| At present,with the rapid growth of the demand for concrete in the construction industry and the lack of sand and gravel resources,resulting in short supply of sand and stone resources,a large price rise,with green environmental protection,resource recycling and other characteristics of the recycled concrete aggregate is used to replace the natural sand and gravel to join the use of new mixed concrete,is defined as recycled aggregate concrete.As recycled concrete aggregates with micro cracks,the old mortar initial defects such as large porosity,makes the durability of recycled aggregate concrete structure problem more prominent,especially in the cold area,recycled aggregate concrete under freeze-thaw cycles is reinforcement corrosion problem is more serious,performance and reinforced material recycled aggregate concrete frost resistance corrosion resistance is an important way to solve this problem.Based on this,the research puts forward will have capillary water pressure regulation effect of vitrified beads in recycled aggregate concrete preparation has good performance of recycled aggregate thermal insulation concrete,with basalt fiber reinforced(BFRP)instead of steel to achieve the above purpose,and regeneration of recycled aggregate thermal insulation concrete under freeze-thaw cycles and good bonding performance between BFRP reinforcement is the guarantee of recycled concrete aggregate and the premise of BFRP reinforcement is applied to the freezing cold areas.This paper mainly studied the regeneration of recycled aggregate thermal insulation concrete under different recycled coarse aggregate replacement ratio of antifreeze performance and under different freeze-thaw cycles with BFRP bond properties of elastic,and comparative study of four different types of concrete after freeze-thaw cycle of bond performance degradation rule,with the improved BPE model of regenerative recycled aggregate thermal insulation concrete and the bond-slip relationship between BFRP reinforcement for fitting,concrete research content and conclusions:(1)Study on mechanical properties of recycled aggregate thermal insulation concrete after freeze-thaw.In this paper,by setting different replacement rates of recycled concrete aggregate(0%,30%,50%),the effects of recycled concrete aggregate on the mechanical properties of recycled aggregate concrete and recycled aggregate thermal insulation concrete after freezing and thawing were studied.The study showed that with the increase of freezing and thawing times,the compressive strength and splitting tensile strength of recycled concrete and recycled thermal insulation concrete decreased.With the increase of recycled concrete aggregate content,the loss of compressive strength and tensile strength of concrete after freeze-thaw increased,but the increase range was less than 3%,and the influence was not significant.After 200 freeze-thaw cycles,the recycled aggregate concrete has lost its bearing capacity,while the recycled insulated concrete still has 68.2%,54.8%and 55.2%of residual compressive strength.The addition of glazed hollow beads significantly improves the freezing resistance of recycled concrete.(2)Study on frost resistance of recycled aggregate thermal insulation concrete.By studying NC,RAC,TIC and RATIC under 8 different freeze-thaw cycles of 0,25,50,75,100,150,200 and 300 times,the change rule of mass loss rate,relative dynamic modulus of elasticity and durability coefficient of four kinds of concrete were obtained.When the number of freeze-thaw cycles is 150,the relative dynamic elastic modulus of RAC(30)decreases to55.38%,and the durability coefficient is only 27.69%,indicating that the specimen has lost its frost resistance.The relative dynamic elastic modulus and durability coefficient of RATIC(30)and RATIC(50)are 73.66% and 46.89,respectively.71.22%,47.83%,good frost resistance.The frost resistance of NC,RAC,TIC and RATIC was determined by analysis.The specific relationship was as follows: TIC>RATIC>NC>RAC.(3)Study on the bonding properties of BFRP bars and recycled aggregate thermal insulation concrete after freeze-thaw cycles.Through different freeze-thaw cycles,the BFRP muscle recycled aggregate thermal insulation concrete center pull-out test,when the freezing and thawing cycles of 0,50,100,200,the NC,RAC,TIC and RATIC through the contrast test,the failure modes of concrete specimens,and study its role in rapid freezing and thawing cycles after degradation law of bond performance,analysis of the ultimate bond strength,peak slip,such as evaluation index of bond properties relative bonding strength with the degradation law of freeze-thaw cycles,NC,RAC and RATIC failure mode and bonding degradation rule of basic similar,With the increase of the number of freeze-thaw cycles,the failure mode will change from pull-out failure to pull-splitting or splitting failure,and TIC specimens are always pull-out failure.(4)Study on the bond slip constitutive relationship between BFRP bars and recycled aggregate thermal insulation concrete.Based on the existing bond-slip constitutive model and the measured τ-s curve fitting,found improved BPE model can well reveal the BFRP bar-recycled concrete,the bond-slip relationship of concrete under different freezing and thawing times obtained BFRP bar-recycled concrete concrete bond-slip model parameters of the model,established a BFRP bar and RATIC bond-slip constitutive model,the fitting results show that the improved BPE model can better describe the BFRP bar-regenerative thermal insulation of concrete bond-slip curve. |
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