tests

routinely determined using –AASHTO T180 The test shall be made to the full depth of the layer at locations as directed by the Engineer, but not more than 200 m apart

samples shall be taken from material at the site and tests shall be conducted for every 1000 cubic meters from each material supply source or when material quality is extraordinary Material shall meet all physical properties specified in Tables Nos 1&2 and compacting test conducted inside the Laboratory

- Moisture, aggregate material separation (visual observation and checking sieve particle) Test on moisture and sieve particles shall be conducted for every 200 m3 aggregate or every shift;

- Compacted density: tests shall be conducted on every finished aggregate layer by sand cone according to AASHTO T180 or equivalent process as required by the Engineer At the final stage of compacted density, test for checking compacted density shall be frequently performed and taking as basis for completion of compact works, test for compactness shall be conducted for every 800m2 at each random position;