Zaffar Suhail, Kumar Aneel, Memon Naeem Aziz, Kumar Rabinder, Saand Abdullah
Department of Civil Engineering, Faculty of Architecture & Civil Engineering, Mehran University of Engineering and Technology, Jamshoro 76062, Pakistan.
Department of Civil Engineering, Faculty of Engineering, Quaid-e-Awam University of Engineering, Science & Technology, Nawabshah 67480, Pakistan.
Materials (Basel). 2022 Mar 21;15(6):2320. doi: 10.3390/ma15062320.
This research was performed to investigate the optimum conditions for developing pozzolanic ashes from organic wastes to be used as cement replacement materials. The organic wastes explored in the research are rice husk ash (RHA), wheat straw ash (WSA), and cow dung (CDA). When the organic waste is turned into ash, it develops a pozzolanic character due to the presence of silica. However, the presence of reactive silica and its pozzolanic reactivity depends on the calcination temperature, duration, and grinding. In this research, the organic wastes were calcined at three different calcination temperatures (300 °C, 400 °C, and 800 °C) for 2, 4, 6, and 8 h duration. The obtained ashes were ground for 30 min and replaced by 20% with cement. The samples containing ashes were tested for compressive strength, X-ray diffractometry (XRD), weight loss, and strength activity index (SAI). It was observed that the RHA calcinated at 600 °C for 2 h showed better strength. However, in the case of WSA and CDA, the most favorable calcination condition in terms of strength development was obtained at 600 °C for 6 h duration. The highest SAI was achieved for the mortar samples containing CDA calcinated at 600 °C for 6 h duration (CDA600-6H). The other two ashes (RHA and WSA) did not qualify as pozzolan according to the ASTM C618 classification. This was due to the presence of silica in crystalline form and lower surface area of the ash material. In this research, the ash was ground only for 30 min after calcination which did not contribute to an increase in the specific surface area and thus the pozzolanic activity. The materials ground for the higher duration are recommended for higher SAI.
本研究旨在探究将有机废弃物转化为火山灰质灰分以用作水泥替代材料的最佳条件。本研究中所探究的有机废弃物为稻壳灰（RHA）、麦秸灰（WSA）和牛粪灰（CDA）。当有机废弃物转化为灰分时，由于二氧化硅的存在，它会呈现出火山灰特性。然而，活性二氧化硅的存在及其火山灰反应活性取决于煅烧温度、持续时间和研磨情况。在本研究中，将有机废弃物在三个不同的煅烧温度（300℃、400℃和800℃）下煅烧2、4、6和8小时。将得到的灰分研磨30分钟，并用其以20%的比例替代水泥。对含有灰分的样品进行抗压强度、X射线衍射（XRD）、失重和强度活性指数（SAI）测试。结果发现，在600℃下煅烧2小时的稻壳灰表现出更好的强度。然而，对于麦秸灰和牛粪灰而言，就强度发展而言，最有利的煅烧条件是在600℃下煅烧6小时。对于在600℃下煅烧6小时的含有牛粪灰的砂浆样品（CDA600 - 6H），其SAI最高。根据ASTM C618分类，另外两种灰分（稻壳灰和麦秸灰）不符合火山灰质材料的标准。这是由于灰分材料中存在结晶形式的二氧化硅且比表面积较低。在本研究中，灰分在煅烧后仅研磨了30分钟，这无助于比表面积的增加，从而也无助于火山灰活性的提高。建议对研磨时间更长的材料进行更高的SAI测试。
