玄武岩纤维泡沫混凝土抗冻融性能

Freeze-thaw resistance of basalt fiber reinforced foam concrete

  • 摘要: 在0、25、50和75次冻融循环条件下,对不同密度(600 kg/m31000 kg/m3)和纤维掺量(0、0.15%、0.30%和0.45%)的玄武岩纤维泡沫混凝土试样(Basalt fiber reinforced foam concrete, BFRFC)进行了单轴压缩-声发射联合试验,并基于声发射RA-AF值分布规律、b值变化曲线以及三个宏观抗冻性能指标(吸水率、质量损失率、相对动弹性模量),探究了BFRFC冻融劣化损伤特征与抗冻性能变化规律。结果表明:BFRFC单轴压缩过程中的应力-应变关系曲线具有明显阶段性;冻融循环会导致试样整体强度下降,开裂加快,内部剪切破坏占比提高,而增加玄武岩纤维掺量和材料密度均能够提高试样的峰值承载力(0、25、50和75次冻融循环下最高分别达到11.14 MPa、10.20 MPa、8.741 MPa、7.498 MPa),抑制峰值强度的损失(最多可降低17.9%),提高张拉破坏占比(最多可提高32.4%),延缓试件破坏;另外,随冻融循环次数的增加,BFRFC的吸水率和质量损失率增大,相对动弹性模量下降,相比之下,高密度和高纤维掺量BFRFC的吸水率和质量损失率更小、相对动弹性模量更大,75次冻融循环下质量损失率和相对动弹性模量仍能分别保持在3%以下和70%以上,抗冻性能更佳。

     

    Abstract: Uniaxial compression-acoustic emission combined tests were conducted on basalt fiber reinforced foam concrete specimens (BFRFC) with different densities (600 kg/m3 and 1000 kg/m3) and fiber admixtures (0, 0.15%, 0.30%, and 0.45%) under the conditions of 0, 25, 50, and 75 freeze-thaw cycles. And based on the distribution law of acoustic emission RA-AF values, the b-value change curve as well as three macroscopic freezing performance indexes (water absorption, mass loss rate, and relative dynamic elastic modulus), the damage characteristics and freezing performance change rule of each grade of BFRFC under freeze-thaw environment were investigated. The results show that the stress-strain relationship curves during uniaxial compression of BFRFC have obvious stages. Freezing and thawing cycles lead to a decrease in the overall strength of the specimen, accelerated cracking, and an increase in the percentage of internal shear damage, whereas increasing both the basalt fiber doping and the material density can increase the peak load carrying capacity of the specimen (up to 11.14 MPa, 10.20 MPa, 8.741 MPa, and 7.498 MPa under 0, 25, 50, and 75 freezing and thawing cycles, respectively), inhibit the loss of the peak strength (up to 17.9%), increasing the percentage of tension damage (up to 32.4%) and delaying specimen damage. In addition, with the increase of the number of freeze-thaw cycles, the water absorption and mass loss rate of BFRFC increase, and the relative dynamic elastic modulus decreases. In contrast, the water absorption and mass loss rate of high-density and high-fiber doped BFRFC are smaller, the relative dynamic elastic modulus is larger, and the mass loss rate and relative dynamic elastic modulus can be kept below 3% and above 70% respectively under 75 freeze-thaw cycles, which has better frost resistance.

     

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