Control of Interface Structure between Cement Paste and Waste-Derived Aggregates

利用烧结污泥、城市垃圾焚烧灰、烧结粉煤灰、玻璃屑等废源骨料制备了大容量再生废混凝土（HVRWC），并与天然骨料制备的普通混凝土进行了对比。采用城市垃圾焚烧灰生态水泥代替普通硅酸盐水泥（NPC）。随着废骨料掺量的增加，混凝土的抗压强度降低。这是由于粗大的孔隙和水泥浆体与骨料之间的低粘接强度造成的。含631kg/m3废骨料的HVRWC在91天龄期表现出超过40 N/mm2的高强度，可应用于建筑材料。HVRWC的水化过程与天然骨料的水化过程相似，没有观察到废物衍生材料的危害。高炉段塞和粉煤灰的联合使用，通过消耗Ca(OH)2，促进C-S-H的形成，使混凝土结构随着龄期的增加而致密化。HVRWC的硬化结构与天然集料的硬化结构差异不大。耐久性相当，并且没有观察到有害物质从混凝土中洗脱。SEM和EPMA观测结果表明，在W/C=0.5时，ecoement未形成过渡带。Ecocement膏体与骨料的接触状况优于NPC。与标准砂骨料相比，烧结后的污泥具有较低的粘结强度和较高的孔隙率，这是由于骨料表面光滑所致。研究结果表明，水泥浆体与废骨料之间的界面结构可以通过使用消耗Ca(OH)2的多水合成水泥（如Ecocement）来控制。

High-volume recycled waste concrete (HVRWC) was prepared by utilizing waste-derived aggregates such as sintered sewage sludge, incineration ash of urban refuse, sintered coal ash and glass cutlet, and compared with the ordinary concrete from natural aggregates. Ecocement from incineration ash of urban refuse was also used instead of normal Portland cement (NPC).The compressive strength of concrete was decreased with increasing the mixing ratio of waste-derived aggregates. This is attributed to the low strength of waste-derived aggregates owing to coarse pores and the low adhesive strength between cement paste and the aggregates. The HVRWC including 631kg/m3 of waste-derived aggregates showed high strength more than 40 N/mm2 at the age of 91 days, which can be applied to construction materials.The hydration in HVRWC proceeded similarly to that of natural aggregates, and no mischief owing to wastederived materials was observed. The combined use of blast-furnace slug and fly ash allowed the densification of concrete textures with age, by consuming Ca(OH)2 and promoting the formation of C-S-H.The hardened structure of HVRWC did not show great difference from that of the natural aggregates. The durability was comparable, and the elution of the harmful species from the concrete was not observed.SEM and EPMA observations indicated that the transition zone did not form at W/C=0.5 when Ecocement was used. The contact between Ecocement paste and aggregates was in better conditions than the NPC.The sintered sewage sludge showed lower adhesive strength and rather higher porosity than the standard sand aggregate, which is ascribable to the smoothness on the surface of the aggregate. It was suggested that the interface structure between cement paste and waste-derived aggregate could be controlled by using Ca(OH)2-consuming and polyhydrates-forming cement such as Ecocement.