冲击荷载作用下氧化石墨烯改性珊瑚砂浆的动态力学特性与微观机制

Dynamic mechanical properties and microscopic mechanism of graphene oxide modified coral mortar under impact load

珊瑚砂是我国南海岛礁应急工程的首选建筑材料,但因其具有疏松多孔、强度低、易破碎等缺陷,珊瑚砂浆的整体力学性能难以满足设计要求。氧化石墨烯(GO)可有效改善珊瑚砂浆的力学性能,然而,目前关于冲击荷载作用下GO改性珊瑚砂浆的动态力学特性研究少有涉及。本文通过开展改性珊瑚砂浆的冲击压缩试验与微观结构试验,分析了不同氧化石墨烯掺量和不同应变率条件下改性珊瑚砂浆动态力学性能的变化规律及其微观机制。结果表明:(1)珊瑚砂浆的动态应力-应变曲线近似呈四段式,其变化趋势受GO掺量和应变率影响显著;(2)在相同应变率条件下,珊瑚砂浆的动态抗压强度随GO掺量的增加均呈先增加后降低的变化特征,且在GO掺量为0.03wt%时达到最大值;(3)珊瑚砂浆的动态增强因子(DIF)和韧性指数具有明显的应变率效应;(4)GO可定向驱使水化产物充填砂浆裂隙或孔隙,提高结构完整性,增强珊瑚砂浆抗冲击性能。

Coral sand is widely used as a preferred building material for emergency projects of reef islands in the South China Sea.The mechanical properties of coral mortar are normally low due to the loose porosity,low particle strength and easy breakage of coral sand,making it hard to meet the requirements of practical projects.It is well recognized that graphene oxide(GO)can effectively improve the mechanical properties of coral mortar,but limited studies focus on the dynamic mechanical properties of GO-modified coral mortar under impact loads.In this study,a series of impact compression tests and microscopic tests were conducted on GO-modified coral mortar to investigate effects of GO content and strain rate on its dynamic mechanical properties and microscopic behaviors,respectively.Experimental results demonstrate that stress-strain curves of coral mortar could be approximately divided into four stages,and the development patterns of the curves were combinedly influenced by GO content and strain rate.The dynamic compressive strength of GO-modified coral mortar firstly increases and then decreases with increasing GO content,with a maximum value at 0.03wt%of GO content.Also,the dynamic strengthening factor(DIF)and toughness index of GO-modified coral mortar show obvious strain-rate effects.Microstructural observations imply that the addition of GO could drive hydration products to fill the cracks or large pores inside coral mortar,leading to improvements in its structural integrity and impact resistance performance.