碳纳米管增强粉煤灰泡沫混凝土的制备及变形特性

Preparation and Deformation Characterization of Carbon Nanotube-Reinforced Fly Ash Foamed Concrete

为满足泡沫混凝土作为隧道围岩支护预留变形层填充介质力学性能要求,研制了一种微量碳纳米管增强粉煤灰泡沫混凝土(CNTAFC)的新型变形层填充材料。基于单因素分析,利用Box-Behnken Design响应面法,建立CNTAFC抗压强度预测模型,对其制备参数进行优化。此外,联合单轴压缩试验与数字散斑采集技术,对CNTAFC试样的荷载变形特征进行研究。结果表明:CNTAFC抗压强度回归模型合理有效,当碳纳米管(CNTs)掺量0.13%,骨胶比24.75%,粉煤灰掺量70.57%时,其28 d抗压强度预测值最大为5.936 MPa,误差为2.54%;CNTAFC试样提高了峰值强度,延性增强,其平均峰后强度大于峰值强度的60%,峰后曲线应变范围占极限应变的30%以上,满足围岩卸压吸能材料的性能要求;CNTAFC变形局部化启动可分为应变条件和应力条件,且选择应变确定条件为宜;在变形局部化启动时,CNTAFC强度接近峰值强度,泊松比显著提升。

To meet the mechanical performance requirements of foam concrete as the filling material for the reserved deformation layer of tunnel surrounding rock support,a novel deformable filling material called micro carbon nanotubes reinforced fly ash foam concrete(CNTAFC)was developed.The preparation parameters of CNTAFC were optimized by establishing a compressive strength prediction model using the Box-Behnken Design response surface methodology based on single factor analysis.Furthermore,the load deformation characteristics of CNTAFC specimens were investigated through a combination of uniaxial compression tests and digital speckle correlation measurement(DSCM).Results demonstrate the reasonability and effectiveness of the CNTAFC compressive strength regression model.With a CNT(carbon nanotube)content of 0.13%,a bone-cement ratio of 24.75%,and a fly ash content of 70.57%,the predicted 28-day compressive strength is 5.936 MPa,with an error of 2.54%.The CNTAFC sample exhibits improved peak strength and enhanced ductility.The average post-peak strength exceeds 60%of the peak strength,and the post-peak strain range accounts for over 30%of the ultimate strain.These characteristics satisfy the performance requirements for pressure relief and energy absorption in surrounding rock.The localized initiation of CNTAFC deformation can be distinguished under strain and stress conditions,of which the strain condition is more appropriate for determining deformation localization.When deformation localization is activated,the CNTAFC strength approaches its peak strength,and the Poisson’s ratio increases significantly.