Pavement Surfacings

In any projects for asphalt overlay, sometimes the final product may not conform to the requirements of the specification (In this case to the Transport and Main Roads Queensland specification). 

 

So pre-determined acceptance criteria in the form of payment deduction, as provided in the relevant specification (In this case MRS30) may be applied to nonconformances for the following properties: 

 

  • particle size distribution and binder content in asphalt 

  • insitu air voids, and 

  • ride quality

 

Deductions apply to the scheduled rate for the quantity of asphalt represented by the test sample (lot or sub-lot as appropriate). 

The requirements of Clause 1.2 of MRTS30 Asphalt Pavements still apply to asphalt accepted for utilisation at a reduced level of service under this clause.

I have put some information below by referring to the MRTS30 & MRS30 which is related to the insitu air voids requirement and payment deduction criteria in case of non-conformance and I help this will be good read for quick understanding.

Technical Specification - Transport and Main Roads Specifications - MRTS30 Asphalt Pavements

1.2 Performance requirements 

The asphalt must not ravel, rut, shove, strip or bleed for the first 24 months after the Date of Practical Completion, and the surface of the asphalt must comply with the surface shape requirements specified in Table 9.6.2 for the first 12 months after the Date of Practical Completion

9.6.2 Requirement for surface shape

The surface of any trafficked layer must not pond water.

The surface shape of each course within and across traffic lanes at the time of construction must not deviate from the bottom of a straightedge laid in any direction by more than the tolerances shown in Table 9.6.2 with due allowance being made for design shape, where relevant. Where the deviations from a straightedge for an existing surface exceed 10 mm, rectification of those areas shall be carried out before the subsequent asphalt layer (other than corrector) is placed, unless directed otherwise by the Administrator.

Shape correction is typically completed using a dense graded asphalt corrector course under Work Item(s) 41751 or 41801 (as relevant), or milling (which is not covered by the Technical Specification). Further guidance about asphalt shape correction can be found in AP-PWT30 Asphalt Shape Correction.

 

All non-conformances shall be corrected before testing ride quality and before any subsequent course is placed.

9.2 Insitu air voids

 

9.2.1 Requirements for insitu air voids

 

The asphalt must have a dense appearance. Each layer of asphalt must be uniformly compacted to achieve the specified characteristic values for insitu air voids. 

Asphalt layers of ≤ 30 mm thickness shall not be tested for insitu air voids.

 

The characteristic values of insitu air voids for the lot must comply with Table 9.2.1(a) for dense graded asphalt, and with Table 9.2.1(b) for stone mastic asphalt. 

Joints are not usually tested unless the Administrator suspects the specified requirements have not been achieved. Where this occurs, the Administrator may order tests to confirm compliance.

 

For dense graded asphalt and stone mastic asphalt, insitu air voids below the minimum value may lead to rutting, flushing, bleeding and/or mix instability. Factors that influence the performance of the asphalt include traffic loading, depth of the layer from the pavement surface and the binder used in the asphalt mix.

Insitu air voids above the maximum value may lead to accelerated hardening of the binder (through oxidation), ravelling, ingress of moisture and/or stripping of the asphalt layer.

Pavement joints are typically accepted as areas with insitu air voids below the minimum value for the mat, as is represented by the lower compaction standard specified. However, under some circumstances the Administrator may consider testing of joint compaction by the Contractor where there are concerns that these reduced compaction standards may not have been achieved, for example:

• Process concerns brought about by visual or other surveillance indications, or

• Process verification at the commencement of the works, or where construction methods substantially change.

Typically joint compaction would be tested across joints where both adjoining sections of asphalt have been placed under the same contract, or within 150 mm of joints where the asphalt being tested is adjacent to asphalt not placed under the same contract.

 

Specification (Measurement) Transport and Main Roads Specifications MRS30 Asphalt Pavements

3.3 Insitu air voids

Deductions in accordance with Table 3.3 will be applied to nonconformances in excess of the upper limit of the characteristic value of insitu air voids (VU), provided the nonconformance does not exceed the limit specified in Table 9.2.1 of MRTS30 by more than 2.0%.

 

Some Note:

  • Undertake a proof rolling test of the underlying pavement (to confirm its strength) prior to placing asphalt. This requirement will be included in the next update of MRTS30. 

 

  • Use an AC10M/AC14M mix for fiddly areas such as areas which are subject to light traffic). These mixes will be easier to compact and achieve the insitu air voids requirements. AC10H/AC14H should only be used for areas subject to heavy traffic.