Self-compacting concrete containing coarse recycled precast-concrete aggregate and its durability in marine-environment-related tests

Abstract

Marine environments are extremely challenging for the long-term durability of concrete. Prior validation of concrete durability is therefore a prerequisite to guarantee its adequate performance under marine environmental conditions. In this study, the performance of Self-Compacting Concrete (SCC) with variable contents of coarse Recycled Precast-Concrete Aggregate (RPCA) and two different cement contents is assessed in terms of capillary water absorption, natural and accelerated carbonation, resistance to SO2 attack, and moist/dry performance in drinking water, marine water, and sulfate water. These tests are intended to simulate the conditions of a marine environment. In general, the results showed that an SCC containing coarse RPCA of adequate durability under marine conditions could be produced. On the one hand, porosity due to the presence of RPCA increased less as the cement content was increased, which in turn reduced water absorption and SCC carbonation. For example, the effective porosity of the SCC was reduced by 25 % between day 28 and day 180, following the addition of 100 % coarse RPCA. On the other hand, both the SO2-attack and the moist/dry tests revealed that the weight of the SCC with RPCA underwent greater variations, due to the reactions of the cement-hydration products with chlorides and sulfates, as well as salt deposition. However, SCC compressive strength was never adversely affected, as the concrete strength increased up to 8 MPa after the drinking-water and the sulfate-water moist/dry tests when using RPCA. According to both Fick's and Parrot's models, the projected service life of all the mixes was over 100 years, regardless of the coarse RPCA content, making this sort of SCC a feasible option for construction in marine environments.