配筋及不配筋再生块体/骨料混凝土的徐变行为

Creep Behavior of Reinforced and Unreinforced Recycled Lump/Aggregate Concrete

为揭示再生块体/骨料混凝土的徐变性能,以再生块体取代率、再生粗骨料取代率、冲洪积土再生砂取代率、荷载比和配筋率为参数,开展了37个再生块体/骨料混凝土试件的受压徐变试验。研究表明:无论配筋与否,再生块体/骨料混凝土的徐变度相比再生骨料混凝土都有所增加,其中不配筋情况下增幅为10.1%,配筋情况下当配筋率为1.16%和1.57%时增幅分别为13.4%和11.5%;随着新混凝土中再生粗骨料取代率从30%增至50%,配筋和不配筋再生块体/骨料混凝土的徐变度都有所增大,增幅分别为7.4%和11.4%;新混凝土的细骨料由河砂全部替换为冲洪积土再生砂,对配筋和不配筋再生块体/骨料混凝土的徐变行为几乎没有影响,但两者的收缩变形均有所减小;随着配筋率从1.16%增大到1.57%,无论是再生骨料混凝土还是再生块体/骨料混凝土的徐变度都随之减小,减幅分别为5.0%和6.6%;配筋使得再生骨料混凝土和再生块体/骨料混凝土的收缩变形都有所降低,且随配筋率升高降幅扩大;随着新混凝土中再生粗骨料取代率从30%增至50%,再生块体/骨料混凝土的弹性模量变化不大;新混凝土的细骨料由河砂全部替换为冲洪积土再生砂,对再生块体/骨料混凝土的弹性模量几乎没有影响;荷载比不超过0.4时,可近似认为再生块体/骨料混凝土的徐变度与荷载比无关。

Compressive creep tests on thirty-seven recycled lump/aggregate concrete(RLAC)specimens were car⁃ried out to reveal the creep behavior of RLAC by taking the replacement ratio of demolished concrete lumps(DCLs),replacement ratio of recycled coarse aggregates(RCAs),replacement ratio of recycled sand rooted from alluvialproluvial(A-P)soil,stress level and reinforcement ratio as parameters.The results show that the specific creep of reinforced/unreinforced RLAC is greater than that of reinforced/unreinforced recycled aggregate concrete(RAC).The increase rate of RLAC is 10.1%when unreinforced and the increase rate is 13.4%and 11.5%when the reinforce⁃ment ratio is 1.16%and 1.57%,respectively.As the replacement ratio of RCAs in new concrete increases from 30%to 50%,the specific creep of reinforced/unreinforced RLAC increases by 7.4%and 11.4%respectively;when the fine aggregate(i.e.,river sand)of new concrete is completely replaced by the recycled sand from A-P soil,the creep behavior of reinforced/unreinforced RLAC shows almost no change,but both of the shrinkage deformation decrease.As the reinforcement ratio increases from 1.16%to 1.57%,the specific creep of RLAC and RAC de⁃crease by 5.0%and 6.6%,respectively.Reinforcement reduces the shrinkage deformation of RAC and RLAC,and the reduction grows with the increase of reinforcement ratio.As the replacement ratio of RCAs in new concrete in⁃creases from 30%to 50%,the elastic modulus of RLAC have little change and it is also almost free from the impact of replacing the fine aggregate(i.e.,river sand)of new concrete with the recycled sand from A-P soil;and when the stress level is less than 0.4,the specific creep of RLAC is nearly deemed as irrelevant to the stress level.