Development of waste-based concretes containing foundry sand, recycled fine aggregate, ground granulated blast furnace slag and fly ash

In recent years, the use of fly ash (FA) and ground granulated blast furnace slag (GGBS) as cement replacement materials as well as foundry sand (FS) and recycled fine aggregate (RFA) as sand replacement materials has provided an attractive avenue toward a green construction material for decreasing the effect of concrete and construction and demolition (C&D) waste on the environment. The behavior of concrete produced with a combination of FS/RFA and FA/GGBS is presented in this paper. 17 concrete mixes were prepared, and tests were undertaken to assess workability, density, compressive, splitting tensile and flexural strength, elastic modulus and water absorption of each mix. It is shown that an increase in the FS and RFA content up to 100% causes a decreased compressive strength of concrete. However, concrete containing RFA at 25% sand replacement experiences a slightly higher compressive strength in comparison to conventional concrete. Replacement of cement with FA at different levels has a negative impact on the concrete strength, whereas cement replacement with 23% FA and 47% GGBS results in a higher concrete strength in comparison to that of the companion cement-based concrete with the same sand replacement level. The results also show that replacement of sand with FS and RFA at up to 25% leads to a nearly identical elastic modulus compared to that of the conventional concrete. Although elastic modulus of FA mixes is lower in comparison to that of conventional concrete, GGBS and ternary (combination of FA and GGBS) mixes provide nearly close elastic modulus to conventional concrete. Sand replacement with FS at up to 50% in concrete results in a similar water absorption to the conventional concrete. It is shown that GGBS and ternary mixes experience a lower water absorption compared to the conventional concrete. These findings indicate that the mix design technology used in the present study offers a significant potential to produce concretes with a reduced environmental impact.