生活垃圾焚烧尾渣-次轻混凝土冻融劣化特性及微观机制

Freeze-thaw deterioration characteristics and micro-mechanism of solid waste incineration tailings and specified density concrete

针对混凝土在冻融环境中耐久性差及传统改善方法引起的成本问题,提出利用城市生活垃圾焚烧尾渣作为轻骨料,制备能够提高抗冻性降低成本的次轻混凝土。以水胶比0.3,尾渣轻骨料掺量为25wt%、50wt%和75wt%的次轻混凝土为研究对象,模拟严寒地区冻融环境。利用剥落量、质量损失、强度损失、动弹性模量损失等宏观指标探究次轻混凝土冻融劣化规律,从次轻混凝土吸水饱和度、孔结构特征、骨-浆界面等方面揭示了冻融劣化机制,最后建立基于损伤力学理论的次轻混凝土损伤劣化模型。结果表明:冻融循环侵蚀对普通混凝土造成的耐久性损伤程度比次轻混凝土更严重,普通混凝土表面产生了更多的砂浆剥落。尾渣轻骨料的掺入能够显著改善混凝土的抗冻性能。在冻融循环侵蚀条件下掺入25wt%、50wt%和75wt%尾渣轻骨料的次轻混凝土耐久性能分别比普通混凝土至少提高了15.2%、30.3%和33.3%。次轻混凝土的内养护作用加强、有益孔的数量增加和骨-浆界面强度增大等改善了孔隙结构和界面特征,提高了冻融侵蚀耐久性能。基于损伤力学建立的次轻混凝土劣化模型的拟合度为0.97以上,能够较好地研究次轻混凝土冻融变化规律和损伤程度。

In view of the poor durability of concrete in freezing-thawing environment and the cost problems caused by traditional improvement methods,municipal solid waste incineration tailing was used as lightweight aggregate to prepare specified density concrete which can improve the frost resistance and reduce the cost.Taking the lightweight concretes with water-binder ratio 0.3 and tailing lightweight aggregate content of 25wt%,50wt%and 75wt%as the research objects,the freeze-thaw environment in severe cold regions was simulated.The freeze-thaw deterioration law of specified density concrete was explored by macro-indices such as spalling amount,mass loss,strength loss and dynamic elastic modulus loss,and the freeze-thaw degradation was revealed from the aspects of water absorption saturation,pore structure characteristics and bone-grain interface of specified density concrete.Finally,a damage degradation model for light concrete was developed using the damage mechanics theory.According to the findings,the durability damage of ordinary concrete caused by freeze-thaw cycle erosion is more serious than that of specified density concrete,and more mortar peeling occurs on the surface of ordinary concrete.The frost resistance of concrete can be considerably increased by the inclusion of tailing lightweight aggregate.Under the condition of freeze-thaw cyclic corrosion,the durabilities of the specified density concretes mixed with 25wt%,50wt%and 75wt%tailing lightweight aggregate are improved by 15.2%,30.3%and 33.3%higher than that of ordinary concrete,respectively.The porosity structure and interface characteristics of the specified density concrete are improved by strengthening the internal curing function,increasing the number of beneficial pores and increasing the strength of the bone-slurry interface,and the freeze-thaw erosion durability is improved.The freeze-thaw change rule and damage degree of specified density concrete may be studied more thoroughly thanks to the specified density concrete degradation model's fitting degree based on damage mechanics,which is above 0.97.