Candidate of low carbon economy concrete: Reinforcing recycled concrete via hybrid fibers

Abstract

Doping fibers are a highly effective method to rescue the weak mechanical properties of recycled concrete (RC). In this study, a complex three-dimensional network structure was constructed by using the unique arrangement and interweaving of three mixed fibers steel fiber (SF), glass fiber (GF), and coir fiber (CF). At the same time, along with the micro-aggregate reaction and pozzolanic reaction of fly ash (FA), the dual advantages of mixed fibers and FA were combined to enhance the mechanical properties of RC, reduce carbon emissions. The effects of FA, SF, GF, and CF on the mechanical properties of RC were discussed using a single-factor test and SEM analysis. An orthogonal test determined the optimal mix ratio, and the synergistic effect of FA, SF, GF, and CF on RC was discussed. Through multiple regression analysis, it was proved the correlation between the compressive strength and flexural strength of hybrid fiber reinforced recycled concrete (HFRC) and FA, SF, GF, and CF. A multiple regression model was proposed to predict the compressive strength and flexural strength of HFRC. Then, HFRC-filled steel tube members were used to measure the bi-directional deviatoric tensile properties to indicate material effectiveness. Finally, the carbon emissions of HFRC are calculated and analyzed. The results show that compared with the control group, the compressive and flexural strengths are increased by 61.68 % and 15.55 % when the mixing ratio is 1 % FA, 2 % SF, 1 % GF, and 1 % CF. The bearing capacity of HFRC-filled steel tube members under bidirectional bias load is 48.2 % higher than that of ordinary concrete-filled steel tube members. Finally, compared to the same dosage of manufactured sand, the use of construction waste groups reduced carbon emissions.