Effects of recycled aggregate combinations and recycled powder contents on fracture behavior of fully recycled aggregate concrete

This paper studied the fracture behavior of fully recycled aggregate concrete (FRAC), which was prepared with 100% recycled coarse and fine aggregates (RCA and RFA) and partial recycled powder (RP). Three-point bending tests on center-notched beams were conducted to evaluate the effects of aggregate combinations and RP contents on the meso-scale fracture mechanism and macro-scale fracture parameters of FRAC. It was found that the FRAC mostly presented transgranular or intergranular failure with RCA or RFA, respectively. The RCA substitution had little effect on the critical crack opening displacements, but the RFA and RP substitution increased and decreased them, respectively. Only the incorporation of RFA led to a reduction of the initial cracking toughness of FRAC. The employment of RAs, especially RCA, reduced the fracture energy G(f) and unstable fracture toughness K-Iu(cn), while the use of RP had a limited impact. The results of the characteristic length showed that RAs made the fracture behavior of concrete more brittle while RP played an opposite role. Both G(f) and K-Iu(cn) reduced with the decrease of tensile strength. The former was remarkable in FRAC due to the variation of aggregate combination whereas the latter was more likely associated with the aggregate size.

Automated summary

This paper studied the fracture behavior of fully recycled aggregate concrete (FRAC), and found that the use of recycled coarse and fine aggregates (RCA and RFA) resulted in different fracture mechanisms. The substitution of RCA had little effect on critical crack opening displacements, while the substitution of RFA and RP increased and decreased them, respectively. The use of recycled aggregates reduced the fracture energy and toughness, while the use of recycled powder had limited impact.