Recycled industrial waste in concrete composite pavement.

Abstract

Composite concrete pavement has a longer serviceable lifetime compared to other pavement types. The increase in material and construction costs are mitigated by using a low cost concrete in the lower lift of the pavement. The two cost lowering measures discussed in this report are the use of recycled concrete aggregates and lowering the portland cement content through supplemental materials including fly ash and lime softening residuals. Recycled concrete aggregate concrete plastic and hardened properties are greatly improved when a two-step industrial sized crushed is used for the production of the recycled aggregates. Recycled concrete workability issues can be mitigated and the compressive strength increased by using a technique called internal curing from soaking the recycled aggregates till saturated. The portland cement can be partially replaced by fly ash and a water treatment byproduct called lime softening residual. The lime softening residuals increase the strength gain rate of the fly ash concrete. The assumed vehicle of this increase is the availability of hydrated lime for the fly ash particles. Both methods of lowering concrete cost show little to know change in the overall strength of the concrete and therefore may make composite pavement in the United States more viable.