Expanding The Definition Of Source Rock

Source Rock for the Production of Crushed Rock and Aggregates

EXPANDING the definition of source rock to include recycled rock is the latest change to be proposed by VicRoads.The VicRoads Construction Materials group is responsible for the development and enforcement of standards and codes of practice for construction materials used on VicRoad’s jobs.

Two key documents are Section 801 – “Source Rock for the Production of Crushed Rock and Aggregates” and RC500.00 – “Code of Practice for Source Rock Investigations “. Both of these documents have been re-drafted as part of this activity.

Section 801 covers the durability, hardness and, where applicable, the polished stone value requirements of source rock used for the production of crushed rock and aggregates for engineering use.

The requirements for pyroclastic rocks (scoria) are covered in Section 818 and for recycled crushed concrete in Section 820. The requirements for gravel, sand and soft or ripped rock are covered in Section 811.

The key change in Section 801 has been the inclusion of the term ‘recycled rock’ in the definition of source rock. The definition of ‘recycled rock’ is given as:

Rock obtained from a location other than a quarry, within a construction site. Recycled rock is usually processed by an on-site portable plant but may also be taken to a nearby quarry for processing.

The use of recycled rock from an accredited source is permitted in the specification for the production of “sub-base crushed rock”. The advice of the Director – Technical Consulting or delegate should be sought before approval of the source is given. The use of recycled rock for the production of base (Class 1 and 2) crushed rock will not be normally permitted, however, it may be considered for works with a Design Traffic Loading of less than 1 x 106 Equivalent Standard Axles at the discretion of the Superintendent.

The Code of Practice provides additional guidance in relation to ‘recycled rock’ with particular reference being made to newer basalt surface rocks typically to the west of Melbourne. In this case,VicRoads may classify such sites as accredited sources of ‘Newer Basalt Surface Rock’. Technical Consulting maintains a set of reference jars titled‘Newer Basalt Surface Spalls’.

Standard source rock tests are carried out on recycled rock, that is testing of durability (i.e. degradation factor,secondary mineral content, accelerated soundness content, texas ball mill), sulphur mineralisation, hardness (LA value) and resistance to polishing(Polished Stone Value).

Another change that has occurred is the ability to use pebbles in structural
concrete.

Until recently, the use of pebbles in structural concrete has not been permitted, however on the basis of local and overseas data presented to VicRoads, the use of pebbles in concrete mix designs may be allowed in structural concrete up to 50MPaunder certain conditions. Reference should be made to Standard Section 610 which contains some additional durability requirements pertaining to the use of pebbles sources relating to LA Value, Wet & Dry Strength and Sodium Sulphate Soundness over and above the Section 801 requirements.

The CMPA has been asked to make comment on these draft documents which has been prepared by Sarah Andrew. At this stage a formal position has not been reached with comments due mid-May.

If you would like copies of the drafts or the CMPA’s submission, call the office or check out the submission area of the CMPA website.

Copies of these standards and other documents released by VicRoads can be sourced online. Simply go to www.vicroads.vic.gov.au. Follow the link to “Publications & Forms”, “VicRoads Online Bookshop” and then “Roads and Pavements”.

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