In finished PCC pavements, over-consolidation may occur if the mix is not properly designed. Over-consolidation is noted when longitudinal trails can be visually observed in the surface. These "vibrator trails" run parallel to each other with spacing similar to that of the vibrators on pavers. Cores taken from vibrator trails have revealed many instances where the hardened concrete contains less than 3% air, rather than 6%-7% as designed, thus significantly reducing concrete freeze-thaw durability. Although measures can be taken to monitor the frequency of vibrations, vibrations are still inevitable. It would be a revolutionary advancement in paving technology if the vibration of pavement concrete could be eliminated.

The goal of the proposed research is to develop a new type of self-consolidating concrete (SCC) for slip form paving. It is envisioned that SCC will produce more workable concrete and smoother pavements, better consolidation of the plastic concrete, and higher rates of production.

Based on the promising results of Phase I, additional study is proposed to refine the mix design of SCC for slip-form paving and apply the new SF SCC in the field. The research team believes that a desirable balance between compactibility and green strength or shape-holding ability of a concrete mixture may be achieved by carefully balancing concrete materials and mix design. The new SF SCC will (1) be workable enough for machine placement, (2) be self-compacting with minimum segregation, (3) hold shape after extrusion from a paver, and (4) have performance properties (strength and durability) compatible to current pavement concrete.

Phase I, the feasibility study, has been completed. New participants are needed for phase 2 of the project - the field study. For more information, see the Phase 2 Work Plan. $30,000 total commitment requested over 2-3 years. Lesser contributions can be considered. Travel for TAC members will be paid from the pooled fund.