Technical Clarification

Gabions as a non-concrete application

Technical Clarification Number


For the additional 3rd point of credit Mat-5 as it relates to “non-concrete applications (e.g. stone sub-soil drains, road layerworks and backfill, etc.)”,​ the GBCSA confirm that gabions can be excluded as they are deemed to not be aggregates for the purposes of this credit.



Technical Clarification

Definition of non-structural in-situ concrete

Erratum Number


Under MAT 5, to achieve the additional 3rd point:

 1) 10% of all aggregate used for structural (concrete) purposes is to be recycled aggregate (equivalent to Class 1 RCA as per Australian standard HB155-2002) or slag aggregate; AND

2) No virgin aggregates are used in non-structural in-situ concrete applications (e.g. (concrete) footpaths, (concrete) curbs, (concrete) backfilling to service tranches, etc.) and non-concrete applications (e.g. stone sub-soil drains, road layerworks and backfill, etc.)

 The definition of non-structural in-situ concrete is, according to GBCSA, ‘not forming part of any load bearing or engineered element that is poured on site’. And similarly the definition of structural concrete, according to the GBCSA, is ‘forming part of any load bearing or engineered element’. A structural engineer can determine on a project how this definition applies to specific applications.


Technical Clarification

Portland cement content in concrete reference cases

Technical Clarification Number


A concrete reference case is typically provided in Mat-5 Concrete credit submissions to demonstrate the percentage of total Portland cement replaced in all concrete uses by supplementary cementitious materials (SCM).

To ensure consistency in Green Star project submissions and the assessments of this credit, the GBCSA deems it acceptable for project teams to present concrete reference cases that assume the use of baseline concrete mixes with 100% Portland cement content (i.e. use no SCM).

Projects may still provide concrete reference cases with more realistic mix designs that do contain some percentage of SCM, which is common industry practice, however this is not mandatory.


Credit Interpretation Request

Approval of published mix design ratios

Credit Interpretation Request Number


It is left up to the Concrete Technologist’s professional discretion to put forward a reference case that has the same structural and functional requirements, and apply to the same location and season.

Should the Concrete Technologist believe that the mix design ratios published by the Cement and Concrete Institute (CNCI) or any other reputable source/authority is an acceptable reference to calculate the reference case mix design for their specific project, this will be deemed acceptable. It is neither the GBCSA’s nor Assessors’ prerogative to question this.

The determined reference case must be stated in the Concrete Technologist report as per the documentation requirements stipulated in the Green Star SA Retail v1 Technical Manual.


Technical Clarification

Short Report meets the requirements for both these two Documents- the Short Report and Concrete Mixed Report requirement

Technical Clarification Number


The project team is to ensure that the concrete mixed report is included in the short report and meets all credit criteria as laid out in the Green Star SA Technical Manual. Please clearly highlight where the Concrete mixed report is to be located in the short report.



Technical Clarification

Concrete mix design for each concrete application in both the concrete mix report and in the tender documentation

Technical Clarification Number


The project team in the extracts from contract documentation need not detail the full mix composition or proportions provided that the contract documents clearly require the cement replacement or virgin aggregate reduction as required by the credit criteria. The mix composition or proportions must however be shown in the concrete mix report.




Virgin aggregate in pre-cast non-structural items.

Erratum Number


On page 268 of the Green Star SA – PEB v1 Technical Manual, under ‘Credit Criteria’, additional point, change the last bullet point to read “No virgin aggregates are used in non-structural concrete uses (e.g. footpaths, backfilling to service trenches). Note that this requirement applies to non-structural concrete aggregate applied on site and not to pre-cast non-structural concrete uses.”




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