Study on Packing and Mechanical Properties of Granular Composities Material

• Main Authors: Lin Ping-Ju, 林秉如
• Other Authors: Ta-Peng Chang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/68525528389820982382

博士 === 國立臺灣科技大學 === 營建工程系 === 88 === The research aimed at investigating the relationship of the granular composite packing and dry-nodded unit weight, the study of interface properties and the influence of interface on the mechanical properties of composite material as well. The comparison of theoretical values and the experimental values was investigated. Packing aspect : The research presents a theoretical equation and graphic approach to obtain the dry-nodded unit weight of the packing with the least void ratio and the fine aggregate ratio. The theoretical results indicate if that both fine and coarse aggregate have same specific gravity, the point of maximum dry-nodded unit weight is same as that of the least void ratio on the curve of the dry-nodded unit weight verse fine aggregate ratio. The experimental results show that the least void ratio for both of the cold-pelletized lightweight aggregate and the normal-weight sand packing are 0.352, and 0.335, 0.251, and 0.234 for the sintered lightweight aggregates of types I, II, III respectively. The more even of grain distribution (sintered type II) or the smaller of grain size (sintered type III) of aggregate packing with the less of void ratio has the denser of packing structure. The mechanical properties of composite material aspect: The research presents a theoretical equation to predict of the strength and elastic modulus for three-phase composite material. The theoretical mode and numerical analysis results indicate that the elastic modulus of composite material can be effectively improved by increasing grain content, decreasing the volume of interface and increasing the elastic modulus of composition. The elastic modulus ratio of composite material with 80% and 20% grain content is between 3 to 4.3（Ea/Em=10~100）. The elastic modulus ratio of composite material with 2.5% and 90% content of interface volume is about 1.82（grain content is 20%, Ea/Em=1.5, Ef/Em=0.5）. Aggregate fracture was found as the HPC specimen broken in the compressive test. The results of numerical analysis show that the strength of composite concrete could be enhanced by increasing the modulus of the aggregate or lowering that of the paste. It could be observed from the result of SP-paste test that the adding of superplasticizer could increase the compressive strength and lower the elastic modulus. The compressive strength and the elastic modulus of the paste without superplasticizer are 59.2 MPa and 22.3 GPa, respectively. The compressive strength and the elastic modulus of the paste with 4% superplasticizer are 102 MPa and 20.9 GPa, respectively. This is reasonably in agreement with the fracture model of HPC. As the strength of interface and aggregate are 0.7 and 1.5 times of strength of matrix, and the elastic modulus of aggregate is more than three times of the elastic modulus of matrix, the strength of composite material is dominated by that of the aggregate. As SEM was used to analyze the interface properties, it was found that there was a larger deviation of component ratio of Ca/Si in the interface. The Ca/Si ratio of the matrix ( W/C=0.36) is about 2.5. The HV of interface is lower than that of matrix. The HV of matrix ( W/C=0.36) is 32.9. If the elastic modulus of interface for the granite concrete(Gr2) is between 0.55 to 0.6 Em, the present theoretical three-phase model predicts that the concrete will be failed at the interface, which complied with the failure mode for normal concret.