煤矸石粗集料理化性质和形状特征对混凝土强度的影响

随着天然集料的日益缺乏以及国家对固体废弃物再利用的高度重视，煤矸石集料的应用已引起广泛关注，但不同地区煤矸石粗集料理化性质和形状特征差异较大，会显著影响混凝土性能。本文选取陕西省不同矿区的煤矸石，采用宏观指标(压碎指标、吸水率、坚固性、表观密度、含泥量)和细观指标(矿物组成、化学成分、微观形貌和内部孔结构)评价煤矸石粗集料的理化性质，并分析了两者之间的关联性。针对煤矸石与天然碎石的形状差异，提出了球度、角数和纹理指数等煤矸石粗集料形状统计指标，并结合煤矸石粗集料宏观指标分析了对混凝土工作性与强度的影响规律。研究结果表明，石英、高岭石和伊利石含量高、微观形貌密实、孔隙率小的煤矸石粗集料，吸水率和压碎指标较低；与天然碎石相比，煤矸石粗集料球度较低，多呈不规则形状，角数和纹理指数高，表现为棱角较多且尖锐、表面更粗糙；压碎指标和吸水率低的煤矸石集料配制的混凝土，和易性好、强度高；当煤矸石粗集料压碎指标差异小时，其形状统计指标决定了混凝土强度，球度越高、角数和纹理指数越小，混凝土强度越低。

Influence of physicochemical properties and shape characteristics of coal gangue coarse aggregate on concrete strength

Natural aggregate is increasingly scarce, and the reuse of solid waste is highly valued. Application of coal gangue aggregate has been drawing broad attention. However, the performance of coal gangue varies greatly in different regions, and physicochemical properties and shape characteristics of coal gangue coarse aggregate significantly affect the performance of concrete. This paper aims at the coal gangue in different mining areas of Shaanxi Province, The crushing index, water absorption, soundness, apparent density and clay content are taken as the macro indexes of coal gangue coarse aggregate, the mineral composition, chemical composition, microstructure and internal pore structure are taken as the microscopic indexes of coal gangue coarse aggregate, and analyses the association between them. In view of the shape difference between coal gangue and nature gravel, the sphericity, angular number(AN) and aggregate particle shape and texture(IAPST) are proposed as shape statistical indexes of coal gangue coarse aggregate, in order to quantify its shape characteristics. Moreover, The influence of macro indexes and shape statistical indexes of coal gangue on workability and strength of concrete are analyzed. The results show that coal gangue with high content of quartz, kaolinite and illite, dense microstructure and small porosity has low water absorption and crushing index. Compared with natural gravel, the coal gangue coarse aggregate has lower sphericity and more irregular shapes. Most coal gangues have high AN and IAPST, showing more sharp edges and rougher surface. Coal gangue with low water absorption and low crushing index is used as coarse aggregate, and the prepared concrete has good workability and high strength, which can meet the C30 strength grade. Shape statistical indexes of coal gangue coarse aggregate affects the strength of concrete when the crushing indexes of coal gangue coarse aggregate is roughly the same. The higher the sphericity, the smaller angular number and texture index, resulting in the lower concrete strength, which is due to the poor interfacial bonding between coal gangue coarse aggregate and cement.