Key parameters controlling dynamic modulus of crushed reclaimed asphalt paving–powdered rock–Portland cement blends

In order to minimise the impact on the environment of reclaimed asphalt paving (RAP) disposal, a policy was established in Brazil determining that such residue should be recycled and used in roadways whenever possible. Mixing RAP with powdered rock and Portland cement to be used as a base/sub-base of pavements has been experienced with interesting results. Though, there is a lack of studies on the mechanical properties (unconfined compressive – qu and split tensile – qt) and the viscoelastic behaviour (dynamic modulus – E* and phase angle – δ) of RAP – powdered rock – Portland cement blends. The present research aims at quantifying the influence of amounts of Portland cement (C) and the effect of the porosity (η) of the compacted blend in improving qu, qt and E* of the mixtures. This paper advances in the understanding of the key parameters controlling strength and stiffness of compacted RAP – powdered rock – Portland cement mixtures by quantifying the influence of porosity/cement index (η/Civ) on qu and qt strengths and mainly on the viscoelastic behaviour (E* and δ), including the effect of frequency (F) and the testing temperatures (TT). A single qt/qu relationship equal to 0.17 was found, being independent of the η/Civ. On the other side, it is shown that η/Civ is an appropriate parameter to assess both the E* and the qu of the RAP – powdered rock – Portland cement mixtures studied. The phase angle (δ) of the compacted mix is not affected by η/Civ, being slightly influenced by F and TT. It varies from a minimum of 3° at low testing temperatures and high frequency to a maximum of 14°.