Sustainable 'Green' Overlays for Strengthening and Rehabilitation of Concrete Pavements.

A cost effective, minimal disruption, sustainable and environmentally friendly alternative to the wholesale demolition, removal and complete reconstruction of the existing structural concrete pavement is proposed, by developing a ‘Green’ pavement overlay.
A series of laboratory tests have been carried out aiming to improve the workability of fresh and the mechanical properties of the hardened concrete on a series of selected mixes. The initial series incorporated plain (OPC) concrete mix designs prepared with different sources of fine and coarse aggregate obtained from various locations around the UK, to achieve a high Modulus of Rapture (MOR). The addition of Pulverised Fuel Ash (PFA), enhanced the workability and the mechanical properties of the 'plain' mix and the further incorporation of a highly active pozzolanic residue, used for the partial replacement of cement, has yielded the most promising results so far. Third generation superplasticisers and polymers such as glenium C315, styrene butadiene rubber latex (SBR) and poly-vinyl alcohol (PVA) aiming to transform the behaviour of the fresh mix and enhance the mechanical properties of the hardened concrete, are currently implementing the first phase of the investigation.
Additional tests are underway to assess the shear resistance, bond strength and fatigue performance of the material. Also, efforts are directed towards current environmental issues and sustainable, low cost solutions. Hence, the possibility of recycling used polymers and waste obtained from the motor vehicle and aircraft industries is also under investigation.
The paper contains an in-depth discussion of the results from the studies until now and the conclusions drawn from them. A significant number of tables, charts, graphs and diagrams provide a useful supplementary background. Emphasis is given to the experience built up so far, so essential for outlining future work.