Holbrook Concrete Overlay Performance Assessment

Authored by Peter Carson, Director, Carson Group Pty Ltd
Endorsed by Tim Buckinghan-Jones, James Walker and Brendan Leader

Carson Group funded by the Australian Society for Concrete Pavements through its Innovation Fund provide an independent review of the technical aspects of the performance of a 4km Continuously Reinforced Concrete Pavement (CRCP) overlay of the Hume Highway Northbound carriageway located approximately 15-19km north of the township of Holbrook. The overlay was constructed in 1991. This report provides a brief history of design and construction, reviews 33 years of performance, provides a snapshot of condition at this point in time and makes some recommendations. The concrete overlay has performed well over the past 33 years with 2.5% of the slow lane replaced in a single event, and 0.8% of the fast lane replaced over its life, for a total of 1.6% replacement of the CRCP overlay in 33 years. It is notable that an early life repair was undertaken at the southern anchor which was likely due to construction practise and this repair accounts for 100% of the repairs in the fast lane and 50% of overall repair area. If this area was removed from the assessment a total of 0.8% of slab replacement would have been undertaken on the entire overlay. This compares favourably with a similar aged section of CRCP on the M1 Motorway (1993) southbound which had 8.1% patching in the slow lane and 3.4% total patching. Comparisons are also made to the Newcastle Inner City Bypass at Jesmond to Callaghan (1994) and Newcastle Link Road (1993) which have had performed better and with much lower, and almost no maintenance intervention.

The overlay has retained its surface shape and texture which contrasts with adjacent flexible pavements that currently show significant rutting.

A commentary and analysis is made on factors that have contributed to the success of this low maintenance pavement including the consistently good quality roughness results that have sustained over the life of the pavement without any intervening diamond grinding.

The Holbrook overlay was constructed with a widened 4.6m slow lane slab with integral shoulder. This width exceeds the current standard and a change to reduce this width on any future overlay would likely result in a more durable pavement.

The cost to construct a concrete overlay versus an asphalt pavement is similar and dependent on market forces. However, the maintenance cost of a CRCP overlay is considerably cheaper than an equivalent asphalt pavement according to RTA’s Report on SH2 - Hume Highway, the Relative Pavement Costs Between Mittagong and Goulbourn21.