Rapid and economical method for assessing metakaolin quality as SCM for low carbon binders

IF 3.9 3区 工程技术 Q2 CONSTRUCTION & BUILDING TECHNOLOGY
Mehnaz Dhar, Shashank Bishnoi
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引用次数: 0

Abstract

While the assessment of the quality of clay calcination for use in cements is important to ensure optimal performance, the currently available test methods, such as lime-reactivity, R3, XRD, TGA, etc. do not meet the requirements for a quick and cost-effective quality control at industrial clay calcination units. This paper proposes the use of a combination of methylene blue and density measurements to obtain reliable assessment of the quality of calcination of kaolinite-rich clays. Seven different clays calcined within the temperature range of 400 °C to 1000 °C were studied using these techniques and the results were compared with traditional methods. The results clearly demonstrate that the degree of conversion of kaolinite to metakaolin can be effectively obtained by measuring the residual kaolinite-content using the methylene blue test. A 50% reduction in the methylene blue value indicates the presence of under-calcined clay. Additionally, the formation of the spinel phase, which is the first unreactive product that forms upon over-calcination, can be identified by density measurements, as it is associated with higher density values. The proposed test methods can be implemented at clay-calcination units without the need for expensive equipment and highly-skilled technicians. The methods are seen to be sufficiently quick and reliable for a continuous monitoring of the calcination quality at short intervals.

低碳粘结剂用偏高岭土质量快速经济评价方法
虽然对水泥用粘土煅烧质量的评估对于确保最佳性能非常重要,但目前可用的测试方法,如石灰反应性、R3、XRD、TGA等,不能满足工业粘土煅烧装置快速、经济地进行质量控制的要求。本文建议使用亚甲基蓝和密度测量相结合的方法来获得对高岭石粘土煅烧质量的可靠评估。研究了在400℃~ 1000℃温度范围内煅烧的7种不同粘土,并与传统方法进行了比较。结果表明,用亚甲基蓝法测定残余高岭石含量可以有效地获得高岭石向偏高岭石的转化程度。亚甲基蓝值降低50%表明存在未煅烧的粘土。此外,尖晶石相的形成,这是在过度煅烧后形成的第一个非反应产物,可以通过密度测量来识别,因为它与较高的密度值有关。所提出的测试方法可以在粘土煅烧装置上实施,而不需要昂贵的设备和高技能的技术人员。这些方法被认为是足够快速和可靠的,可以在短时间间隔内连续监测煅烧质量。
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来源期刊
Materials and Structures
Materials and Structures 工程技术-材料科学:综合
CiteScore
6.40
自引率
7.90%
发文量
222
审稿时长
5.9 months
期刊介绍: Materials and Structures, the flagship publication of the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), provides a unique international and interdisciplinary forum for new research findings on the performance of construction materials. A leader in cutting-edge research, the journal is dedicated to the publication of high quality papers examining the fundamental properties of building materials, their characterization and processing techniques, modeling, standardization of test methods, and the application of research results in building and civil engineering. Materials and Structures also publishes comprehensive reports prepared by the RILEM’s technical committees.
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