Experimental study on mechanical properties of reclaimed concrete strengthened by nano-Sio2
In order to improve the performance and quality of the regenerated aggregate,nano-SiO2 with different mass fractions and strengthening times were used to impregnate and strengthen the regenerated aggregate.The recycled concrete was prepared with the recycled aggregate before and after strengthening,and a uniaxial compression test was carried out.The stiffness of the loading system was increased by the rigid auxiliary frame,and the descending section of the stress-strain curve of the recycled concrete was successfully collected.The geometric characteristics of the stress-strain curve equations of different forms were analyzed theoretically,and a function model suitable for the uniaxial compression constitutive relation of recycled concrete was selected by fitting the theoretical equation with the test curve.According to the change of aggregate properties before and after strengthening,it was concluded that the quality of reclaimed aggregate improved best when the mass fraction of nano-SiO2 was 2％and the reinforcement was 48 h.Analysis of the experimental stress-strain curve shows that the upward section of the curve has a high degree of overlapping,while the downward section of the curve has a certain dispersion due to the different replacement rates of recycled aggregates.Nano-SiO2 can increase the peak stress of recycled concrete with a water-binder ratio of 0.5 by 13.1％～24.0％,and the average elastic modulus by 44.5％.The water-binder ratio of 0.35 in the experimental group increased significantly due to the different regenerated aggregate replacement rate.It is concluded that the piecewise function proposed by Guo Zhenhai satisfies all the geometric characteristics of typical curves and has a high fitting degree with the test curve.
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