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Characterization of ammonia gas release from concrete added with ammoniated fly ash

机译：掺有氨化粉煤灰的混凝土释放氨气的特性

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摘要

To characterize the release of ammonia (NH3) from ammoniated fly ash in concrete, laboratory experiments were carried out with concrete added with fly ash containing ammonium loading ranging from 65 to 3,200 mg NH4 +/kg fly ash. A physical description of the NH3 release from concrete was given, and a quantitative diffusion model was developed. In the experiments, NH3 gas release lasted 5 days to 3 weeks. After the ammonia gas release rate gradually decreased to a non-detectable level, there was still 20 to 70 % of ammonium retained in the concrete. Of all the NH3 gas released, over 80 % was emitted in the first 8 h after the concrete was mixed. According to the physical and chemical condition of the concrete, NH3 release from concrete was divided into three periods: mixing, initial settling, and curing. Mechanics of NH3 release in the three periods were quantitatively analyzed for the first time. Convective mass transfer caused by air movement dominated NH3 release in the first two periods. In the curing period, due to decreased moisture content and filled capillaries in the concrete, diffusion of NH3 from inside of concrete to its surface became the rate-limiting factor. Diffusivity of the mixing period and the initial settling period was 9.1 × 10−8 (±1.25 × 10−7) and 3.93 × 10−9 (±2.78 × 10−9) m2/s, respectively. In the curing period, NH3 diffusivity in the concrete continuously decreased, ranging from 5.36 × 10−9 m2/s to below detection limit in 3 weeks. The difference in diffusivity among different periods reflected the physical and chemical change of the concrete.
机译：为了表征从氨化粉煤灰在混凝土中释放的氨（NH3），进行了室内实验，在混凝土中添加了铵含量为65至3200 mg NH4 + / kg粉煤灰的粉煤灰。给出了混凝土中NH3释放的物理描述，并建立了定量扩散模型。在实验中，氨气释放持续了5天到3周。氨气释放速率逐渐降低到不可检测的水平后，混凝土中仍保留有20％至70％的铵。在释放的所有NH3气体中，混合混凝土后的前8小时排放了80％以上的氨。根据混凝土的物理和化学条件，从混凝土中释放出的NH3分为三个阶段：混合，初始沉降和固化。首次定量分析了这三个时期中NH3释放的机理。由空气流动引起的对流传质在前两个时期主要是NH3的释放。在养护期间，由于混凝土中的水分含量降低和毛细血管充填，NH 3从混凝土内部向其表面的扩散成为限速因素。混合时间和初始沉降时间的扩散率分别为9.1××10-8（±1.25××10-7）和3.93××10-9（±2.78××10-9）×m2 / s。在养护期间，在3周内，混凝土中的NH3扩散率不断降低，从5.36××10-9 m2 / s降至检测极限以下。不同时期之间扩散率的差异反映了混凝土的物理和化学变化。

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  • 来源
    《Air quality, atmosphere & health》 |2014年第4期|505-513|共9页
  • 作者

    Lin Shou; Joshua Hayes; Weizhi Cheng; Chang-Yu Wu; Timothy Townsend; Tim Vinson; John Schert;

  • 作者单位

    1.Department of Environmental Engineering Sciences Engineering School of Sustainable Infrastructure and Environment University of Florida 406 AP Black Hall PO Box 116450 Gainesville FL 32611-6450 USA;

    1.Department of Environmental Engineering Sciences Engineering School of Sustainable Infrastructure and Environment University of Florida 406 AP Black Hall PO Box 116450 Gainesville FL 32611-6450 USA;

    1.Department of Environmental Engineering Sciences Engineering School of Sustainable Infrastructure and Environment University of Florida 406 AP Black Hall PO Box 116450 Gainesville FL 32611-6450 USA;

    1.Department of Environmental Engineering Sciences Engineering School of Sustainable Infrastructure and Environment University of Florida 406 AP Black Hall PO Box 116450 Gainesville FL 32611-6450 USA;

    1.Department of Environmental Engineering Sciences Engineering School of Sustainable Infrastructure and Environment University of Florida 406 AP Black Hall PO Box 116450 Gainesville FL 32611-6450 USA;

    2.Hinkley Center for Solid and Hazardous Waste Management 528 Nuclear Science Building PO Box 116016 Gainesville FL 32611-6016 USA;

    2.Hinkley Center for Solid and Hazardous Waste Management 528 Nuclear Science Building PO Box 116016 Gainesville FL 32611-6016 USA;

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  • 正文语种 eng
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  • 关键词

    Ammoniated fly ash; Concrete; Ammonia; Diffusivity; Notation;

    机译：氨化粉煤灰;混凝土;氨气;扩散率;符号;

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