基于新型损伤变量的多尺度改性混凝土性能分析及评定

Multi-scale Modified Concrete Performance Analysis and Evaluation Based on New Damage Variables

考虑普通混凝土在性能上存在的天然缺陷,提出在“纳米-微米-毫米”多个尺度上采用不同级别外掺材料改善混凝土性能的设计理念.基于该理念,选用碳纳米管、碳酸钙晶须、聚乙烯醇(PVA)纤维、钢纤维和橡胶颗粒设计并完成多组多尺度改性混凝土的单轴压缩试验.结合目前损伤本构的研究不足,从耗能角度提出基于能量法的损伤变量和损伤本构.为综合评估混凝土力学性能,提出考虑混凝土抗压强度的修正损伤变量.分析结果表明:碳纳米管、碳酸钙晶须、PVA纤维和钢纤维的掺入能够有效改善混凝土的力学性能,而橡胶颗粒的掺入会导致混凝土抗压强度大幅降低;与基于Weibull分布的损伤变量和损伤本构相比,基于能量法的损伤变量和损伤本构能更真实反映混凝土的损伤状态和性能特征;采用修正损伤变量对混凝土综合力学性能进行评估得到的结果合理可信.

Considering the natural defects in the performance of concrete,the design concept of adopting different sizes materials to improve the performance of concrete on the“nano-micron-millimeter”scale is proposed.Based on this concept,carbon nanotubes,calcium carbonate whiskers,polyvinyl alcohol(PVA)fibers,steel fibers and rubber particles are selected to design and complete the uniaxial compression test of multi-scale modified concrete.Combined with the deficiency of the current research on the damage constitutive model,the damage variable and damage constitutive model based on the energy method are proposed from the perspective of energy consumption.In order to comprehensively evaluate the mechanical properties of concrete,a modified damage variable considering the compressive strength of concrete is proposed.The results show that carbon nanotubes,calcium carbonate whiskers,PVA fibers and steel fibers can effectively improve the mechanical properties of concrete,while rubber particles can reduce the compressive strength of concrete.Compared with the damage variable and damage constitutive model based on Weibull distribution,the damage variable and damage constitutive model based on the energy method can more truly reflect the damage state and performance characteristics of concrete.Evaluation results of concrete comprehensive mechanical properties obtained by modified damage variables are reasonable and credible.