Static compressive failure mechanism and strength prediction of coal gangue concrete
s:To clarify the strength variation law and failure mechanism of coal gangue concrete,a com-bination of experimental research and model prediction was adopted.Through the cube compressive strength test,the failure process,failure mode,size effect,and the influence of water cement ratio on the compressive strength of coal gangue concrete were revealed.The mathematical relationship between wa-ter cement ratio and compressive strength was analyzed,and a GM(1,1)model was established by u-sing grey theory to predict the compressive strength of coal gangue concrete.The results show that coal gangue has the characteristics of most clay rocks,that is,it has good strength when dry and is prone to disintegration after immersion in water.The failure of coal gangue concrete can be divided into three stages(crack generation stage,crack development and expansion stage,concrete failure stage)and three forms(coarse aggregate failure,bonding failure,cement stone failure,and mainly coarse aggregate fail-ure).When the water cement ratio decreases from 0.60 to 0.25,the compressive strength of coal gangue concrete increases by 2.67%to 18.50%,meeting the four strength levels of C15,C20,C25,and C30.Due to the poor physical properties of coal gangue,the transition zone of the concrete inter-face is filled with a large number of micro cracks and pores,resulting in a stronger size effect of coal gangue concrete than ordinary concrete.The predicted values of the GM(1,1)model are basically con-sistent with the measured values,and the accuracy level of the prediction model is level 1.The grey theory can effectively predict the strength growth law of coal gangue concrete,and the grey model can be used to predict the compressive strength of coal gangue concrete before practical application.
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