Basalt Fibers as composite material for structural elements

Basalt Fibers as composite material for structural elements

Basalt fibre reinforced polymer (BFRP) is an interesting structural material especially in combination with concrete. For instance when designing against thermal shrinkage as in slab on grade, basalt rebars have an advantage in that the thermal expansion coefficient is very close to the thermal shrinkage coefficient of concrete (Williams, 2015).

In an enviromental study of concrete BFRP beams carried out by Wiik, Thorhallsson and Azrague, (2017) one of the core finding was that both BFRP tendons and reinforcement steel bar have similar emission factors: 2,6 and 2,34 kgCO2eq/kg respectively.

However, since BFRP has a lower specific weight than steel, and is three times lighter, the overall embodied emissions are much lower in the BFRP reinforced concrete beams. This is because less material (per kg) is required to perform the same function.

During recent years, the structural and composite laboratory at Reykjavik University (SEL) has performed novel experimental and analytical research using continuous basalt fibers as a structural material in composite timber and concrete structures. (Thorhallsson et. al. 2011, 2012, 2013a, 2013b, 2013c, 2014a, 2014b, 2015, 2016a, 2016b), (Johannesson et. al. 2017). The paper will give an overview of these experiments and draw some general conclusions based on the experience accumulated.

The experimental programs to date, involves the following specimens:

  • Bending test of prestressed basalt fiber reinforced concrete beams.
  • Monitoring of pre-tensioned BFRP bars to estimate loss of prestress.
  • Thin concrete panels with basalt fiber mats as tension reinforcement.
  • Comparative testing of rectangular steel reinforced concrete columns with and without BFRP wrapping for strengthening.
  • Glulam beams strengthened by gluing one-directional basalt mats to the bottom (tension) lamella.
  • Concrete beams with BFRP sheets bonded with mortar on the tension side.
  • Concrete beams with BFRP mats glued on their sides to improve shear strength behaviour.
  • Composite plate specimens produced using basalt fiber mats in polyester resin and tested for tension, compression and shear forces using a standard ASTM test.

In nearly all cases, the experimental results were compared with analytical and/or numerical models. In the following sections a few of the experimental programs listed above are described and the key results summarized.

Authors:

Eyþór Rafn Þórhallsson, Jónas Þór Snæbjörnsson
Reykjavik University

Conference: COST Action TU1207 End of Action Conference, At Budapest, Hungary

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