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Section 821

VicRoads

 

        SECTION 821 - CEMENTITIOUS TREATED CRUSHED CONCRETE FOR PAVEMENT SUBBASE

 

##This section cross-references Sections 175, 801 and 820.

If any of the above sections are relevant, they should be included in the specification.

If any of the above sections are not included in the specification, all references to those sections should be struck out, ensuring that the remaining text is still coherent:

 

    821.01 DESCRIPTION

This section covers the requirements of 20 mm nominal size crushed recycled concrete or crushed rock/concrete blends for pavement subbase, treated with cementitious binder to produce bound material. 

 

    821.02 DEFINITIONS

 

Cementitious Binder

A cementitious material capable of being uniformly mixed into a granular pavement material to bind the particles to increase strength.  Cementitious binders include Portland cement Type GP or blended cement Type GB, or a blend of ground granulated iron blast furnace slag (GGBFS), hydrated lime, fly ash, alkali activated slag or other pozzolanic material supplied in accordance with this specification. 

Cement Treated Crushed Concrete

Cement treated crushed concrete is a mixture of crushed concrete fragments, cement, water, or crushed rock with approved additives, meeting foreign materials limits, and produced at a controlled mixing plant to close tolerances of grading, moisture content and binder content. 

Fly Ash

A fine powder of pozzolanic material extracted from the flue emissions produced from the burning of black coal complying with the requirements of the current Australian Standard for Supplementary cementitious materials for use with General purpose and blended cement - Fly ash as listed in Section 175. 

Pozzolan

A siliceous or alumino-siliceous material when finely ground that can be mixed with lime or portland cement to form a cementitious material. 

Slag (Ground Granulated Iron Blast Furnace Slag)

Ground Granulated Iron Blast Furnace Slag (GGBFS) complying with the requirements of the current Australian Standard for Supplementary cementitious materials for use with General purpose and blended cement – GGBFS as listed in Section 175 is a pozzolan produced by fine grinding of slag produced as a by product from the smelting of iron ore. 

 

    821.03 COMPONENTS

 

The crushed concrete component used in the manufacture of cement treated crushed concrete shall comply with the requirements of Section 820.

 

    (a) Coarse Aggregates

      Coarse crushed concrete aggregates shall consist of clean, hard, durable, angular rock, concrete and sand fragments of uniform quality complying with durability and soundness requirements specified in Clause 821.04.

 

© VicRoads  May 2013

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    (b) Fine Aggregates

      Fine aggregates shall consist of clean, hard, durable, angular rock, concrete and sand fragments of uniform quality.

    HP If all or part of the fine aggregates is to be imported from a different source or manufactured from a different rock type to that of the coarse aggregates, the Contractor shall obtain approval of the Superintendent prior to use.  The Contractor shall provide details of the exact location of the source and nature of the fine aggregates and the proposed percentage by mass to be added to the crushed concrete mixture.

      If approved, all imported fine aggregates produced from igneous and metamorphic rock sources shall have a Degradation Factor - Fine Aggregate of not less than 60.

 

    (c) Additives

      Additives which are non durable or subject to appreciable breakdown will not be permitted.  The addition of crushed brick or Reclaimed Asphalt Pavement (RAP) is not permitted in cement treated crushed concrete.

      VicRoads will only approve the addition of an additive as a part of a registered crushed rock mix design submitted in accordance with VicRoads Code of Practice for Registration of Crushed Rock Mix Designs as listed in Section 175.

 

    (d) Blending of Crushed Concrete Aggregates with Crushed Rock Aggregates

    HP Crushed rock aggregates imported from different sources or rock types shall not be combined with crushed concrete aggregates without prior approval from the Superintendent.

      Any proposal to blend aggregates from different sources or rock types shall clearly state the proportions by mass retained on each sieve for each rock type that will be used in the blend.

      Blending of crushed rock with crushed concrete may be permitted subject to the following conditions being met:

       (i) All coarse crushed rock aggregates other than crushed concrete aggregates, in the blend shall individually comply with the relevant requirements of Section 801 for a crushed rock subbase of the relevant rock type.  The crushed rock to be added shall meet the unsound rock requirements of Table 821.031.

       (ii) All material to be blended shall be fully crushed and screened to the maximum aggregate size permitted in the product prior to blending.

       (iii) All crushed rock fine aggregates added to the blend shall comply with the requirements of Clause 821.03(b).

       (iv) Once a suitable blend has been developed, the total proportions by mass of crushed rock and crushed concrete in the blend shall not be varied by more than 5% by mass.

       (v) Prior to addition of cement, the crushed concrete/crushed rock blend shall comply with the requirements specified in Clause 821.04.

          Table 821.031 Unsound Rock Requirements of Crushed Rock Coarse Aggregates
Total of Marginal and Unsound Rock

%  (max)

Unsound Rock

%  (max)

20 10
 
 

© VicRoads  May 2013

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    821.04 PRODUCT

 

Cement treated crushed concrete mixes for use on specified works can be registered in accordance with VicRoads Code of Practice for Registration of Crushed Rock Mix Designs as listed in Section 175.

 

    (a) The crushed concrete prior to the addition of cementitious binder shall comply with the requirements of Table 821.041.

 

      Table 821.041  Atterberg and Hardness Limits Test Properties
Test Test Value
Liquid Limit % (max) 35
Plasticity Index (max) 10
Los Angeles Value (max) 40
 
 

    (b) Any component or product which may contain asbestos must be managed and tested in accordance with the requirements of WorkSafe Victoria including the current Occupational Health and Safety (Asbestos) Regulations.

 

    (c) Foreign materials in that fraction of the product retained on a 4.75 mm sieve shall not exceed the percentages by mass specified in Table 821.042.

 

      Table 821.042  Foreign Material
Foreign Material Type % Retained
High density materials such as metal, glass, brick, asphalt, stone, ceramics and slag 3
Low density materials such as plastic, rubber, plaster, clay lumps and other friable material 1
Wood and other vegetable or decomposable matter 0.2

 

    821.05 CEMENTITIOUS BINDER

 

    (a) Cement

      Portland and blended cement shall be Type GP (rapid setting binder) or GB (medium setting binder) and comply with the requirements of the current Australian Standard for General purpose and blended cement as listed in Section 175.  It shall be stored in weatherproof structures, and any cement damaged by moisture shall not be used.

      If Type GB cement is proposed, only the following blends are permitted:

            (i) Cement/Slag blend (50% to 60% cement content)

            (ii) Cement/Fly ash blend (70% to 80% cement content)

            (iii) Cement/Slag/Fly ash blend (55% to 65% cement content)

 

© VicRoads  May 2013

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    (b) Slag/Lime Blend

      Slag and hydrated lime may be used in blended combination to produce a slow setting cementitious binder.  Slag used shall be Ground Granulated Iron Blast Furnace Slag (GGBFS) meeting the requirements of the Australian Standard for Supplementary cementitious materials for use with General purpose and blended cement – Slag (GGBFS) as listed in Section 175.  The Contractor shall nominate the type, brand and source of the GGBFS to be used.  Hydrated lime shall meet the requirements of the current Australian Standard for Limes and limestones – Limes for building as listed in Section 175.

      Slag/lime shall be blended uniformly in the ratio of 85% slag to 15% hydrated lime unless laboratory testing indicates that superior strength of the cementitious treated material is achieved by using a different ratio.  If the blend is to be varied, the proportion of lime shall not be less than 10%.  The Contractor shall provide evidence that the blend ratio has been met for all material supplied to the job.

      Slag/lime blend shall have a mortar bar 7 day compressive strength of 10 MPa and 28 day compressive strength of 16 MPa.  The test shall be the same test specified for portland and blended cements except that the cement to water ratio shall be adjusted to match the consistency of mortar produced for the compressive strength test for GB cement in accordance with the relevant Australian Standard Test Method.

 

    (c) Slow Cementitious Blends Incorporating Alkali-activated Slag or Fly Ash

      Special blends of slow setting cementitious stabilising agents incorporating alkali-activated slag or fly ash which do not meet mortar bar strength requirements specified in the Australian Standard for Supplementary cementitious materials for use with General purpose and blended cement – Fly ash as listed in Section 175 may be used subject to the blend satisfying the mortar bar test requirement specified in Clause 821.05(b).  The maximum binder working time shall be determined in accordance with the VicRoads Test Method for Determination of the Maximum Allowable Working Time for a Cementitious Binder as listed in Section 175 to confirm that the binder is a slow setting binder.

      Fly ash shall be supplied to meet the requirements of the Australian Standard for Supplementary cementitious materials for use with portland and blended cement – Fly ash as listed in Section 175.

 

    821.06 WATER

 

Water added to the crushed concrete shall be clean and substantially free from detrimental impurities such as oils, salts, acids, alkalis and vegetable substances.  Water sources shall be tested prior to use for electrical conductivity and pH, in accordance with the current Australian Standards as listed in Section 175.  The electrical conductivity shall not be more than 3500 µS/cm and pH within the range of 6 to 10.  Water sources classified by the relevant water authority as potable water shall be exempt from this requirement.  Water sources shall be tested at a maximum of 12 monthly intervals or when in the opinion of the Superintendent the nature of the water source has changed.  The use of reclaimed water will require the approval of the Superintendent and shall conform to VicRoads guidelines for recycled water for road activities as listed under other referenced documents in Section 175.

 

    821.07 GRADING OF CRUSHED CONCRETE WITHOUT CEMENTITIOUS BINDER

 

After completion of production, but before compaction, crushed concrete shall comply with the relevant grading requirements of Table 821.071 corresponding to the nominal size of the material.

 

The crushed concrete or blended material shall not be graded from near the coarse limit on one sieve the fine limit on the following sieve or vice versa.

 

© VicRoads  May 2013

Section 821 (Page 4 of 7)

 

 

Initially the target grading shall be at the centre of the grading envelope but the target grading may be varied within the specified grading limits to optimise the cementitious binder content required to satisfy the Unconfined Compressive Strength (UCS) requirements specified in Table 821.081.  Regardless of the target grading, the production grading shall not extend outside the specified grading limits.

 

Table 821.071  Grading Requirements
Sieve Size

AS (mm)

Limits of Grading

Test Value before Compaction

(% Passing)

26.5 100
19.0 95 – 100
13.2 75 – 95
9.5 60 – 90
4.75 42 – 76
2.36 28 – 60
0.425 10 – 28
0.075 2 – 10

 

    821.08 CEMENTITIOUS BINDER CONTENT AND UNCONFINED COMPRESSIVE STRENGTH (UCS) REQUIREMENTS

 

    (a) Cementitious Binder Content

      The Contractor shall determine the content of cementitious binder required to meet the minimum 7 day UCS specified in Table 821.081 using modified compaction.  The cementitious binder content may be further increased to allow for the effects of production variability.  The resulting Design Cementitious Binder Content shall not be less than the minimum cementitious binder content specified in Table 821.081.

      Cementitious binder shall be added and mixed into the crushed concrete to produce a uniform binder content.

      After mixing, the cementitious binder content of the mixture, expressed as a percentage by mass of the dry crushed concrete, shall be within 0.3% of the Design Cementitious Binder Content.

 

    (b) Unconfined Compressive Strength Test

      The Contractor shall carry out UCS testing in accordance with the test frequency specified in Table 821.121.  The UCS test result shall be the mean UCS determined from a pair of specimens in accordance with the current Australian Standard for Unconfined compressive strength of compacted materials as listed in Section 175 and compacted using modified compactive effort.

      One representative sample of fully mixed cementitious treated material shall be taken either from the plant or at the point of delivery in accordance with the current Australian Standard for Unconfined compressive strength of compacted materials as listed in Section 175 and compacted in the mould within two hours of mixing.

 

© VicRoads  May 2013

Section 821 (Page 5 of 7)

 

 

      Assessment of the UCS during production shall be on a ��rolling average�� basis where the average of the most recent three UCS test results shall not be less than the minimum value specified in Table 821.081.

        Table 821.081 Cementitious Binder Content and Unconfined Compressive Strength
    Pavement Design Modulus (MPa) Minimum Design Cementitious Binder Content (% by mass) Minimum 7 day Mean UCS (MPa)
    Rapid Setting

    (GP Cement)

    Medium Setting

    (GB Cement)

    Slow Setting

    (Supplementary Cementitious Blends)

    �� 500 3 4 # #
    > 500  or  �� 3500 3 5 3.5 3

 

    821.09 MOISTURE CONTENT

If the contract is only for supply and delivery of material to VicRoads, the moisture content of the mixture at the point of delivery, expressed as a percentage by mass, shall be within plus 0.5 to minus 1.0 of any target value nominated by the Superintendent.

 

    821.10 STOCKPILING OF MIXTURE

Where cementitious treated crushed concrete is stockpiled, prior to loading, the batching time shall be recorded on the delivery docket.

 

    821.11 HANDLING OF MIXED MATERIAL

Handling of mixed crushed concrete, including discharging from the mixing plant and the loading of trucks, shall minimise segregation.

 

    821.12 MINIMUM TESTING REQUIREMENTS

 

The Contractor shall test the cementitious treated crushed concrete at such a frequency to ensure that all material consistently complies with the specified requirements.

 

The test frequency shall initially not be less than that shown in Table 821.121, except that the frequency may be at half the specified frequency for Grading, Foreign Material Content, Plasticity Index, USC, Degradation Factor – Fine Aggregate, and Los Angeles Value if a minimum of ten of the most recent test results in succession have met specification requirements. If any subsequent test result fails, another test shall be immediately completed.  If the second test fails, the test frequency shall revert to the minimum frequency specified in Table 821.121 and the Contractor shall not return to half the test frequency until a further ten successive test results comply.

 

© VicRoads  May 2013

Section 821 (Page 6 of 7)

 

 

Table 821.121  Minimum Frequency of Testing
Test Minimum Frequency of Testing
Grading On each production day:  one per 500 tonnes except where the total production on any day is less than 100 tonnes.
Foreign Material Content On each production day:  one per 500 tonnes except where the total production on any day is less than 100 tonnes.
Cementitious Binder Content On each production day:  one per 250 tonnes except where the total production on any day is less than 100 tonnes.
Moisture Content On each production day:  one per 500 tonnes except where the total production on any day is less than 100 tonnes.
Plasticity Index In each month:  one per 5000 tonnes.
Degradation Factor - Fine Aggregate One per production day for crusher fines imported from another source or location within the source to that of the course aggregates.
Los Angeles Value One per month or at any time when in the opinion of the Superintendent, the nature of the material has changed.
Mean Unconfined Compressive Strength In each week:  one per 2000 tonnes.  If production in any week is less than 500 tonnes, the quantity may be added to subsequent production until a total of 500 tonnes is reached.
 

© VicRoads  May 2013

Section 821 (Page 7 of 7)

 


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