| The urban and rural modernization construction in China continues to develop,the demand for natural sand and stone is high and the use cost is increasing.The recycled aggregate obtained by recycling construction waste has low strength and large porosity,which hinder the resource utilization of construction waste and the reduction of supply and demand pressure of natural sand and stone.Geopolymer concrete has good interface bonding ability with aggregate,which can be better combined with recycled aggregate attached to mortar to make up for strength defects.It is difficult to recycle tailings due to large reserves and quality differences.The tailings with high silicon and aluminum content can be used as raw materials for preparing geopolymer concrete.Therefore,lead and zinc tailing powder mixed into geopolymer concrete using recycled coarse aggregate(GRC-LZT)can complement advantages and accelerate the resource utilization of solid waste.Compared with portland ordinary cement concrete,geopolymer concrete has the characteristics of fast hardening and early strength,poor ductility and high brittleness.GRC-LZT uses materials coming from a wide range of sources and varieties.The good bonding and collaborative work with steel bars are the foundation of engineering application,which needs to be recognized and analyzed through tests.This paper mainly includes the followings:(1)Experimental study on properties of raw materials and geopolymer slurry.The physical characteristics and performance of GRC-LZT raw materials were tested.The water demand of lead-zinc tailings is smaller than that of slag powder and fly ash,and the impact on the compressive properties of geoparmer slurry is greater than the impact on the bending properties.(2)Experimental study and theoretical study on basic mechanical properties of GRC-LZT.Taking the replacement rate of lead and zinc tailings(K),replacement rate of reclaimed coarse aggregate(R)and water-solid ratio as variables,17 groups of mixing ratios were designed.The cubic compressive strength fcu,7d of GRC-LZT can reach 73.07%～87.79%of fcu,28d.The relationship between curing age and fcu was studied and the prediction formula of early strength ratio was obtained:fcu,T/fcu,28d=0.188ln(T)+0.398.Establish the theoretical formulas between fcu and fc,ft,ff,and Ec:fc=0.8764fcu,ft=0.0715fcu,ff=0.0878fcu,Ec=105/(1.09+125.90÷fcu).Six groups of specimens were selected for SEM photography and and it was found that the microstructure was consistent with the macroscopic strength.(3)Experimental study and theoretical research on bonding properties between steel bar and GRC-LZT.Taking 17 groups of mix ratio,steel surface characteristics,steel diameter and steel bond length as variables,the center drawing test was carried out on 22 groups of 66 drawing test blocks.GRC-LZT can have better bonding performance with steel bar when adopting 15%LZT,100%RCA,0.45 water solid ratio.The formula of ultimate bonding strength is established:τu=(0.14+1.89/la/d)(3.06c/d)ft.A constitutive model of bond-slip curve suitable for GRC-LZT was obtained.(4)ABAQUS finite element modeling and analysis of bonding performance between steel bar and GRC-LZT.The bond slip curves measured in the drawing test and simulated by ABAQUS were compared and analyzed.The load transfer law and bond failure situation of GRC-LZT splitting failure and steel bar pulling failure were visualized. |
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