Thermal activation and mechanical properties of high alumina coal gangue as auxiliary cementitious admixture
MATERIALS RESEARCH EXPRESS(2024)
摘要
In order to use high alumina coal gangue as auxiliary cementitious admixture via a simple and convenient thermal activation technique, the thermal transformation, mineral phase transformation and structure changes of coal gangue at calcining temperatures of 500-1000 degrees C were analyzed using x-ray diffraction (XRD), differential thermal Analysis (DTA), thermogravimetry (TG), infrared analysis (IR) and scanning electron microscope (SEM). The mechanical properties of cement mortar with 30% coal gangue auxiliary cementitious admixture were also measured to determine the optimal calcining temperature. As calcining temperature was increased, the coal gangue experienced the following transformations: carbon combustion, dehydroxylation, metakaolin transformation and mullite transformation. The cement mortar with coal gangue auxiliary cementitious admixture calcined at 700 degrees C presented the highest 28-d flexural and compressive strength, increasing by 8.27% and 11.85% respectively as compared with the benchmark cement mortar. The maximum dosage of coal gangue auxiliary cementitious admixture in cement mortar was further identified to be less than 30% by mechanical properties testing. The activity of high alumina coal gangues at different calcining temperatures was explained from the view points of hydration degree and products. The present investigation can provide a useful reference to utilize high alumina coal gangue as auxiliary cementitious admixture by means of a simple thermal activation at 700 degrees C.
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关键词
high alumina coal gangue,kaolinite,thermal activation,mechanical properties,microstructure,cementitious admixture
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