Performance of lightweight aggregate concrete containing slag after 25 years in a harsh marine environment

This paper reports the results of a study on concretes containing lightweight aggregate (LWA) retrieved from the tidal zone of a marine exposure site. In terms of chloride resistance, the LWA concrete performed equivalently to similar concretes of the same age produced with normal density aggregate that were retrieved from the same site 2 years earlier. The partial replacement of Portland cement with slag led to substantial reductions in chloride penetration and the chloride diffusion coefficient. However, at w/cm ≥ 0.50, the incorporation of slag resulted in increased surface deterioration (scaling) attributed to freezing and thawing. Concrete with LWA, silica fume and w/cm = 0.33, showed better-than-expected performance with regard to resistance to chloride-ion penetration and it is speculated that this may be partly attributed to “internal curing” provided by the LWA which reduces the impact of self desiccation. Further studies are needed to confirm this phenomenon.