Recycled Aggregate Concrete with Industrially Pre-carbonated Recycled Concrete Aggregates and Low Clinker Content

Recycled aggregate concrete (RAC) was produced with industrially pre-carbonated recycled concrete aggregates (RCA). The clinker content was reduced by substituting Portland limestone cement and Portland cement with limestone and phonolite powder. Concrete RCA was compared to a reference concrete (NAC) produced with natural concrete aggregates and without clinker reduction. The reduction of water-to-powder ratio in the clinker-reduced concrete RAC allows to surpass the compressive strength of concrete NAC and to partly compensate for the increase of carbonation and chloride migration coefficients. However, the ratio of E-modulus to compressive strength is decreased in concrete RAC. While shrinkage is only marginally affected by the use of RCA and clinker reduction, the creep coefficient is decreased. The resulting concrete properties show that the cement clinker is utilized in a more efficient way when ground limestone and natural pozzolan (phonolite) powders are combined with Portland cement instead of Portland limestone cement. In particular, compressive strength, carbonation resistance and chloride resistance are all improved.