磷渣微粉对再生混凝土性能的影响研究

Influences of phosphorous slag as cement replacement on the performances of recycled aggregate concrete

为了提升再生骨料混凝土的工作性能、探讨工业废渣的有效利用,采用磷渣微粉取代部分水泥配置再生混凝土,并试验测试了不同混凝土的强度、变形曲线和氯离子渗透系数,分析了磷渣微粉对再生混凝土及其内部砂浆和界面力学性能以及耐久性能的影响。再生混凝土的试验研究结果表明:与普通混凝土相比,由于磷渣的缓凝作用使得磷渣混凝土早期强度有所下降,变形略大,但是90 d时由于磷渣微粉的火山灰效应使得不同再生骨料掺和率的再生混凝土强度和耐久性都有很大的提高。磷渣微粉对水泥砂浆的物理力学性能提升很大,磷渣砂浆的有效氯离子扩散系数仅为普通砂浆的1/5。同时,再生混凝土新界面的抗拉强度试验结果也表明:磷渣微粉能够增强界面的黏聚力。此外,还根据再生与普通混凝土界面的SEM形貌和能谱图,分析了磷渣改性再生混凝土的细微观机理,研究结果表明磷渣微粉能够有效改善再生混凝土内孔隙结构和排列,消耗氢氧化钙,生成C-S-H凝胶和钙矾石,提高材料密实性和强度。

To improve the performance of recycled aggregate concrete（RAC） and make an effective use of industrial waste,superfine phosphorous slag（PHS） were adopted as cement replacement in this study to modify the RAC.The influences of PHS on the mechanical properties and durability of RAC,mortar and interfacial transition zone（ITZ） were discussed based on the test results of concrete strengths,stress-strain curve and chloride diffusion coefficient.The experimental results showed that the PHS decreased the early strength and increased the deformation of slag RAC due to its retarding effect.However,it improved the strength and durability of RAC at 90 days due to the pozzolanic activity of PHS.The PHS enhanced the physical and mechanical properties of mortar,and the effective chloride diffusion coefficient of mortar containing PHS was only 1/5 of the ordinary mortar.Meanwhile,the tensile strength of ITZ in RAC also illustrated that the PHS made a great contribution to the adhesive force of ITZ.In addition,the improving micromechanism of RAC by PHS was investigated by energy dispersive spectrometry（EDX） and scanning electron microscope（SEM）.The microstructure and the composite analyses showed that the PHS can modify the structure and the arrangement of pores in concrete by consuming the calcium hydroxide.The generation of C-S-H gel and ettringite enhanced the density and strength of RAC.