摘要
建筑垃圾是在建筑物的建设、维修、拆除过程中产生的固体废弃物。主要包括:废弃混凝土、废弃砖瓦、废弃沥青混凝土以及施工中散落的砂浆和混凝土等。随着建筑业的快速发展,建筑垃圾的总量迅速增加,由于建筑垃圾中的物质再利用耗能大等方面的原因,使得建筑垃圾的应用受到了局限。目前,大部分建筑垃圾的再利用途径为一般性回填和作为建筑物或道路的基础,一方面造成了资源浪费,另一方面还可能造成二次污染。为保护环境、节约资源、发展低碳经济,本文进行了建筑垃圾在水泥生产中的再利用研究。
利用热处理与机械粉碎相结合的方法,将废弃混凝土中的骨料与基质胶凝组分分离,将不同温度热处理下所得的基质胶凝组分按照不同的比例分别作为混合材,应用于水泥中,并进行了对比。结果表明,热处理与机械粉碎相结合,可以实现废弃混凝土中骨料和基质胶凝组分的有效分离,在加热500℃的范围内,随着加热温度的提高,分离效率提高。通过低温煅烧处理,可用由废弃混凝土中分离出来的基质胶凝组分制备具有水化活性的再生胶凝材料,其水化活性与煅烧温度有关。经500℃热处理的基质胶凝组分掺入量为20%时水泥的3d、28d强度与对比试样的强度相差不大,将经适当处理的建筑垃圾分别以10%、15%、20%、25%的比例与常规原料配制成生料,在1450℃下煅烧0.5h烧成熟料,并与用常规生料烧成的熟料进行了性能对比。XRD和SEM观测结果表明,在普通硅酸盐水泥熟料的常规煅烧温度下,以建筑垃圾作原料组分煅烧的水泥熟料,水泥熟料与对比试样的矿物组成相同,熟料中的主要矿物形貌清晰、晶体发育完善;试样3d、28d水化产物的微观结构也与对比试样基本相同。各组配料方案所得熟料的f-CaO含量均在1.5%左右,说明以建筑垃圾为原料组分配制的生料具有较好的易烧性,且水泥熟料的标准稠度需水量与凝结时间正常,安定性良好。当建筑垃圾掺入量为20%时,熟料的28d抗压强度达68.4MPa。
由于建筑垃圾中的SiO_2存有一定的惰性,选择几种碱性激发剂,通过每种激发剂的用量及激发剂效果的不同,找出能提高SiO_2的活性的最优方案。结果表明,各种试样熟料中的f-CaO的含量较低,易烧性较好;熟料的f-CaO的含量随着加入的激发剂量的增多呈减少趋势;随着激发剂的碱性的降低呈增多的趋势。烧成的水泥熟料中矿物清晰,矿物形成质量及力学性能与的激发剂的掺入量及激发剂的碱性强度呈正比。掺入2%NaOH时,试样的矿物形成情况最佳,力学强度最高。
Construction waste was generated in the process of building construction、maintenance、demolition, most of that was the solid waste. It included concrete、abandoned brick、asphalt concrete and construction waste scattered mortar and concrete and so on. With the rapid development of the construction industry, the total amount of construction waste increased rapidly, As in recycling construction consuming large energy, it has been limited tin he application of construction waste. Most of the re-used construction waste for general backfill, as the basis for building or road. It occupies land and may cause secondary pollution. In this paper, using concrete, construction waste burning cement clinker as raw materials for the applications reuse construction waste.
Separating the waste concrete aggregate from matrix bonding used the methods of heat treatment and mechanical. Obtained substrate heated treatment under different temperature as mixed materials according to different ratio of bonding component, and used in cement. The results show that, The combination of heat and mechanical force can be separated the waste concrete aggregate and matrix bonding component effectively. In the context of 500℃, the higher the heating temperature, the separation efficiency. Waste concrete was separated from the matrix composition can prepare the binding materials with hydration activity. The hydration activity related the burning temperature. When heated to 500℃, The results show that, substrate bonding component was 20 percents, the intensity of the samples’3d、28d near the comparison sample. Hydrated minerals formed well observed by XRD and SEM.
Burning cement clinker used construction waste as raw materials, prepared raw materials with construction waste that will be properly handled in the proportion of 10%, 15%, 20%, 25% , fired clinker at 1450℃. In the conventional burning temperature, cement clinker was burned with the components of construction waste as raw materials. The mineral composition of cement clinker the same as ordinary Portland cement observed under XRD and SEM. the appearance of major minerals in the clinker is clear and develop well. The product was observed hydration 3 and 28 days under XRD and SEM. Mineral’s formation and morphology was basically the same with ordinary Portland cement. The content of f-CaO each group clinker was less than 1.5%. The raw material prepared construction waste as raw material components has good burnability. The grade of strength can reach the standards of ordinary Portland cement. When the incorporation of construction waste was 20%, the compressive strength of hydration 28 days was 68.4Mpa.
The application of activator in the process of burning cement clinker used construction waste as raw material. Because there was some inert of SiO_2 in construction waste. Choose some of the activating agent, find the optimal solution that can increase the activity of SiO_2, by the amount of each activator and the effect of different activators. The results show that, the levels of f-CaO was lower in Clinker, the burnabilitywas well. The content of f-CaO showed a decreasing trend as the dose of activator increased, and showed a growing trend with the alkaline of activator was lower. The minerals were clear in cement clinker. The quality of mineral and mechanical properties was proportional to the amount of activator and the alkaline intensity of activator. The compressive strength is highest when the activator was NaOH and the adding ratio is 2%. And the formation of mineral was best when observed By SEM、XRD、EDS.
引文
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