Aggregate production: Fines generation during rock crushing

The energy required to crush rocks is proportional to the amount of new surface area that is created; hence, a very important percentage of the energy consumed to produce construction aggregates is spent in producing non-commercial fines. Data gathered during visits to quarries, an extensive survey and laboratory experiments are used to explore the role of mineralogy and fracture mode in fines production during the crushing of single aggregates and aggregates within granular packs. Results show that particle-level loading conditions determine the failure mode, resulting particle shape and fines generation. Point loading (both single particles and grains in loose packings) produces clean fractures and a small percentage of fines. In choked operations, high inter-particle coordinationcontrolsparticle-levelloadingconditions,causesmicro-fracturesonnewaggregatefacesandgeneratesalargeamountof fines. The generation of fines increases when shear is imposed during crushing. Aggregates produced in current crushing operations show the effects of multiple loading conditions and fracture modes. Results support the producers' empirical observations that the desired cubicity of aggregates is obtained at the expense of increased fines generation when standard equipment is used. © 2006 Elsevier B.V. All rights reserved.

[1]  Theodor Zingg,et al.  Beitrag zur Schotteranalyse , 1935 .

[2]  Paul Tapponnier,et al.  Development of stress-induced microcracks in Westerly Granite , 1976 .

[3]  Aw Drews,et al.  Standard Test Method for Analysis of , 1998 .

[4]  Jerry A. Yamamuro,et al.  DRAINED SAND BEHAVIOR IN AXISYMMETRIC TESTS AT HIGH PRESSURES , 1996 .

[5]  R. Bathurst,et al.  Analytical study of induced anisotropy in idealized granular materials , 1989 .

[6]  J. Gramberg,et al.  A non-conventional view on rock mechanics and fracture mechanics , 1988 .

[7]  T. M. Bodas Freitas,et al.  Particle breakage during shearing of a carbonate sand , 2004 .

[8]  Malcolm D. Bolton,et al.  On the micromechanics of crushable aggregates , 1998 .

[9]  G McNally,et al.  Soil and Rock Construction Materials , 1998 .

[10]  W. Brace,et al.  Direct observation of microcavities in crystalline rocks , 1974 .

[11]  Yukio Nakata,et al.  MICROSCOPIC PARTICLE CRUSHING OF SAND SUBJECTED TO HIGH PRESSURE ONE-DIMENSIONAL COMPRESSION , 2001 .

[12]  R. D. Barksdale.  The Aggregate Handbook , 1991 .

[13]  Mark Randolph,et al.  Compression and crushing behaviour of calcareous soils , 2000 .

[14]  Glenn R. McDowell,et al.  Fractal compression of soil , 2001 .

[15]  W. C. Krumbein,et al.  Stratigraphy and sedimentation , 1963 .

[16]  Iraj Farhoomand,et al.  Compressibility and crushing of granular soil in anisotropic triaxial compression , 1967 .

[17]  Arcady Dyskin,et al.  Mechanics of 3-D crack growth under compressive loads , 1996 .

[18]  Antonio Bobet,et al.  Modeling of Crack Initiation, Propagation and Coalescence in Uniaxial Compression , 2000 .

[19]  B. Hardin,et al.  Crushing of Soil Particles , 1985 .

[20]  R. Kranz,et al.  Crack-crack and crack-pore interactions in stressed granite , 1979 .

[21]  María Guimaraes.  Crushed stone fines and ion removal from clay slurries-fundamental studies , 2002 .

[22]  Kenneth L. Lee,et al.  Drained Strength Characteristics of Sands , 1967 .

[23]  Luis E. Vallejo,et al.  Discrete Element Method Evaluation of Granular Crushing Under Direct Shear Test Conditions , 2005 .

[24]  M. Bolton,et al.  The fractal crushing of granular materials , 1996 .

[25]  S. Rampello,et al.  Pre-failure deformation characteristics of geomaterials , 1999 .

[26]  Julio R. Valdes,et al.  Fines migration and formation damage - microscale studies , 2002 .