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The Queensland Department of Main Roads (previously DMR, now Department of Transport and Main Roads – TMR) South Coast-Hinterland District contracted Hughes McNaughton Consultants Pty Ltd to project manage the refurbishment of a section of an existing rural 2-lane unsealed gravel main road. This trial project for the refurbishment of the existing pavement incorporated the use of a soil-cement stabilising product called Renolith.
The subject road is the Wonglepong Road at Canungra in the Gold Coast Hinterland. The 750-meter section of road used in the trial was constructed of four different road pavement materials and suffered from high levels of pavement degradation and surface rutting. Most of this section of road is subject to flood inundations from Canungra Creek at irregular intervals and this results in the requirement for more regular reconstruction maintenance and trimming of the running surface.
The local municipal authority in the area, Beaudesert Shire Council (now part of Scenic Rim Region) was nominated by the DMR as the primary contractor for the construction works and provided all labour, safety personnel and signage, grader, vibrating steel drum and pneumatic tyred rollers and 7650 litre water truck. Stabilised Pavements of Australia Pty Ltd, specialist stabilising subcontractor, based in Somersby NSW, was sub-contracted to provide a CMI RS-650 reclaimer/stabiliser and spreader equipment together with a 24-tonne capacity rigid body cement spreader and an 18,000-litre water truck.
This first 650-metre section of Wonglepong Road from the Mundoolin Connection Road to the Canungra Creek bridge crossing consisted of three (3) distinctly different road pavement materials. A fourth different pavement material condition exists on the western approach to the bridge. The entire road surface suffered from severe rutting, corrugations, and local failures.
The first 300 metres from Mundoolin Connection Road was predominantly a sandy lateritic pavement with limited grade along a stunted she-oak ridge. The remainder of this section of the road to the Canungra Creek bridge consisted of approximately 150 metres of orange highly plastic sandy clay soil pavement with high fines content where the road graded vertically down to the black soil flood plain. The next 100 metre section on the western side of the bridge rose immediately out of the flood plain up a slight hill and appeared to be a well-graded orange/brown sandy clay soil with gravel pavement.
The pavement was stabilised with Renolith-cement treatment, utilising the existing road materials to a depth of 200 mm. No additional road base gravel was used. From a previous assessment of the plasticity of the clay content of the various existing road material types, it was estimated that an average of 4% cement stabilisation of the pavement materials would be required.
The trial was conducted using a mechanical reclaimer/stabiliser. The system for mixing the cement was the same as for normal cement stabilisation. For this trial, the Renolith was sprayed by means of a spray bar attachment from the back of a water truck onto the cement-mixed pavement material. This was then mixed by the reclaimer/stabiliser unit prior to a final mix with the reclaimer/stabiliser linked directly to the 18,000-litre water truck. The compaction of the pavement was undertaken by a vibrating steel drum and pneumatic rubber-tyre rollers.
The reconstruction of the 750 meters length of Wonglepong Road, 6.0 meters wide was completed in 1½ days.
The Trial Report noted that:
The sandy soils when stabilised with cement and Renolith produced a very hard running surface that did not furrow nor pothole after the 28-day trial period. The orange sandy clay soils have produced an extremely hard, and dense pavement with a glassy wearing surface following trimming. No deterioration of the pavement, surface crazing or cracking is evident, such as exists on similar road surfaces which have not been stabilized. The sandy clay soil/gravel pavement section west of the bridge has performed extremely well. There are no signs of pavement fatigue, shrinkage cracking, rutting or potholing which is evident in the adjacent untreated section of pavement.
The Renolith product when mixed with cement and stabilised appears to be a most efficient and cost-effective product for the upgrading of soil pavement roads, and especially those where a continuous construction output can be achieved. The rate of construction is dependent on only the availability of materials at the site, e.g., cement, Renolith and water, and the capabilities of the plant and expertise of the operators of that plant assigned to undertake the roadworks required.
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