Study On Adhesion Rule Of Cement Paste,Characteristics Of Cementing Structure And Mechanical Behavior Of Cemented Granular Materials

Cement matrix deposited on grain-to-grain contacts has a dramatical influence on the mechanical behavior of cemented granular materials,and significantly improve the mechanical properties.The mechanical behavior of cemented granular materials depends on the cement matrix volume and cementing structure,and the deposition characteristic of cement paste is related to its rheological behavior.Based on granular material column flowing test,the relationship between rhelogical behavior of cement paste and deposition amount was explored.And then,the relation between cement matrix volume and cement matrix morphology was investigated with high precision X-ray CT scanning technique.Moreover,a formula between peak strength of cemented granular materials and cement matrix volume fraction was theoretically deduced,and the influence of cement matrix volume on mechanical behavior was studied with uniaxial compression test.The mian findings are concluded as follow.1.The mini-slump flow tests and granular material column flowing tests were adopted to study the deposition characteristic of self-compacting cement paste flowing through granular materials.The relation between mini-slump flow value and deopistion amount were established.Based on the Bingham fluid theory,the effect of yield stress and viscosity of cement paste on the deopistion amount was analyzed.The deposition mechanism of the self-compacting cement paste flowing through granular materials is concluded,which relies on the yield stress when the filtration is negligible.2.The morphology of cement matrix and spatial distribution of selfcompacting cement paste deposited in granular materials were investigated by high precision X-ray CT scanning.A novel CT image processing algorithm was proposed to precisely separate particle,cement matrix and void.The results showed that the self-compacting cement paste flowing granular materials forms ramified objects,which is different with wet granular materi als.The cement matrix morphology relies on the depositon amount.In another word,the cement matrix morphology depends on the rheological properties of self-compacting cement paste.The matrix morphology of self-compacting cement paste in granular materials includes capillary bridges,trimer,filling tetrahedron and pentamer.Self-compacting cement paste with low flowability will fill the void,and the cement matrix merges into a larger matrix cluster.3.Based on the the microscopic failure mechanism of cemented granular materials,a formula between peak strength and matrix volume fraction was theoretically deduced for cemented granular materials,and it was verified with experimental tests.The stress-strain curves of cemented granular materials were obtained by uniaxial compression tests.The results indicated that Young's modulus,the strain and energy release at failure linearly increase with the increase of matrix volume fraction.4.The internal broken characteristics of cemented granular materials d uring uniaxial compression loading were studied with acoustic emission technology,and the surface deformation charactisitics were captured with digital camera.The beginning time of acoustic emission signal and failure mode relies on the cement matrix volume fraction.Cemented granular materials with a low value of matrix volume fraction occur shear failure,and a marked “barreling” failure occurs for the samples with higher value of matrix volume fraction.