Long‐term behavior of sustainable self‐compacting concrete with high volume of recycled concrete aggregates and industrial by‐products

Abstract

The addition of recycled concrete aggregates together with industrial by-products for the concrete production is an effective solution to the environmental problems in terms of excess waste materials and massive nonrenewable natural resources consumption. This article investigates the long-term behavior and microstructure of sustainable self-compacting concrete (SCC) by substantially substituting natural coarse aggregate with recycled coarse aggregates (RCA) and cement with supplementary cementitious materials (SCM). The influences of RCA and SCM content as well as SCM combination type (fly ash, ground granulated blast furnace slag and/or silica fume) on the mechanical properties and long-term deformation of recycled aggregate SCC (RA-SCC)were assessed in detail. Furthermore, scanning electron microscope and x-ray diffraction were implemented to justify the reasons for improvement on mechanical properties and long-term behavior of RA-SCC. The results indicate that the addition of RCA reduces the compressive strength and elastic modulus of RA-SCC, and increases the creep and shrinkage deformations. However, incorporating SCM with a combination of fly ash, ground granulated blast furnace slag and silica fume compensates for the detrimental effect of RCA and makes considerable improvement in strength and reduction in the long-term deformations. Microstructure analysis confirms the reasons of improvement, which is mainly attributed to the addition of SCM by adopting a combination type, resulting in a more compact microstructure such as stronger interfacial transition zone. Based on the experimental results, the correction factors of RCA and SCM were introduced in conjunction with fib Model Code 2010 model to evaluate the creep coefficient of RA-SCC.