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Renolith Stands Out in Pinnarendi

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Pavement Investigation

A pavement investigation was carried out on the subject section (Segment 905, near Pinnarendi) of the New England Highway. Six (6) test pits were excavated in the existing pavement. Dynamic Cone Penetration (DCP) testing was carried out in all test pits where suitable subgrade materials were encountered.

Laboratory testing was carried out on the materials encountered below the existing pavement. Three samples of the fill material below the existing pavement gravels were tested for California Bearing Ratio (CBR). Ten samples from the pavement were tested for plasticity and grading, which included mainly the base and subbase gravels.

Problem

Although the stabilised base material was relatively dry and generally non-plastic, the thickness of the layer is considered to be too thin and would not pass Circly analysis for traffic loading. The subbase material was moist in the field and again could be considered not thick enough. Subgrade material was wet and based on in-situ DCP testing, possibly indicating poor quality material of low CBR value.

Field Trial

After the pavement investigation, a 700m section of the pavement was selected to trial various stabilisation additives (123.71km to 124.41km North of Muswellbrook). The pavement within this length was split into four sections based on the incorporated additive. Section 2 (350m-550m) used 1.5L Renolith per m2 + 3% Cement.

The additives were to be mixed into the existing pavement gravels during construction to a depth of 250mm. Construction samples of the existing pavement were taken between depths of 20mm to 270mm at 100m intervals along the trial section. These samples were tested for Maximum Dry Density (MDD), California Bearing Ratio (CBR) and Plastic Index (PI).

Results

The Pinarendi Pavement Investigation and Field Trial Report made the following comments with respect to the laboratory test results from the field trial:

  • The addition of the additives resulted in an increase of CBR values by as much as 60% for 2% hydrated lime (CBR 70 to CBR 130); 150% for 1.5L Renolith per m2 + 3% Cement (CBR 50 to CBR 200); and 100% for 1.5% Polyroad (CBR 50 to CBR 150).
  • The addition of the additives resulted in a reduction in the plastic index values from PI 1 to non-plastic (PI 0) for 2% hydrated lime; from PI 8 to non-plastic (PI 0) for 1.5L Renolith per m2 + 3% Cement; and from PI 6 to PI 4 for 1.5% Polyroad.
  • The testing indicated relatively high Unconfined Compressive Strength (UCS) gains for material treated with the 2% hydrated lime (approx. 3MPa) and the 1.5L Renolith per m2 + 3% Cement (approx. 4MPa) additives. The UCS strength for material treated with 1.5% Polyroad was approximately 1.2MPa.
  • All samples exhibited capillary rise values of 100%.
  • The deflection results for Section 1 (2% Hydrated Lime) were only marginally reduced when compared to Section 4 (untreated). The deflections for Section 2 (1.5L Renolith per m2 + 3% Cement) were significantly lower and uniform, and the deflections in Section 3 (1.5% Polyroad) were actually higher than the untreated section.
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