Base-course Cbr 80 (1) 251q2r

RECONSTRUCTION OF LABIDCO CORRIDOR ROAD AND PIPEWAY

SERIES 300: ROAD WORKS SECTION 303: GRANULAR BASE COURSE 303.1

Description

303.2

Materials

303.3

Execution

3034

Protection and Maintenance

303.5

Measurement and Payment

303.1

DESCRIPTION The work to be performed under this Section shall consist of furnishing, placing and compacting crushed rock, stone or gravel to form a pavement base.

303.2

MATERIALS Crushed stone for base shall consist of one or the other of the following material: a)

Durable crushed rock consisting of angular fragments obtained by breaking and crushing solid or shattered natural rock.

b)

Durable crushed gravel stone obtained by mechanically crushing gravel boulders or stones with a minimum diameter before crushing of 200 mm.

The material shall be free of geological defects such as decomposition of strata of shale and the graded aggregate shall be free from contamination by overburden, clay, mica vegetable matter or other objectionable material. Crushed stone shall have a maximum percentage of wear of 40 as determined by the Los Angeles Abrasion Test (AASHTO T 96) as follows: The grading requirements for the aggregate shall conform to either of the following as determined using AASHTO T-27 and AASHTO T-11 and samples of the material taken from pavement layer after the compaction shall conform to the table 304.1 overleaf: Sieve Designation Standard Alternate mm No. 50 2’’ 37.5 1/1/2’’ 25.4 1’’ 19.0 ¾’ 12.7 ½’’ 4.75 No.4 2.36 No.8 0.60 No.30 0.075 No.200

Percent ing Grading A B 100 90-100 100 60-80 50-85 50-70 30-50 25-45 20-45 12-30 10-25 5-10 2-9

Table 304.1 Requirements for Granular Base Course S303 - 1

RECONSTRUCTION OF LABIDCO CORRIDOR ROAD AND PIPEWAY

To minimize the effects that compaction induced crushing of soft materials may have on the quality of the materials used, samples for the grading shall be taken after compaction. In addition to conforming to the grading requirements, the material shall not be gap-graded, nor shall the curve of distribution of those particles sized smaller than D60 deviate by more than +3% on any specified sieve from lying parallel with the grading envelope, where D60 is the sieve size through which 60% by weight of the material es. The coarse aggregate, that is, aggregate retained on a No. 4 (4.75 mm) sieve, should have a percentage wear of not more than 40% as determined by test method AASHTO T96 (ASTM C 131). The material should be capable of giving a Soaked California Bearing Ratio value of at least 80% when tested in accordance with AASHTO T193 (ASTM D 1883) at 100% of the maximum dry unit weight and at the optimum moisture content as determined by test method AASHTO T180 (ASTM D 1557) (Modified Proctor). For all gradings, that portion ing a No. 40 (0.425 mm) Sieve, should be non-plastic or should have a liquid limit of not more than 25 and a plasticity index of not more than 6 when tested in accordance with AASHTO T89, T90 (ASTM D 4318). After crushing, the material should be angular in shape with a Flakiness Index of not more than 35% as determined by BS 812: Part 105. At least 50% by numerical count of all coarse aggregate particles retained on the No. 4 (4.75 mm) sieve should have at least one fractured face or should be naturally angular with sharp edges. The Aggregate Base Course should be placed and compacted in layers not exceeding 150 mm compacted thicknesses. Each lift of aggregate base course material should be compacted to at least 100% of the maximum dry unit weight as determined by test method AASHTO T180 (ASTM D 1557).

303.3

EXECUTION Base material shall be placed on sub-base only after the sub-base has been inspected by the Engineer, immediately prior to the proposed start of base laying execution and it is found to be in conformance with the specification. The sub-base shall be maintained in acceptable condition while base is being placed. Deformations, ruts, etc., caused by haulage vehicles or other plant and equipment shall be restored at Contractor's expense. The Contractor shall take care to load and haul the material to the Works so that it arrives in a un segregated condition and stock pile maintained for Engineer to sample & approve material. The material after approval from the Engineer at designated stock pile shall be mixed water at -2% or + 4% at laboratory determined OMC, hauled in trucks and spread by self-spreading vehicles or towed spreader boxes and no layer shall exceed 150mm compacted thickness. A grader must not be used to spread the material. The material shall be deposited on the sub-base at a uniform quantity per linear metre, which quantity will provide the required compacted layer thickness without resorting to spotting, picking-up or otherwise shifting the aggregates to whole required width of carriage way. When the required compacted thickness is more than 150 mm, the material shall be spread and compacted in two or more layers of approximately equal thickness. Each layer shall be spread and compacted in a similar manner and be approved prior to the placement of a succeeding layer. The surface of each layer shall be maintained in acceptable condition at all times. Deformation ruts, etc., caused by hauling vehicles and other equipment or plant shall be restored at Contractor's expense. S303 - 2