Seyedhamed Sadati

Can Concrete Containing High-Volume Recycled Concrete Aggregate Be Durable?

This paper evaluates the effect of recycled concrete aggregate (RCA) on concrete durability. Six RCA types procured from different sources were employed at 30 to 100% replacement rates by volume of virgin coarse aggregate. One fine RCA was also investigated and was used for up to 40% replacement by volume of virgin sand. In total, 33 mixtures were proportioned with these aggregates in concrete made with a binary or a ternary binder system and a watercementitious materials ratio (w/cm) of 0.37 to 0.45. The mixtures were investigated for frost durability, electrical resistivity, sorptivity, and abrasion resistance. Test results indicate that concrete made with up to 100% coarse RCA from an air-entrained source can exhibit proper frost durability. No significant reduction (limited to 3%) in frost durability factor was observed when the fine RCA volume was limited to 15% of total sand. Increase in mass loss due to deicing salt scaling was observed in concrete made with 50% of RCA with high (over 4%) deleterious materials content and high mass loss during soundness test. For a given w/cm and binder type, the use of 50% coarse RCA resulted in up to 32% reduction in electrical resistivity. The reduction in w/cm from 0.40 to 0.37 and the use of ternary binder containing 35% Class C fly ash and 15% slag proved to be effective in mitigating the potentially negative impact of RCA on sorptivity and abrasion resistance, compared to concrete made without any RCA with w/cm of 0.40 and binary cement with 25% fly ash.

Long-Term Performance of Silica Fume Concrete in Soil Exposure of Marine Environments

AbstractGiven the time-dependent microstructural modifications in cement matrix, long-term monitoring of concrete in natural exposures will be necessary. The present research addresses the long-ter...