Bond behavior of concrete with coarse and fine recycled aggregates from construction and demolition waste

While the construction sector faces rising CO 2 emissions and depletion of natural resources, the use of construction and demolition waste (CDW) as recycled aggregates (RA) offers a promising route towards more sustainable concretes. However, further studies on the structural behavior and design of recycled aggregate concrete (RAC) are required, especially for higher strength classes and clinker-efficient binders. This study evaluates RAC produced with coarse and fine RA from CDW and a clinker-efficient cement (CEM III/A). Five mixes with a total RA replacement ratio of α RA = 45 % and target strength classes C30/37 and C50/60 were designed and tested. Workability and hardened properties (compressive and splitting tensile strength, elastic modulus) were determined and compared to corresponding concrete with natural aggregate (NAC) mixes. Bond behavior to ribbed steel rebars with diameters ∅ 10 mm and ∅ 16 mm was investigated in 33 tests using a beam-end test setup. The RAC with α RA = 45 % achieved the target C50/60 strength class and exhibited fresh and hardened properties comparable to the NAC references. When only coarse RA were used, normalized ultimate bond stresses were similar to those of NAC for both bar diameters. The inclusion of fine RA mainly affected the initial bond stiffness. Crack patterns remained comparable, with slightly earlier crack initiation in RAC. Design anchorage length formulations in fib Model Code 2020 and FprEN 1992 led to conservative results for all mixes. The findings demonstrate that structurally efficient, higher-strength RAC with clinker-efficient cement can be produced at industrially relevant replacement levels without compromising bond performance, supporting the wider use of RAC in reinforced concrete structures.