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Introduction

Polyroad is a dry powdered polymer (DPP) used as a stabilising binder for rehabilitation of granular pavements or new pavement construction. Polyroad effectively waterproofs granular materials that would otherwise lose significant strength during moisture ingress.

The stabilising powder within Polyroad consists of a polymer thermally bound to an “inert fine carrier”, which is then mixed with hydrated lime. The lime is not coated with polymer. The function of the lime is to flocculate and prepare clay particles for adhesion to the polymer. The carrier, which is encapsulated by the polymer, is effectively inert and does not  react chemically in the stabilisation process. The function of the carrier is to facilitate uniform distribution of the polymer throughout the granular material.

Construction Procedure

Pavement construction with Polyroad is carried out using the same plant and equipment that is used for pavements incorporating cementitous binders.

As typically desired in any form of in situ pavement stabilisation process,at least two mixing runs are recommended to ensure optimum results. It is also recommended the polymer stabilised pavement be compacted at 1 to 2% dry of optimum moisture content (OMC). Unlike cementitous stabilised materials, there is no time restriction associated with Polyroad in achieving specified compaction.

Additionally, Polyroad stabilised materials can be re mixed, reshaped or re-compacted without loss of dry strength. Typical spread rates of Polyroad are 1.5 % to 2% by mass. Two (2) Polyroad products are available depending on material properties.

Testing For Suitability

To determine the suitability of Polyroad for stabilisation, tests such as plasticity index, grading, maximum dry density and optimum moisture content should be undertaken.

Additional testing that clearly highlights Polyroad’s superior performance can be seen from the waterproofing effect when tested in accordance with AS 1141.53 – Absorption, Swell and Capillary Rise (compare with untreated sample and if desired, with a sample treated with lime only).

Testing can also be carried out to assess CBR strengths – comparative testing with and without Polyroad, both soaked and unsoaked (compare with untreated sample and if desired, with a sample prepared with lime only).

Design Considerations

Pavement thickness can be determined in exactly the same manner as for unbound flexible pavements. However, a history of successful performance in the field has shown that reduced pavement thickness has continued to provide maintenance free service.