VICROADS – THE NEW SECTION 831
DR ELIZABETH GIBSON, General Manager for CMPA reports on the new Section 831.
THE following is a summary of the response to CMPA from VicRoads received 12 July 2013 regarding issues with new Section 831.
CMPA requested for a minimum ALD of 3.2 to be allowed for 7mm Class B sealing aggregate rather than the current minimum requirement of ALD ≥3,5.
VicRoads introduced a minimum ALD requirement of 3.5 for 7mm in July 2012, in response to a number of significant issues being experienced with 7mm spray seals which had resulted in rework at substantial additional cost.
VicRoads responded that at this stage VicRoads prefers to maintain a minimum ALD of 3.5 for all 7mm products until robust performance data is available to re-assess the impact of reducing the minimum ALD requirement. However, further consideration to the proposed change will be given in 12 months time.
Issues with NATA requirements in regards to reporting to the nearest 0.1%
VicRoads understands that some NATA assessors have raised concern with the “measurement uncertainty” relating to reporting to the nearest 0.1%. VicRoads state that there is a vast difference between 0.6 5% and 1.4% passing 0.075 sieve on the potential performance of sealing aggregates.
VicRoads has specified this requirement to ensure the fine dust components of the aggregate product has no more than 1.0% passing 0.075 sieve. Whilst VicRoads is able to join in the discussion with NATA to facilitate an outcome which achieves the needs of all parties; VicRoads believes that the issue is one for NATA and the industry should take a lead role on. CMPA will explore this issue with NATA.
Measurement of ALD on 7mm aggregate.
Whilst VicRoads does not require the Flakiness index (FI) on 7mm aggregate to be reported, an ALD measurement is required to substantiate that the aggregate product has an ALD ≥3.5. At this stage, VicRoads will accept the measurement of ALD’s by using either the “traditional nomograph” or “mousetrap” methods depending on the preference of the supplier.
VicRoads will continue to monitor this aspect during the forthcoming “spray sealing” season to ensure the ongoing use of both methods of ALD measurement is appropriate.
Measurement of Plasticity Index (PI)
Vic Roads has given some consideration to adopting the “wet preparation” method rather than the current specified “dry preparation”. This is due to some concerns that PI’s for crushed rock products are often being underestimated. With respect to the use of the “one point method” for determination of the Liquid Limit (LL), rather than the “four point method” currently specified;
VicRoads view is that the one point method may have some applicability for use where the PI of the crushed rock is < 2. However, for crushed products with PI ≥2 the four point method is seen as the most accurate way of assessing the LL and ultimately the PI of the material. Another alternative could be to discuss the use of “cone penetrometer” for the measurement of the LL of crushed rock products. This issue will be discussed at the next VicRoads CMPA meeting.
Joint meeting between CMPA and CCAA to discuss sealing aggregate issues.
VicRoads will arrange a meeting between CMPA, CCAA and VicRoads to discuss common issues to be held at the end of August 2013.
Stacksite Location and Condition
VicRoads greatly appreciated the attendance and the quality presentations made by Mark Wagner of Conundrum Holdings and Craig James of E.B Mawson and Sons on behalf of CMPA. The meeting was held on 28 May 2013 with the Bituminous Surfacing group and a summary of the presentation is given in this issue of Sand & Stone.
Permeability Requirements for Crushed Rock Products
In the issue (14/11/12) of draft changes to Standard Section 812, permeability requirements have been revised to address some of the issues being experienced by suppliers of Class 3 CR. As a part of the promulgation of these changes, VicRoads Technical Services will engage as far as practical with specification writers to ensure that permeability values are only included where necessary in VicRoads contracts and that consistency of specification requirements is apparent.
In terms of the surveillance of quarry products, VicRoads will ensure that permeability reports are only required as part of a registered mix design application or alternatively when the supplier company is manufacturing crushed rock products for VicRoads funded works.
The next meeting between CMPA and VicRoads Technical Services will take place in September/October 2013.
If members have any other issues that they would like to raise at the meeting or would like a copy of the VicRoads letter, please contact Elizabeth Gibson, General Manager for CMPA on elizabeth.gibson@cmpavic.asn.au
You must be logged in to post a comment Login