再生粗骨料品质与掺量对再生混凝土抗冻融性能影响规律

摘要

There exists surface-attached cement stone,and high water absorption rate for recycled aggregate (RA),which leads to poor mechanical behavior when comparing to natural aggregate.The influence of recycled coarse aggregate with different quality and loading on the freezing and thawing durability property of the corresponding recycled concrete is also frequently paid attention for engineering projects located in the northern region.Employing the fast freezing and thawing method,the frost resisting properties of ordinary aggregate concrete (OAC),high-quality recycled coarse aggregate concrete (HRAC),and normal-quality recycled coarse aggregate concrete (NRAC) are compared and analyzed.Meanwhile,the influence of quality and addition of RA on the frost resistances of RAC after varied freezing and thawing times,basing on mass loss rate and relative dynamic elastic modulus.The results show that,in terms of the anti-frosting capacity,the order from high to low is OAC>HRAC>NRAC.After 250 freeze-thaw cycles,the mass loss rate of NRAC is 5.36% ,and relative dynamic elastic modulus of NRAC is less than 60% when the RA addition is 100% ,and cannot meet the requirement of F250.%与天然骨料相比,再生骨料表面附着一些硬化水泥块,相应吸水率较大,进而导致其机械强度较低.不同品质及掺量的再生粗骨料(RA)对相应再生混凝土的抗冻耐久性也是北方地区工程常关注的问题.采用快速冻融法对比研究了普通骨料混凝土(OAC)、优质再生粗骨料混凝土(HRAC)、正常质量的再生粗骨料混凝土(NRAC)的抗冻性能,同时结合质量损失率、相对动弹性模量变化研究了RA的品质及掺量对不同冻融循环次数下RAC抗冻性能的影响规律.试验表明,抗冻融破坏能力高低顺序为OAC>HRAC>NRAC;经过250次冻融循环后,NRAC的质量损失率达5.36%,RA掺量为100%时,NRAC相对动弹性模量低于60%,不满足F250要求.