Hybrid self-compacting concrete incorporating ceramic waste and recycled aggregates

Abstract Self-compacting concrete offers significant advantages in terms of ease of placement, reduced construction time, and improved quality control. However, its production typically requires higher amounts of cement and chemical admixtures. At the same time, the valorisation of construction and demolition waste has emerged as a key strategy to reduce environmental impacts and promote circular economy practices in the construction sector. In accordance with the above, this study presents the design and evaluation of a hybrid SCC incorporating ceramic waste and recycled aggregates, combined with an alkali-activated cementitious matrix as a sustainable alternative. Two concrete systems were developed in this study: a reference mixture containing Portland cement and ceramic filler, and a sustainable mixture incorporating 85% alkali-activated ceramic waste. For each system, were used natural coarse aggregates (NCA) and recycled coarse aggregates (RCA). The self-compacting performance of the mixtures was evaluated through of Slump flow test, V-funnel test and L-box test. Mechanical properties (compressive strength, splitting tensile strength, and flexural strength) and physical properties (density, absorption, and percentage of permeable voids) were also evaluated. The alkali-activated mixture with recycled aggregates exhibited values of 770 mm, 5 s and 0.99, respectively; these results indicate excellent flowability, passing ability, and resistance to segregation. The compressive strength was superior compared to the reference system, 28 MPa and 24 MPa with NCA and RCA, respectively. Although the use of recycled aggregates slightly reduced strength, the values remained within ranges suitable for structural applications. The results confirm the technical feasibility of producing self-compacting hybrid concretes based on alkali-activated ceramic waste and recycled aggregates.