冻融环境下玄武岩纤维泡沫混凝土损伤-声发射特征

Damage-acoustic emission characterization of basalt fiber foam concrete under freeze-thaw environment

  • 摘要: 对600和1000密度下4种不同玄武岩纤维掺量(0%、0.15%、0.30%和0.45%)泡沫混凝土(BFRFC)试样进行不同冻融环境下(0、20、40、60和80次冻融循环)单轴压缩联合声发射试验,探究了密度、纤维掺量、冻融循环次数对BFRFC单轴压缩性能的影响,并依据声发射与单轴压缩试验参数建立冻融环境下BFRFC受压损伤本构模型,定量分析不同冻融循环下BFRFC的损伤。结果表明:BFRFC在受压过程有明显的阶段性,分为密实、弹性、屈服和平台四个阶段,声发射特征呈现出接触期、陡增期和缓增期三个阶段;不同冻融循环次数下各试样的强度损失率范围为3.4%~63.6%;冻融环境会降低声发射的活跃度,严重影响BFRFC力学性能;玄武岩纤维掺入使试样累计振铃数先增加后减小,能在一定程度上减缓峰值强度的损失;冻融循环加速裂纹开展,玄武岩纤维可有效抑制裂纹发展,但高掺量时纤维团聚现象凸显,内部损伤加剧;BFRFC在受压前期损伤较低,在相对峰值应力大于0.7时损伤发展加速,直至破坏。

     

    Abstract: The uniaxial compression-acoustic emission tests were carried out on four different basalt fiber admixture (0%, 0.15%, 0.30%, and 0.45%) foam concrete (BFRFC) specimens at 600 and 1000 densities in different freeze-thaw environments (0, 20, 40, 60, and 80 freeze-thaw cycles) to investigate the effects of density, fiber admixture, and number of freeze-thaw cycles on the uniaxial compression performance of BFRFC. The compression damage model was established based on the acoustic emission and uniaxial compression parameters to quantitatively analyze the damage of BFRFC under different freezing and thawing cycles. The results show that: BFRFC has obvious stages in the compression process, which are divided into four stages of dense, elastic, yield and platform, and the acoustic emission characteristics show three stages of contact, steep increase and slow increase; the strength loss rate of each specimen under different numbers of freezing and thawing cycles ranges from 3.4% to 63.6%; the freezing and thawing environment would reduce the activity of acoustic emission, which would seriously affect the mechanical properties of BFRFC; basalt fiber doping causes the cumulative ringing number of the specimen to increase and then decrease, which could slow down the loss of peak strength to a certain extent; Freeze-thaw cycle accelerates the crack development, basalt fibers could effectively inhibit the development of cracks, but the fiber agglomeration phenomenon is highlighted at high doping, and the internal damage is aggravated; The damage of the BFRFC in the pre-pressure stage is low, and the damage development is accelerated at the relative peak stress of more than 0.7, until the damage is damaged.

     

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