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

利用城市污泥、城市垃圾焚烧灰、粉煤灰和玻璃碎片等废弃物骨料制备大掺量再生混凝土，并与普通天然骨料混凝土进行对比。采用城市垃圾焚烧灰生态水泥代替普通波特兰水泥（NPC），混凝土的抗压强度随着垃圾衍生骨料掺量的增加而降低。这是由于废物衍生骨料的强度低，由于粗孔和水泥浆体和骨料之间的粘合强度低。含631 kg/m3废弃物骨料的HVRWC 91天强度大于40 N/mm ~ 2，可用于建筑材料，其水化过程与天然骨料相似，未发现废弃物骨料的危害。高炉矿渣和粉煤灰的联合使用允许混凝土的纹理致密化随着年龄的增长，消耗Ca（OH）2和促进C-S-H的形成。HVRWC的硬化结构没有表现出很大的差异，从自然集料。SEM和EPMA观察表明，当W/C=0.5时，使用Ecocement时，没有形成过渡区。生态水泥浆体与集料的接触状况比NPC好，烧结污泥与集料的粘结强度比标准砂集料低，孔隙率比标准砂集料高，这与集料表面光滑有关。研究表明，采用消耗Ca（OH）2、形成多水化合物的水泥，如Ecocement，可以控制水泥浆体与垃圾衍生骨料之间的界面结构。

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.