Use of recycled crushed concrete for road pavement sub-base

This paper presents a case study on the use of recycled crushed concrete by VicRoads as a fully bound pavement sub-base for deep strength asphalt pavements. VicRoads standard specification Section 820 for unbound crushed concrete pavement sub-base and Section 821 for cement treated crushed concrete (CTCC) sub-base (Class CC3) is discussed together with laboratory and field evaluation of the performance as an alternative to Class 3 cement treated crushed rock (CTCR) sub-base. The paper also discusses some of the limitations of the dynamic test methods for acceptance of construction but promotes their use to rank non-standard materials against materials with an established history of performance. Since January 1993, approximately 520,000 tonnes of crushed concrete has been placed in road pavements in Melbourne of which approximately 200,000 tonnes has been placed as CTCC sub-base (Class CC3) for deep strength asphalt pavements constructed on the Western King Road. Results of limited testing for resilient modulus carried out in the laboratory using the MATerials Testing Apparatus (MATTA), and the Repeated Load Triaxial Test Apparatus (RLTTA) are presented, including the results of field testing using the ARRB Falling Weight Deflectometer with back-calculation of modulus values using the ARRB developed computer program EFROMD2. From dynamic testing carried out to date it appears that the performance of Class CC3 crushed concrete is at least as good as Class 3 crushed rock either in a bound or unbound pavement sub-base.