关键词: 洗选煤矸石, 拌合工艺, 附加水, 预湿时间, 坍落度, 抗压强度

Abstract: Washing coal gangue has the characteristics of many impurities,large porosity and strong water absorption,and the concrete prepared from it has poor fluidity and low strength. In order to solve this problem,the mixing method of washing coal gangue was studied by optimization tests. Firstly,the washing coal gangue fine aggregate was pre-wetting,and then the concrete was mixed by one feeding method. The effect of additional water amount and pre-wetting time on the fluidity and strength of concrete was studied. Finally,scanning electron microscope was used to observe the influence of pre-wetting method on the micromorphology of concrete,and the gray level of the micromorphology was analyzed by Image J. The results showed that with the increase of additional water,the slump of concrete mixture presents an upward trend,and the 7 d and 28 d compressive strength increases with it. The longer the pre-wetting time of coal gangue fine aggregate,the greater the slump of the mixture, and the 7 d and 28 d compressive strength first increased and then decreased. The pre-wetting treatment can promote the formation of more C—S—H gels,improve the microporous structure of concrete,and increase the compactness. Better slump and higher compressive strength can be obtained by adding additional water to the washing coal gangue fine aggregate at 100% of saturated water absorption rate and mixing concrete after 60 minutes of prewetting. The research results are expected to provide theoretical guidance and technical support for the commercial application of washing gangue concrete.

Key words: washing coal gangue,mixing method,additional water,pre-wetting time,slump,compressive strength