Abstract

SANCHEZ HENAO, Claudia Patricia; JIMENEZ CASTRILLON, Diego Andrés  and  RUIZ MUNERA, Jorge Ignacio. Use of a biological additive to enhance the physical-mechanical and thermal properties of concrete. Rev.fac.ing.univ. Antioquia [online]. 2006, n.36, pp.96-109. ISSN 0120-6230.

The effect of the addition of a biological ingredient composed primarily of calcific bacteria (T. ferroxidans, T. thioxidans, Desulfovibrio and Sulfolobus acidularios) on the properties of concrete is studied. The biological additive was synthesized based on native cultures in a nutritive medium (modified 9K medium), 2.5 ≤ pH ≤ 3.0, at room temperature in a 30 L bioreactor. Cylinders of concrete containing 30, 60, and 100% of the biological additive were prepared using different aging times (7 and 28 days) in order to determine the technical feasibility of the mixture. The mixture of concrete was prepared using a cement to sand to gravel ratio of 1:2,3:3 and a water to cement ratio of 0.56:1. The sample without biological additive was used as the reference. The main findings are: an increase of 17.2% in resistance was observed in the sample with 30% biological additive (14.63 ± 2.11 MPa and 15.17 ± 0.85 MPa at 7 and 28 days, respectively); the percentage of pores and their diameter decreased by 39% and 46%, respectively, in the sample with 30% biological additive (porosity: 0.91%, pore diameter: 144.7 μm); thermal conductivity decreased in all samples containing the biological additive (the best behavior was obtained in the sample with 30% biological which displayed a 50% reduction in thermal conductivity: 0.33W/m K); Durability to nitric acid indicates that weight lose was larger for the reference probe than for the sample with 30% additive, 0.464 ± 0.012 g and 0.326 ± 0.028 g, respectively.

Keywords : bioreinforcement; porosimetry; thermal conductivity; calcific bacteria; durability.

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