风积砂混凝土基本力学性能及影响机理研究

Study on the Mechanical Properties Effect Mechanism of Aeolian Sand Concrete

摘要:

以不同质量分数风积砂代替河砂试配混凝土，研究风积砂混凝土的基本力学性能，揭示影响机理，构建强度模型。用核磁共振（NMR）技术分析了混凝土内部孔隙演变特征，用CT切片法探测了受荷面初始损伤，用扫描电镜（SEM）表征了界面过度区（ITZ）结构形态及水化产物微观形貌。基于美国ACI经验模型，构建了考虑砂子细度模数或是比表面积变化的强度预测模型。结果表明，风积砂掺量为20%时，混凝土力学性能最优。适量风积砂改善混凝土强度的机理在于其优化了颗粒级配，改善了混凝土内部孔径分布范围及ITZ结构，减小了受荷面初始损伤。建立的强度预测模型与试验结果吻合度较高。

Abstract:

River sand was replaced by aeolian sand partly in concrete to study the influence mechanism of aeolian sand on the strength of concrete and establish the prediction model of concrete strength. The internal pore structure of aeolian sand concrete was tested by nuclear magnetic resonance (NMR), the initial damage of bearing surface was detected by the slicing of CT and the structural form of interface transition zone (ITZ) and the hydration product microstructure were characterized by scanning electron microscopy (SEM). A concrete strength prediction model considering the fineness modulus or specific surface area of sand changing was built based on the American ACI model. The results show that the concrete had the highest strength with an aeolian sand content of 20%. The influence mechanism why a proper amount of aeolian sand increasing the strength of concrete is that it optimized the particle gradation of aggregate, improved the internal pore size distribution and the ITZ structure of concrete, as well as reduced the initial damage of the bearing surface. The theoretical prediction model agrees well with the experimental results.